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BuLLouGu, W. S. 1960. Practical invertebrate anatomy. 2nd ed. London: Macmillan.

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FiscHer, P. H., DuvAL, M. & Rarry, A. 1933. Etudes sur les échanges respiratoires des littorines. Archives de zoologie

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Koun, A. J. 1960a. Ecological notes on Conus (Mollusca: Gastropoda) in the Trincomalee region of Ceylon. Annals and

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Koun, A. J. 1960b. Spawning behaviour, egg masses and larval development in Conus from the Indian Ocean. Bulletin of

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ANNALS OF THE SOUTH AFRICAN MUSEUM

ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM

Volume 99 Band

July 1990 Julie

Part 7 Deel

BENTHIC COMMUNITIES AND

SEDIMENTARY FACIES IN THE

LOWER WITTEBERG GROUP

(DEVONIAN, SOUTH AFRICA)

NORTON HILLER

Cape Town Kaapstad

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C633

BENTHIC COMMUNITIES AND SEDIMENTARY FACIES

IN THE LOWER WITTEBERG GROUP

(DEVONIAN, SOUTH AFRICA)

NORTON HILLER

Department of Geology, Rhodes University, Grahamstown, South Africa

(With 10 figures)

[Paper presented at the Palaeontological Society of southern Africa Symposium, Cape Town,

September 1986]

ABSTRACT

Rare, Middle—Upper Devonian invertebrate fossils are recorded from a few scattered

localities in the lower part of the Witteberg Group. The specimens represent a number of

shallow-water communities similar to those recognized in Silurian and Devonian rocks from

other parts of the world. ~

At a single locality near the top of the Weltevrede Formation near Grahamstown, four

co-existing communities are recognized: a linguloid—orbiculoid community, a Tropidoleptus

community, a homalonotid—Plectonotus community, and a community of largely infaunal

bivalves. Such an assemblage is interpreted as representing the restrictive conditions of an

intertidal flat environment.

Analysis of the sedimentary facies shows that the fossils come from a sequence of

interbedded shales, siltstones and sandstones arranged in a number of thin upward-fining cycles

and displaying flaser, lenticular and wavy bedding. This sequence rests on lithic arenites at the

top of an upward-coarsening unit and is overlain by thick cross-bedded quartz arenites of the

Witpoort Formation. The top part of the Weltevrede Formation is interpreted as having formed

in back-barrier tidal flats during transgressive reworking of a delta top.

In the Western Cape, two localities in the Wagen Drift Formation have yielded a number of

brachiopods, including Tropidoleptus, Australospirifer, chonetaceans and linguloids, as well as

bivalves and possible bryozoa. The greater diversity of this brachiopod assemblage suggests

somewhat deeper water than the Weltevrede Formation assemblage, probably subtidal. The

sedimentary facies of the Wagen Drift Formation are interpreted as having formed in a delta

slope environment. The different interpretations of the faunal assemblages from the two areas

accord well with the different interpretations of the containing sedimentary facies.

CONTENTS

PAGE

AGRO MU CHO Dipamr ree entre an ena in hee SAE Gee MOS vie alg 216

STEN TEYON ONY’ 5 ea 3 SGAGNCUL tb ccs CRO ORTON OP On ee ee es V7

Sedimentary tacteSsa 4). 4. 5 Chg Sai, AE PE ee He rar fe ER 218

FcicA UID aerate eer te My Me ihr a es St orice a Gosedlndunididl @eolep Wid herd DD

PEW EC SCOOT a5. crak dG 6 od lp Ps aH Nne es ea vo eR ae a Jip)

INTE 55 Ble i BR Che otchas Gee ot TE ee ee ee eee 228

(CONES OMNG 6:5 sh Setec a oh de icin ce le ae eee aaa a a rae 228

INGHSCEINGSS cacerousoves of exci GPs cg an ea begat ee ed a a i ee 229

215

Ann. S. Afr. Mus. 99 (7), 1990: 215-230, 10 figs.

216 ANNALS OF THE SOUTH AFRICAN MUSEUM

INTRODUCTION

The Witteberg Group, topmost division of the tripartite Cape Supergroup, is

not noted for its invertebrate fossils, although its plant fossils (Plumstead 1967,

1969) and fish fossils (Jubb 1965; Gardiner 1969) are fairly well documented.

However, rare marine invertebrates have been recovered from a number of

widely spaced localities in the lower part of the group (Fig. 1). Swart (1950)

recorded the presence of the inarticulate brachiopod Lingula and further

indeterminate brachiopods and bivalves in the lowest part of the Witteberg Group

in the Wuppertal area. D. K. Toerien (pers. comm. 1978) recalled finding

brachiopods and trilobites in Witteberg shales at Howison’s Poort, near

Grahamstown, some forty years ago. Theron (1962) described moulds of the

nautiloid Orthoceras and what are possibly bivalve impressions, along with trace

fossils, in rocks of the lower Witteberg Group in the Willowmore district. Loock

(1967) reported the discovery of a ‘Chonetes’ (brachiopod) in sandstones in the

lower divisions of the Witteberg Group near Robertson. Hiller & Dunlevey

(1978) recorded brachiopods, bivalves and possible bryozoa from one of several

localities in the basal unit of the Witteberg Group in the vicinity of Touws River.

Theron (1970, 1972), who had also collected in the Touws River area, used

brachiopods and a trilobite as a basis for assigning a Lower to Middle Devonian

or possibly an Upper Devonian to Lower Carboniferous age to the basal

Witteberg beds.

The purpose of the present study was to re-investigate some of the localities,

in particular those near Grahamstown in the Eastern Cape and near Touws River

in the Western Cape, to see if it was possible to recognize any of the benthic

communities that have been described from Silurian and Devonian rocks from

other parts of the world, and to see if the environmental information provided by

the fossil record was consistent with proposed environmental interpretations

WLo&> SOUTH AFRICA |

Sart fr2 aes

ee =

TR <Q

aS aa

Rook,

a if SS APE

# fossil localities Q__!90_200kilometres

Fig. 1. Map of the major outcrop areas of the Witteberg Group showing the fossil localities.

CT—Cape Town, G—Grahamstown, PE—Port Elizabeth, R—Robertson, TR—Touws

River, WE—Willowmore, WL— Wupperthal.

SEDIMENTARY FACIES IN THE LOWER WITTEBERG GROUP DAT

based on sedimentary facies analysis. Pickerill & Hurst (1983) have pointed out

that the major drawback with many studies that have used fossils to define

depth-associated communities, is that they have lacked complimentary facies

analysis that could provide corroborative evidence for the environmental

assumptions.

STRATIGRAPHY

In the Western Cape, the Wagen Drift Formation is the lowest unit of the

Witteberg Group (Fig. 2). It consists essentially of siltstone and shale with

interbedded sandstones. Hiller & Dunlevey (1978), working in the Touws

River—Montagu area, subdivided that part of the stratigraphy straddling the

Bokkeveld Group—Witteberg Group boundary into three formations, of which

the upper two were placed in the Witteberg Group. The South African Com-

mittee for Stratigraphy (SACS) (1980) regarded these two units as being informal

members within their Wagen Drift Formation. The lower, Nougaspoort Member,

consists of dirty white, red-weathering, unevenly bedded, quartz arenites

separated by thin beds of laminated siltstone. The sandstones show occasional

cross-bedding and contain numerous examples of the trace fossil Zoophycos

(Spirophyton). The upper, Byenest Krans Member, comprises micaceous pale

grey to white mudstones and thin, medium-grained sandstones, with red siltstone

becoming more common towards the top of the unit. In the middle is a thin,

cross-bedded, quartz arenite with Zoophycos traces. The Byenest Krans Member

WESTERN CAPE EASTERN CAPE

WITPOORT

FORMATION Reena

FORMATION

SWARTRUCCENS inn 0) ===

FORMATION eee LL renin Deets

eS WELTEVREDE

ees BLINKBERG FM ara Barre

ea vs marine fossils

WAGEN DRIFT FM

Fig. 2. Stratigraphic columns for the lower part of the Witteberg Group in the Eastern and

Western Cape.

218 ANNALS OF THE SOUTH AFRICAN MUSEUM

has yielded marine invertebrate fossils. from three localities in the vicinity of

Touws River (Boucot et al. 1983).

Overlying the Wagen Drift Formation is the Blinkberg Formation, an

extremely mature quartz arenite unit, which contains some plant fossils. This in

turn, is overlain by the Swartruggens Formation, a relatively thick heterolithic

unit comprising siltstone and shale with thin sandstone interbeds, and containing

plant fossils and Zoophycos traces. The top of the Weltevrede Subgroup is

occupied by the Witpoort Formation, a thick sequence of white-weathering quartz

arenites with thin shale partings and containing plant fossils.

In the Eastern Cape the lateral equivalent of the Wagen Drift, Blinkberg and

Swartruggens formations is the Weltevrede Formation (Fig. 2). It is a thick

succession of shales and siltstones with substantial quartz arenite units, two of

which have been accorded member status. At the base of the formation the

Driekuilen Sandstone Member occupies much the same position as the Nou-

gaspoort Member does in the west, and near the middle of the formation is the

Blinkberg Sandstone Member (SACS 1980). Plant fossils and trace fossils,

including burrows, tracks and trails of various kinds, as well as Zoophycos, have

been found throughout the Weltevrede Formation, whereas the uppermost part

has yielded marine invertebrates. Overlying the Weltevrede Formation, the

Witpoort Formation again consists of thick cross-bedded quartz arenites and thin

carbonaceous shales. Plant fossils and trace fossils have been recorded.

SEDIMENTARY FACIES

In their summary of the depositional environments, Tankard et al. (1982)

stated that the sedimentation in the lower part of the Witteberg Group was

controlled by the continuation of a series of transgressions and regressions that

was established earlier in the Bokkeveld times. The lithofacies are relatively

sandy and similar to those of the Bokkeveld Group, which have been interpreted

as being the deposits of arcuate deltas subject to marine reworking similar to the

present-day Brazos River delta of Texas and the Sao Francisco delta of Brazil

(Tankard & Barwis 1982).

Analysis of the sedimentary facies exposed in Howison’s Poort, near

Grahamstown (Fig. 3), shows that the upper part of the Weltevrede Formation

displays two distinct facies associations. A lower upward-coarsening sequence

consists of interbedded micaceous shales and siltstones displaying lenticular

bedding, passing upward into horizontally laminated and ripple cross-laminated

sandstones (Fig. 4). Load structures are a feature of several sandstone-shale

contacts. This sequence is interpreted as the product of a prograding distributary

mouth bar in a delta complex (Wright 1978). It is overlain by a thin (2 m)

upward-fining sequence that shows ripple cross-laminated sandstone with flaser

bedding at its base, passing upward gradually into shale. Interpretation of this

sequence is made difficult by the fact that it is abruptly truncated by a major erosion

surface, but it is thought to be part of an inter-distributary bay fill (Elliot 1974).

SEDIMENTARY FACIES IN THE LOWER WITTEBERG GROUP 219

SEDIMENT. | GRAIN SIZE PALAEOCURRENT ENVIRONMENTAL STRATIGRAPHIC

COLUMN TRENDS DIRECTIONS INTERPRETATIONS SUBDIVISIONS

BARRIER

A WITPOORT

ths ISLAND

FORMATION

COMPLEX

CHANNELED

WELTEVREDE

TIDAL

FORMATION

n=12

FLATS

DISTRIBUTARY

MOUTH

BAR

Ce a a ee ee

Fig. 3. Stratigraphic log of about 100 m of strata in Howison’s Poort, near Grahamstown.

220 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 4. Top of an upward-coursening sequence in the Weltevrede Formation, Howison’s Poort.

The major erosion surface marks the end of the constructional phase of delta

out-building and the remaining sediments of the Weltevrede Formation were

deposited during a destructional phase. This involved transgressive marine

reworking of the delta top (Fisher et al. 1969). The upper 70 m of the Weltevrede

Formation comprise quartz arenites, siltstones and shales arranged in a number of

upward-fining cycles (Fig. 5). The sandstone units thin upwards and are overlain by

vertical alternations of siltstone and shale in which flaser and lenticular bedding are

common. Trace fossils are common throughout the sequence and marine

invertebrates were recovered from the topmost cycle. The upward-fining cycles are

interpreted as being the products of a tidal-flat environment crossed by meandering

tidal channels (Tankard & Barwis 1982).

The change-over from the Weltevrede Formation to the Witpoort Formation

is thought to mark a major change in shoreline configuration from a lobate or

arcuate deltaic shoreline to a linear barrier-beach shoreline (Johnson 1976). This

change must reflect a reduction in the sediment supply to the shore zone and a

decrease in the rate of subsidence so that marginal marine processes rework and

redistribute the sediment along the shore. Wave reworking of delta front sands

under transgressive conditions produced barrier islands that migrated landwards

over the tidal-flat facies.

The Witpoort Formation consists mostly of mature sandstones. In the basal

10-12 m these are brownish in colour, fine to medium grained, and display

horizontal lamination and ripple cross-lamination. Above this level the

sandstones are cleaner, slightly coarser grained, greyish quartz arenites displaying

planar and trough cross-bedding and horizontal lamination. The lowest sand-

SEDIMENTARY FACIES IN THE LOWER WITTEBERG GROUP 221

Fig. 5. Thin upward-fining sequence near the top of the Weltevrede Formation,

Howison’s Poort.

stones were probably deposited by wash-over processes into the tidal-flat area.

Reinson (1984) has noted that wash-over is one of the main processes by which

barrier islands migrate landward and that scouring associated with wash-over is

responsible for the initiation of new tidal inlets. The clean quartz arenites that

form the bulk of the Witpoort Formation show many of the characteristics of

tidal-inlet channel fill, tidal deltas, and beach and foreshore deposits similar to

Fig. 6. Black carbonaceous shale of lagoonal origin, overlain and underlain by barrier island

sandstones, Witpoort Formation, Howison’s Poort.

222. ANNALS OF THE SOUTH AFRICAN MUSEUM

those described from various modern environments (e.g. Kumar & Sanders 1974;

Hubbard & Barwis 1976; Reddering 1983). The quartz arenite sequence is

interrupted by the development of thin (1m thick) dark grey to black

carbonaceous shales with silty layers, siderite nodules and numerous plant

fragments. These probably formed in stagnant back-barrier lagoonal or marsh

environments (Fig. 6).

A similar detailed facies analysis is not available for the lower part of the

Witteberg Group in the Western Cape but Theron (1970) stated that the basal

Witteberg beds are part of a regressive cycle that follows directly on from similar

cycles in the Bokkeveld Group. Tankard et al. (1982) indicated that the Wagen

Drift Formation represents the subaqueous portion of a delta and that the

overlying quartz arenites of the Blinkberg Formation are the products of

reworking of the delta, much the same as Tankard & Barwis (1982) described

from the Bokkeveld Group.

FAUNA

The two localities within the Wagen Drift Formation near Touws River, from

which material was collected for this study, have yielded an inarticulate bra-

chiopod (Fig. 7E), several articulate brachiopods (Fig. 7D), bivalves and possible

bryozoa. Generally, the preservation of the specimens is rather poor and

identification beyond generic level is very difficult. The inarticulate brachiopod

belongs to the family Lingulidae and specimens in the British Museum (Natural

History) have been identified as Lingula lepta Clarke, aff. Trigonoglossa, and

cf. Barroisella. The specimens in the author’s collection are certainly not

Trigonoglossa, which has a distinctive ornament, and of the other two

identifications Lingula lepta seems the more likely. This is a Brazilian species,

which is also known from the Bokkeveld Group (Reed 1925). Copper (1977),

writing about the Devonian faunas of Brazil, included the species in Dignomia,

presumably on the basis of its relatively large size and thin shell.

Among the articulate brachiopods Australospirifer antarctica (Morris &

Sharpe), Chonetes sp. and Tropidoleptus sp. have been recognized (Boucot et al.

1983). The first of these is well known from the Bokkeveld Group and its Falkland

Islands and South American correlatives. The bivalves are too poorly preserved

for even generic identification.

The assemblage is dominated by prrehibpads but their distribution varies

within the formation. The articulate brachiopods come from the middle of the

unit but recent collecting near the top, just below the junction with the overlying

Blinkberg Formation, yielded only specimens of Lingula lepta.

The Howison’s Poort locality has yielded inarticulate brachiopods, an arti-

culate brachiopod, a homalonotid trilobite, several genera of bivalves, and a

bellerophontid gastropod (Figs 7A—C, 8). The brachiopods include a species of

Lingula, Orbiculoidea baini (Sharpe), which is known from the Bokkeveld

Group, the Falkland Islands and Brazil, and the articulate brachiopod

SEDIMENTARY FACIES IN THE LOWER WITTEBERG GROUP D3

Fig. 7. Brachiopods from the Witteberg Group. A. External mould of a pedicle valve of

Orbiculoidea sp., Weltevrede Formation, Howison’s Poort. x 4. B. Exernal mould of a pedicle

valve of Lingula sp., Weltevrede Formation, Howison’s Poort. xX 2,5. C. Internal mould of a

brachial valve of Tropidoleptus sp., Weltevrede Formation, Howison’s Poort. x 4. D. External

mould of a brachial valve of Tropidoleptus sp., Wagen Drift Formation, Avondrus, south-east of

Touws River. X 5. E. External mould of a pedicle valve of Lingula sp., Wagen Drift

Formation, Elim, west of Touws River. X 2,5.

224 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 8. Fossils from the Weltevrede Formation, Howison’s Poort. A. Trilobite, Trimerus? sp.

x 4. B. Bivalve, Palaeoneilo sp. Xx 2. C. Gastropod, Plectonotus sp. Xx 4. D. Bivalve

Modiomorpha? sp. Xx 3,5. E. Gastropod, Plectonotus sp. Xx 4. F. Bivalve, Sanguinolites sp.

x 2,5. All specimens are preserved as internal moulds.

SEDIMENTARY FACIES IN THE LOWER WITTEBERG GROUP OES)

Tropidoleptus sp. A specimen in the British Museum (Natural History) has been

identified as aff. Trigonoglossa but again nothing in the author’s collection

corresponds to such an assignment. The generic placement of the trilobite remains

in some doubt but workers at the British Museum (Natural History) believe that

it might be a species of Trimerus (pers. comm. 1986). Among the bivalves the

following genera are tentatively recorded: Palaeoneilo sp., Nuculites sp., San-

guinolites sp., Paraprothyris sp., Janeia sp., and Modiomorpha sp. The collec-

tion is thus dominated by bivalves. The single gastropod is a species of

Plectonotus.

PALAEOECOLOGY

Brachiopods are epifaunal suspension feeders that are restricted to more

or less normal marine conditions. The only known exception to this general

rule is Lingula, which is an infaunal suspension feeder known to be moderately

euryhaline and capable of withstanding reduced salinities for short periods.

Hammond (1983) showed that a living species of Lingula may tolerate salinity

levels down to 16%c and up to 50%c for prolonged periods, and exposure to

levels as low as 5%o for shorter periods. At the present time the genus lives in

nearshore habitats, including estuaries and intertidal flats, often in brackish

water, and there is a wealth of evidence to suggest that throughout its

stratigraphic range (at least back to the Ordovician), it occurred in nearshore

faunas that were characterized by low species diversity usually with no more

than five taxa (Raup & Stanley 1971: 208). It seems reasonable to suggest,

therefore, that abundant Lingula in the Witteberg Group represents a

nearshore setting, possibly with fluctuating salinity. However, the greater

diversity of brachiopods in the Touws River localities would indicate less

stressful salinity conditions. Orbiculoidea may have been planktonic or, more

likely, epiplanktonic—attaching to algal fronds that are not preserved. Such a

life-style would mean that it could turn up in almost any shallow marine habitat

but the association of orbiculoid and linguloid brachiopods is a common one in

many Silurian and Devonian rocks of nearshore origin (Boucot 1975).

Palaeozoic bivalves were largely non-siphonate and most were shallow

infaunal deposit feeders or semi-infaunal suspension feeders (Stanley 1968). In

Silurian and Devonian rocks they are commonly associated with Lingula in

shallow nearshore habitats, although they did range into deeper shelf waters

(Copper 1977).

Another common association in Silurian and Devonian rocks is that of

homalonotid trilobites with the snail '/ectonotus, and Boucot (1975) has

documented this association from many parts of the world. It is not certain what

sort of life habits were adopted by these creatures but the shape of the cephalon

on the trilobites suggests they may have foraged for food by ploughing through

the upper centimetre or so of sediment. The gastropods may have been herbi-

vores. Homalonotids are known to occur in deeper-water environments, but the

226 ANNALS OF THE SOUTH AFRICAN MUSEUM

association with Plectonotus always seems to occur in a shallow nearshore setting

(Boucot 1975).

Associations of this sort just described were termed communities by Boucot

(1975), who defined a community as a recurring association of taxa that require

the same range of environmental conditions or that are dependent on one

another. Using a number of such Palaeozoic communities, based largely on

brachiopods, he recognized six benthic assemblages representing increasing dis-

tance from the shoreline. This, in turn, could be broadly correlated with

increasing depth and decreasing temperature. Each benthic assemblage was made

up of one or more co-existing communities.

Benthic assemblages 1 and 2 are interpreted as representing the high

and low intertidal zones respectively (Boucot 1975); benthic assemblages

3, 4 and 5 represent increasingly deep subtidal areas on the continental shelf,

and benthic assemblage 6 represents deeper water beyond the local shelf edge.

For the Malvinokaffric Realm (a Silurian—Devonian palaeogeographic and

biogeographic realm that included South Africa, the Falkland Islands and

South America south of about 10° S), Boucot (1975: 18) showed that benthic

assemblage 1 contains three low-diversity communities—a homalonotid—

Plectonotus community, an orbiculoid—linguloid community and an infaunal

bivalve community. Benthic assemblage 2 contains a number of low-

diversity brachiopod communities including a Tropidoleptus community.

Benthic assemblage 3 contains a _ high-diversity chonetid community,

and a _ high-diversity spiriferid community stretches across _ benthic

assemblages 4 and 5. The trace fossil Zoophycos is said to range through

benthic assemblages 3-5. Figure 9 provides a summary of this scheme.

A certain amount of community mixing may occur at assemblage boun-

daries.

The low diversity communities, such as are found in benthic assemblages 1

and 2, can be explained by the restrictive conditions of the intertidal environment

with its wide fluctuations in temperature, salinity and exposure to the atmosphere.

The more stable infaunal environment permits a somewhat more diverse bivalve

fauna to be present. The taxa that dominate the low-diversity communities of

benthic assemblages 1 and 2 may also be found in high-diversity communities in

deeper-water subtidal conditions (Boucot et al. 1983).

The collection of fossils from the Howison’s Poort locality clearly relate to

benthic assemblages 1 and 2 of Boucot’s scheme, and can readily be assigned

to the four communities making up those assemblages. This would suggest that

the fossils represent an intertidal environment. Figure 10 is a cartoon

reconstruction of the environment envisaged for the Howison’s Poort site. In

contrast, the brachiopod fauna from the Western Cape localities would

indicate the deeper-water subtidal conditions of benthic assemblages 3 and 4,

although the number of Lingula specimens recovered from the top of the

Wagen Drift Formation might suggest a progressive shallowing of the

environment.

SEDIMENTARY FACIES IN THE LOWER WITTEBERG GROUP 27,

strand line

A “intertidal

subtidal zone

BA = Benthic Assemblage

Fig. 9. Schematic representation of the communities and benthic assemblages recognized in the

Witteberg Group, showing their relationship to depth and distance from the shore line.

(After Boucot 1975.)

SS cal MS : ‘ a7

: ee ge 26

SP 6, LS AE & BR

i H sis ie 2 Maer : EILO

X ee -

\ ~ a

A NH ‘

Se (

PARAPROTHYRIS

SANGUINOLITES

Fig. 10. Cartoon reconstruction of the intertidal communities of the Weltevrede Formation in

Howison’s Poort.

228 ANNALS OF THE SOUTH AFRICAN MUSEUM

AGE

The general lack of fossils in the Witteberg Group has made dating of the

rocks rather difficult. Fish remains from the Waaipoort Formation in the upper

part of the group led Gardiner (1969) to propose a Lower Carboniferous age,

whereas Stapleton (1977a, 1977b) used spores from the same horizon to deter-

mine a Middle or Upper Devonian (Givetian—Frasnian) age. Witteberg plant

macrofossils suggested a late Devonian age to Plumstead (1967, 1969). Boucot et

al. (1983) discussed these various age determinations and used the presence of the

brachiopod Tropidoleptus, a genus that apparently does not occur in similar facies

in the underlying Bokkeveld Group, to suggest a Givetian or Frasnian age for the

lower part of the Witteberg Group.

Such an age determination agrees well with the suggestion of Cooper (1982,

1986), who used eustatic sea-level changes to effect a correlation with Devonian

rocks in Europe and North America. His proposals gave a Givetian age for the

Wagen Drift Formation and a Frasnian age for the top part of the Weltevrede

Formation. This slight age difference is unimportant in explaining the differences

in the fauna between the localities described here. As has been pointed out, many

of the forms recovered from these localities are quite long ranging and are found

in the Bokkeveld Group. Environmental differences are the important factors in

determining the faunal differences.

CONCLUSIONS

Rare Middle to Upper Devonian marine invertebrates from a few

widespread localities in the lower part of the Witteberg Group represent a

number of benthic communities similar to those recorded from other parts of

the world. The locality at Howison’s Poort in the Eastern Cape has yielded an

intertidal assemblage dominated by infaunal bivalves but also containing

orbiculoid and linguloid inarticulate brachiopods, Tropidoleptus (an articulate

brachiopod), a homalonotid trilobite and the gastropod Plectonotus. In

contrast to this, two localities in the Wagen Drift Formation near Touws River

have yielded a deeper-water subtidal assemblage dominated by articulate

brachiopods, including Australospirifer, Chonetes and Tropidoleptus. Increas-

ing numbers of the inarticulate Lingula near the top of the formation may

indicate shallowing of the water.

The different interpretations of the faunal assemblages from the two areas

accord well with the different interpretations of the containing sedimentary facies.

The shales at the top of the Weltevrede Formation at Howison’s Poort are

thought to have been deposited in intertidal flats established during transgressive

reworking of an abandoned delta lobe. The Wagen Drift Formation is taken to

represent a prograding delta and its shales were deposited in a delta slope

environment.

SEDIMENTARY FACIES IN THE LOWER WITTEBERG GROUP 229

REFERENCES

Boucot, A. J. 1975. Evolution and extinction rate controls. Amsterdam: Elsevier.

Boucot, A. J., BRUNTON, C. H. C. & THERON, J. N. 1983. Implications for the age of South

African Devonian rocks in which Tropidoleptus (Brachiopoda) has been found. Geological

Magazine 120 (1): 51-58.

Cooper, M. R. 1982. A revision of the Devonian (Emsian—Eifelian) Trilobita from the

Bokkeveld Group of South Africa. Annals of the South African Museum 89 (1): 1-174.

Cooper, M. R. 1986. Facies shifts, sea-level changes and event stratigraphy in the Devonian of

South Africa. South African Journal of Science 82 (5): 255-258.

Copper, P. 1977. Paleolatitudes in the Devonian of Brazil and the Frasnian—Famennian mass

extinction. Palaeogeography, Palaeoclimatology, Palaeo-ecology 21: (3): 165-207.

E.uiot, T. 1974. Interdistributary bay sequences and their genesis. Sedimentology 21: 611-622.

FISHER, W. L., Brown, L. F., Scotr, A. J. & McGowen, J. H. 1969. Delta systems in the

exploration for oil and gas. Austin, Texas: Bureau of Economic Geology, University of

Texas at Austin.

GARDINER, B. G. 1969. New palaeoniscoid fish from the Witteberg Series of South Africa.

Zoological Journal of the Linnaean Society of London 48 (4): 423-452.

HAMMOND, L. S. 1983. Experimental studies of salinity tolerance, burrowing behaviour and

pedicle regeneration in Lingula anatina (Brachiopoda, Inarticulata). Journal of Paleont-

ology 57 (6): 1311-1316.

HILLeR, N. & DUNLEVEY, J. N. 1978. The Bokkeveld—Witteberg boundary in the Montagu-—

Touws River area, Cape Province. Transactions and Proceedings of the Geological Society

of South Africa 81 (1): 101-104.

HusBArpD, D. K. & Barwis, J. H. 1976. Discussion of tidal inlet sand deposits: examples from

the South Carolina coast, IID. In: Hayes, M. O. & Kana, T. W. Terrigenous clastic

depositional environments. Technical Report. University of South Carolina 11—CRD:

128-142.

JOHNSON, M.R. 1976. Stratigraphy and sedimentology of the Cape and Karoo sequences in the

eastern Cape Province. Rhodes University: Unpublished Ph.D thesis.

Juss. R. A. 1965. A new paleoniscid fish from the Witteberg Series (Lower Carboniferous) of

South Africa. Annals of the South African Museum 48 (15): 267-272.

Kumar, N & SANDERS, J. E. Inlet sequence: a vertical succession of sedimentary structures

created by lateral migration of tidal inlets. Sedimentology 21 (2): 291-323.

Loock, J. C. 1967. The stratigraphy of the Witteberg—-Dwyka contact beds. University of

Stellenbosch: Unpublished M.Sc. thesis.

PICKERILL, R. K. & Hurst, J. M. 1983. Sedimentary facies, depositional environments, and

faunal associations of the lower Llandovery (Silurian) Beechill Cove Formation, Arisaig,

Nova Scotia. Canadian Journal of Earth Sciences 20 (12): 1761-1779.

PLUMSTEAD, E. P. 1967. A general review of the Devonian fossil plates found in the Cape

System of South Africa. Palaeontologia africana 10: 1-83.

PLUMSTEAD, E. P. 1969. Three thousand million years of plant life in Africa. Transactions and

Proceedings of the Geological Society of South Africa.72 (Annexure).

Raup, D. M. & STANLEY, S. M. 1971. Principles of palaeontology. San Francisco: W. H.

Freeman & Co.

REDDERING, J. S. V. 1983. An inlet sequence produced by migration of a small microtidal inlet

against longshore drift: the Keurbooms Inlet, South Africa. Sedimentology 30 (2): 201-218.

REED, F. R. C. 1925. Revision of the fauna of the Bokkeveld Beds. Annals of the South African

Museum 22 (1): 27-225.

Reinson, G. E. Barrier island and associated strand-plain systems. Jn: WALKER, R. G. Facies

models: 119-140. 2nd ed. Toronto: Geological Association of Canada.

SouTH AFRICAN COMMITTEE FOR STRATIGRAPHY. 1980. Stratigraphy of South Africa. Part 1.

Lithostratigraphy of the Republic of South Africa, South West Africa/Namibia, and the

Republics of Bophuthatswana, Transkei and Venda. Handbook. Geological Survey of

South Africa, Republic of South Africa 8: 1-690.

STANLEY, S. M. 1968. Post-Paleozoic adaptive radiation of infaunal bivalve molluscs—

consequence of mantle fusion and siphon formation. Journal of Paleontology 42 (1):

214-229.

230 ANNALS OF THE SOUTH AFRICAN MUSEUM

STAPLETON, R. P. 1977a. Carboniferous unconformity in southern Africa. Nature, London 268

(5617): 222-223.

STAPLETON, R. P. 1977b. Carbonised Devonian spores from South Africa. Pollen et spores 19:

427-440.

Swart, B. 1950. Morphological aspects of the Bokkeveld Series at Wuppertal, Cape Province.

Annale van die Universiteit van Stellenbosch (A) 26 (10): 413-479.

TANKARD, A. J. & BARwis, J. H. 1982. Wave-dominated deltaic sedimentation in the Devonian

Bokkeveld basin of South Africa. Journal of Sedimentary Petrology 52 (3): 959-974.

TANKARD, A. J., Jackson, M. P. A., Ertksson, K. A., Hospay, D. K., Hunter, D. R. &

Minter, W. E. L. 1982. Crustal evolution of southern Africa. 3.8 billion years of earth

history. New York: Springer-Verlag.

THERON, J. N. 1962. An analysis of the Cape folding in the district of Willowmore, Cape

Province. Annale van die Universiteit van Stellenbosch (A) 37 (5): 247-419.

THERON, J. N. 1970. A stratigraphical study of the Bokkeveld Group (Series). In: Second

Gondwana Symposium. Proceedings and papers: 197-204. Pretoria: Council for Scientific

and Industrial Research.

THERON, J. N. 1972. The stratigraphy and sedementation of the Bokkeveld Group. University

of Stellenbosch: Unpublished D.Sc. thesis.

WriGuT, L. D. 1978. River deltas. In: Davis, R. A. Coastal sedimentary environments: 5-68.

New York: Springer-Verlag.

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Family Nuculanidae

Nuculana (Lembulus) bicuspidata (Gould, 1845)

Figs 14-15A

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Leda plicifera A. Adams, 1856: 50.

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NORTON HILLER

BENTHIC COMMUNITIES AND

SEDIMENTARY FACIES IN THE LOWER

WITTEBERG GROUP

(DEVONIAN, SOUTH AFRICA)

i ,

Js, VOLUME 99 PART 8 JULY 1990 ISSN 0303-2515

ANNALS.

OF THE SOUTH AFRICAN

~~ MUSEUM

CAPE TOWN

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last pages of article).

Examples (note capitalization and punctuation)

BuLLouGu, W. S. 1960. Practical invertebrate anatomy. 2nd ed. London: Macmillan.

FiscHER, P. H. 1948. Données sur la résistance et de la vitalité des mollusques. Journal de conchyliologie 88 (3): 100-140.

FiscHErR, P. H., DuvAL, M. & Rarry, A. 1933. Etudes sur les échanges respiratoires des littorines. Archives de zoologie

expérimentale et générale 74 (33): 627-634.

Koun, A. J. 1960a. Ecological notes on Conus (Mollusca: Gastropoda) in the Trincomalee region of Ceylon. Annals and

Magazine of Natural History (13) 2 (17): 309-320.

Koun, A. J. 1960b. Spawning behaviour, egg masses and larval development in Conus from the Indian Ocean. Bulletin of

the Bingham Oceanographic Collection, Yale University 17 (4): 1-51.

THIELE, J. 1910. Mollusca. B. Polyplacophora, Gastropoda marina, Bivalvia. In: ScHULTzE, L. Zoologische und anthro-

pologische Ergebnisse einer Forschungsreise im westlichen und zentralen Stid-Afrika ausgefiihrt in den Jahren

1903-1905 4 (15). Denkschriften der medizinisch-naturwissenschaftlichen Gesellschaft zu Jena 16: 269-270.

(continued inside back cover)

ANNALS OF THE SOUTH AFRICAN MUSEUM

ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM

Volume 99 Band

July 1990 Julie

Part 8 Deel

CRETACEOUS FAUNAS FROM ZULULAND

AND NATAL, SOUTH AFRICA

HATCHERICERAS STANTON, 1901

(CEPHALOPODA, AMMONOIDEA),

FROM THE BARREMIAN OF ZULULAND

WILLIAM JAMES KENNEDY

HERBERT CHRISTIAN KLINGER

Cape Town Kaapstad

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are issued in parts at irregular intervals as material

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C648

CRETACEOUS FAUNAS FROM ZULULAND

AND NATAL, SOUTH AFRICA.

HATCHERICERAS STANTON, 1901

(CEPHALOPODA, AMMONOIDEA),

FROM THE BARREMIAN OF ZULULAND

WILLIAM JAMES KENNEDY

Geological Collections, University Museum, Oxford

HERBERT CHRISTIAN KLINGER

Department of Invertebrate Palaeontology, South African Museum, Cape Town

(With 6 figures)

[MS accepted 27 October 1989]

ABSTRACT

Hatchericeras patagonense Stanton, 1901, previously known only from the Austral Basin of

Argentina, is described from the Barremian of northern Zululand. All but one described

species of Hatchericeras, and of Pseudohatchericeras Leanza, 1970, are placed in synonymy.

CONTENTS

PAGE

AEROCIUC HON earn etn rere terest ene nM RE Sha Be ee MIE 231

PocaviOMOMmSMeCMMe Serer ee er a ea eames A Ge 5 anes 7138)

DIMENSIONS OLSPECIMENSMe amie Goh oe een ee ce hina here ee ee Sie 233

SUMUNCHLEHIMINOLO LY eee cer pete eis cee ag AON Grd eis ec GS ales no es 233

Systematicipalacontology oa 2- ase erie e ca ose lan mas ee eb eielon M33)

PNCKMOWLEUGEIMCI (Sera we ns eee oe es nA Bae aoe adece 4 votes Sensis 241

IRGEMOMNCOS SG, gio bd BONO i cda ed asec GPO ERA Ce CFO OTC ek eae ee 242

INTRODUCTION

The genus Hatchericeras was introduced by Stanton (1901) for a series of

ammonites collected by J. B. Hatcher during the Princeton University expedi-

tions to Patagonia (1896-1899) (see Hatcher 1900) near the mouth of the canyon

of the Rio Tarde, from what were termed the Belgrano beds, and from essen-

tially the same horizon some 16,5 km (10 miles) east of Lake Pueyrredon, in

Patagonia. Stanton dated the fauna as ‘not later than the Gault’ (p. 10), that is

to say Albian or older, describing Hatchericeras patagonense, the type species,

based on three specimens (1901: 38, pl. 8 (figs 1-2), pl. 9 (fig. 1); H. argentin

ense (1901: 39, pl. 9 (figs 2-5)), based on at least four specimens; H.? tardense

Ann. S. Afr. Mus. 99 (8), 1990: 231-243, 6 figs.

232 ANNALS OF THE SOUTH AFRICAN MUSEUM

(1901: 41, pl. 10 (figs 3-5S)), based on one specimen; and H.? pueyrrydonense

(1901: 42, pl. 10 (figs 1-2)), based again on one specimen only. Stanton was

uncertain of the affinities of his new genus, but concluded it was closest to the

Hoplitidae (1901: 38). Favre (1908: 631, pl. 35 (figs 3-4), text-fig. 5) introduced

a further species, H. stantoniense, from the Cerro Belgrano, Patagonia, based

on a solitary specimen, without commenting on its taxonomic position. Spath

(1923: 307) thought Hatchericeras might be matched with his new genus Proleo-

poldia, subsequently referred to the subfamily Garniericeratinae of the Cras-

peditidae (Perisphinctaceae) with a query by Wright (1957: L344). Roman

(1938: 343) referred Hatchericeras to the Hauterivian and placed it in the sub-

family Neocomitinae of the Perisphinctaceae, a view followed by Wright (1957:

L360) and Woods (1962: 240). Leanza (1970: 233) believed Hatchericeras was of

Albian date, and placed it in the subfamily Gastroplitinae (Hoplitaceae),

describing specimens of H. patagonense, H. santacrucense Leanza, 1970 (p. 237,

fig. 32 (1, 2)), H. semilaeve Leanza, 1970 (p. 237, figs 33 (1-4), 34 (1, 2), 35

(1, 3), 36 (1), 37 C, 2)) and A. hatcheri Leanza, 1970 (p. 242, fig. 38 (1=3));

and introducing the genus Pseudohatchericeras with H. argentinense Stanton,

1901, as type species. All appear to come from the same general level in the Rio

Belgrano Formation, albeit from different localities, according to Leanza.

As Riccardi & Aguirre Urreta (1989: 447) noted, the seeming endemism

of Hatchericeras and other elements of the Patagonian fauna led to the view

that rocks of Valanginian—Barremian age were absent (e.g. Leanza 1963)

in the Austral Basin. Subsequently, Riccardi (1984a, 1984b, 1988) and Riccardi

& Aguirre Urreta (1989) recognized a Hauterivian to Barremian zonal

sequence of:

B : Colchidites Zone

ae Gear Hatchericeras patagonense Zone

SD Favrella wilckensi Zone

Hauterivian :

Favrella americana Zone

Hatchericeras species are listed only from the H. patagonense Zone, which

also yields Cryptocrioceras yrigoyeni (Leanza, 1970), Hemihoplites varicostatus

Riccardi & Aguirre Urreta, 1989, and Sanmartinoceras africanum insignicosta-

tum Riccardi et al., 1987. The Colchidites Zone yields Colchidites vulanensis

Egoian, 1965 australis Klinger, Kakabadze & Kennedy, 1984, Heteroceras elegans

Rouchadzé, 1933, and S. africanum insignicostatum.

All of these species occur in Zululand, where Sanmartinoceras africanum

Kennedy & Klinger, 1979, is represented by the nominate subspecies rather than

S. africanum insignicostatum; aconeceratids are described by Kennedy &

Klinger (1979); heteroceratids by Klinger (1976), Klinger et al. (1984) and

Aguirre Urreta & Klinger (1986); Hatchericeras herein; and the remaining

heteromorphs in a forthcoming publication (Klinger & Kennedy in prep.). The

H. patagonense Zone corresponds to division Barremian I of Kennedy &

CRETACEOUS FAUNAS FROM ZULULAND AND NATAL 235

Klinger (1975: 274), and the Colchidites Zone to division Barremian II of these

authors. :

The Hatchericeras described below are amongst the oldest ammonites

known from Zululand, first appearing in bed 4 at locality 170 on Mlambo-

ngwenya Spruit (Kennedy & Klinger 1975, fig. 11; Aguirre Urreta & Klinger

1986, fig. 3).

LOCATION OF SPECIMENS

The following abbreviations are used to indicate the repositories of the

material studied:

OUM Oxford University Museum, Oxford.

PU ___s‘ Princeton University Collections, Princeton.

SAM South African Museum, Cape Town.

DIMENSIONS OF SPECIMENS

All dimensions given below are in millimetres: D = diameter, Wb = whorl

breadth, Wh = whorl height, U = umbilical diameter.

Figures in parentheses are dimensions as a percentage of the total diameter.

SUTURE TERMINOLOGY

The suture terminology of Wedekind (1916), as reviewed by Kullman &

Wiedmann (1970) is followed here: E = external lobe, L = lateral lobe,

U = umbilical lobe, I = internal lobe.

SYSTEMATIC PALAEONTOLOGY

Phylum MOLLUSCA

Class CEPHALOPODA

Order AMMONOIDEA Zittel, 1884

Suborder AMMONITINA Zittel, 1884

Superfamily PERISPHINCTACEAE Steinmann, 1890

Family Neocomitidae Salfeld, 1921

Subfamily Neocomitinae Salfeld, 1921

Genus Hatchericeras Stanton, 1901

[= Pseudohatchericeras Leanza, 1970]

Type species. Hatchericeras patagonense Stanton, 1901 (p. 38, pl. 8

(figs 1-2), pl. 9 (fig. 1), by original designation by Stanton (1901: 35).

Discussion

Pseudohatchericeras Leanza, 1970 (p. 244), with Hatchericeras argentinense

Stanton, 1901 (p. 39, pl. 9 (figs 2-5) as type species, seems to be no more than a

234 ANNALS OF THE SOUTH AFRICAN MUSEUM

flat-ribbed Hatchericeras (e.g. compare Riccardi 1988, pl. 10 (figs 1-2) and

pl. 10 (figs 3-4)), and is regarded as a synonym. Recognition that Hatchericeras

is Barremian indicates that it is unlikely to be a member of the Albian—Lower

Cenomanian Gastroplitinae as proposed by Leanza (1970), whereas the strong

similarities of ornament and suture line link it to the Neocomitinae, as proposed

by Roman (1938) and Wright (1957). The resemblance of Hatchericeras and

Alopecoceras Kennedy & Klinger, 1978 (type species Alopecoceras ankeritterae

Kennedy & Klinger, 1978: 60, figs 1-4, 5A-B, 6, 7E-G), from the Middle

Albian of Zululand, as suggested by Kennedy & Klinger (1978), is thus revealed

as homeomorphous. The origin of Alopecoceras is possibly in the “Cleoniceras’-

like forms described from the Albian of Madagascar by Collignon (1963).

Occurrence

Barremian of the Austral Basin, southern Patagonia, and northern Zulu-

land. Woods (1962) recorded Hatchericeras lakefieldense from the Laura Basin

of Queensland, Australia, and regarded it as Lower Hauterivian, on the basis of

the presumed Hauterivian age of the Patagonian examples of Hatchericeras.

Hatchericeras patagonense Stanton, 1901

Figs 1-6

Hatchericeras patagonense Stanton, 1901: 38, pl. 8 (figs 1-2), pl. 9 (fig. 1). Roman, 1938: 343,

fig. 34, 323. Wright, 1957: L361, fig. 470 (1). Leanza, 1970: 234, fig. 30 (1-4), fig. 31a

(1, 3), fig. 31b (2). Riccardi, 1988, pl. 9 (figs 7-8).

Hatchericeras argentinense Stanton, 1901: 39, pl. 9 (figs 2-5).

Hatchericeras? tardense Stanton, 1901: 41, pl. 10 (figs 3-5). Riccardi, 1988, pl. 10 (figs 6-7).

Hatchericeras? pueyrrydonense Stanton, 1901: 42, pl. 10 (figs 1-2). Riccardi, 1988, pl. 10

(figs 3-4).

Hatchericeras stantoniense Stant. n. sp. Favre, 1908: 631, pl. 35 (figs 3-4), text-fig. 5.

Hatchericeras cf. pueyrrydonense Stant. Favre, 1908: 632.

Hatchericeras santacrucense Leanza, 1970: 237, fig. 32 (1-2).

Hatchericeras semilaeve Leanza, 1970: 237, fig. 33 (1-4), fig. 34 (1-2), fig. 35 (1-3), fig. 36 (1),

fig. 37 (1-2). Kennedy & Klinger, 1978, figs 6C, 7A—D.

Hatchericeras hatcheri Leanza, 1970: 242, fig. 38 (1-3).

Pseudohatchericeras argentinense (Stanton) Leanza, 1970: 244, fig. 39 (1-3). Riccardi, 1988,

pl. 10 (figs 1-2).

Type

Holotype is PU 66, the original of Stanton (1901, pl. 8 (figs 1-2), pl. 9

(fig. 1)), refigured by Riccardi (1988, pl. 9 (figs 7-8)), from Lago Pueyrredon,

Santa Cruz Province, Argentina.

Material

OUM KX 1804 and 1819, from bed 3 at locality 170 of Kennedy & Klinger

(1975), and OUM KX 1820-1821, from a slightly higher horizon, Makatini For-

mation, Mlambongwenya Spruit, Zululand. Barremian I.

CRETACEOUS FAUNAS FROM ZULULAND AND NATAL

Fig. 1. Hatchericeras patagonense Stanton, 1901. A-C. OUM KX 1820.

D-F. OUM KX 1819. G. OUM KX 1804. A-F x 1, G x 0,6.

3 )5)

236

ANNALS OF THE SOUTH AFRICAN MUSEUM

Dimensions

Specimen D Wb Wh Wb/Wh U

Holotype 11 PU 66 250 (100) 72 (28,8) 148 (59,2) 0,49 33) (212)

Paratype 1! 210 (100) 3) (COO) 113 (3,8) O55 45 (21,4)

Paratype 2! 300 (100) 94 (31,3) 175 (58,3) 0,54 62 (20,7)

OUM KX 1804 250 (100) = 72 (28,8) 123 (49,2) 0,58 31 (12,4)

OUM KX 1819 51 (—) 86 (—) 0,59

! from Stanton (1901)

Description

OUM KX 1820 and 1821 (Fig. [A-F) are fragments of small body

chambers of specimens that were an estimated 50-60 mm in diameter. Coiling is

involute, with a small, shallow umbilicus. The umbilical wall is flattened and

outward-inclined, giving rise to a conical circumumbilical pit. The whorl sections

are compressed, with broadly rounded inner flanks, flattened, convergent outer

flanks and a somewhat flattened venter in intercostal section, with the greatest

breadth just outside the umbilical shoulder. Strong, distant, narrow ribs are

straight and prorsiradiate on the inner flank. They flex back and thicken across

the mid-flank, where they are convex, flex forwards and are concave on the

outer flank, and strengthen into blunt incipient ventrolateral bullae. The ribs

weaken somewhat on the venter, where they are broad and transverse. Two ribs

intercalate between the primaries, arising either low on the flank or at mid-

flank, strengthening to match the primary ribs on outer flank and venter. The

dorsum of OUM KX 1820 shows details of the ornament at an even smaller

diameter; the ribs are more crowded than in the somewhat larger whorls.

OUM KX 1819 (Figs 3B, 4) is part of an adult phragmocone and the begin-

ning of the body chamber, with a maximum preserved whorl height of 100 mm.

Ornament is greatly reduced, with low, broad prorsiradiate ribs (Fig. 4) on the

flank, narrowing somewhat towards the umbilicus. The venter is broad, flat and

smooth (Fig. 3B). OUM KX 1804 (Figs 1G, 2) is a complete adult, 250 mm in

diameter. Ornament on the body chamber is reduced to irregular low ribs and

folds on the internal mould; where replaced shell survives, it is covered by deli-

cate prorsiradiate growth lines and striae. The venter is flattened throughout,

and broadens towards the adult aperture.

Suture (Fig. 6) with large, asymmetrically subtrifid E/L, broad trifid L,

smaller, subtrifid L/U2 and U2.

Discussion

The largest South African specimen differs in no significant respect from the

holotype of H. patagonense, illustrated photographically by Riccardi (1988, pl. 9

(figs 7-8)) or the Argentinian specimen shown in Figures 3A and 5, whereas the

type series of H. semilaeve Leanza, 1970 (p. 237, fig. 33 (1-4), fig. 34 (1-2),

fig. 35 (1-3), fig. 36 (1), fig. 37 (1-2)), link these feebly ornamented adults to

CRETACEOUS FAUNAS FROM ZULULAND AND NATAL

Fig. 2. Hatchericeras patagonense Stanton, 1901. OUM KX 1804. x 0,6.

238 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 3. Hatchericeras patagonense Stanton, 1901. A. SAM-—PC8454, from Chorrillo Rivero-

Rio Roble, Argentina. B. OUM KX 1819. All x 1.

239

CRETACEOUS FAUNAS FROM ZULULAND AND NATAL

Fig. 4. Hatchericeras patagonense Stanton, 1901. OUM KX 1819. x 1.

240 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 5. Hatchericeras patagonense Stanton, 1901. SAM-—PC8454, from. Chole Rivero-Rio

Roble, Argentina. Specimen kindly donated by M. B. Aguirre Urreta, Buenos Aires. x 1.

CRETACEOUS FAUNAS FROM ZULULAND AND NATAL 241

10mm

Fig. 6. Hatchericeras patagonense Stanton, 1901. OUM KX 1819. Suture line.

Scale = 10 mm.

the small specimens illustrated here as Figure 1A—F. The other species

described by Stanton (1901), Favre (1908), and Leanza (1970), from a limited

stratigraphical interval only, in the authors’ view, illustrate no more than the

normal range of variation in juvenile ammonites, and are regarded as con-

specific. Hatchericeras lakefieldense Woods, 1962, is difficult to interpret. It

looks like a representative of Hatchericeras, but seems more evolute, with a

wider umbilicus than the type species, H. patagonense, when adult.

Occurrence

Barremian, Hatchericeras patagonense Zone of the Austral Basin, Argen-

tina, and Makatini Formation, Barremian I, Locality 170, Mlambongwenya

Spruit, Zululand.

ACKNOWLEDGEMENTS

Kennedy acknowledges the financial support of the Natural Environment

Research Council (UK) and Royal Society (UK), and the technical assistance of

the staff of the Geological Collections, Oxford University Museum, and Depart-

ment of Earth Sciences, Oxford. Klinger acknowledges the support of the

Foundation for Research Development and the South African Museum, and the

technical assistance of Mss S. Dove, J. Blaeske and M. Joubert (South African

Museum). We both thank Dr M. B. Aguirre Urreta (Buenos Aires) for mean-

ingful discussions while preparing the manuscript and for donating the

Patagonian specimen of H. patagonense figured in Figures 3A and 5 to the South

African Museum.

242 ANNALS OF THE SOUTH AFRICAN MUSEUM

REFERENCES

AGUIRRE UrreTA, M. B. & KLINGER, H. C. 1986. Upper Barremian Heteroceratinae (Cephalo-

poda, Ammonoidea) from Patagonia and Zululand, with comments on the systematics of

the subfamily. Annals of the South African Museum 96 (8): 315-358.

CoLLIGNoN, M. 1963. Atlas des fossiles caractéristiques de Madagascar (Ammonites). X.

(Albien). Tananarive: Service Géologique

Ecoran, V. L. 1965. [On the first find of colchiditids in north-western Caucasus.] Trudy

Vsesoyuznogo Nettyanogo Nauchno-Issledovatel’skogo Geologischeskogo-Razvedochnogo

Institut 44: 116-127. (In Russian.)

Favre, F. 1908. Die Ammoniten der Unteren Kreide Patagoniens. Neues Jahrbuch ftir Minera-

logie, Geologie und Paldontologie 25: 601-647.

Hatcu_er, J. B. 1900. Sedimentary rocks of southern Patagonia. American Journal of Science

(4) 9 (50): 85-108.

KENNEDY, W. J. & KLINGER, H. C. 1975. Cretaceous faunas from Zululand and Natal, South

Africa. Introduction, stratigraphy. Bulletin of the British Museum (Natural History)

(Geology) 25 (4): 263-315.

KENNEDY, W. J. & KLINGER, H. C. 1978. Cretaceous faunas from Zululand and Natal, South

Africa. A new genus and species of Gastroplitinae from the Mzinene Formation (Albian).

Annals of the South African Museum 77 (4): 57-69.

KENNEDY, W. J. & KLINGER, H. C. 1979. Cretaceous faunas from Zululand and Natal, South

Africa. The ammonite superfamily Haplocerataceae Zittel, 1884. Annals of the South

African Museum 77 (6): 85-121.

KLINGER, H. C. 1976. Cretaceous heteromorph ammonites from Zululand. Memoir of the

Geological Survey of South Africa 69: 1-142.

KLINGER, H. C., KAKABADZE, M. V. & KENNEDY, W. J. 1984. Upper Barremian (Cretaceous)

heteroceratid ammonites from South Africa and Caucasus and their palaeobiogeographic

significance. Journal of Molluscan Studies 50 (1): 43-60.

KULLMAN, J. & WIEDMANN, J. 1970. Significance of sutures in phylogeny of Ammonoidea.

Paleontological Contributions. University of Kansas 44: 1-32.

LEANZA, A. 1963. Patagoniceras gen. nov. (Binneyitidae) y.otros ammonites del Cretacico

superior de Chile Meridional con notas acera de su posiciOn estratigrafica. Boletin do Aca-

demia Nacional Ciencias, Cérdoba 43: 203-2235.

LEANZA, A. 1970. Ammonites nuevos 0 poco conocidos del Aptiano, Albiano y Cenomaniano

de los Andes Australes con notas acera de su posicion estratigrafica. Revista de la Asocia-

cion Geologica Argentina 25 (2): 197-261.

Riccarpi, A. C. 1984a. Las Asociaciones de Amonitas de Jurasico y Cretacico de la Argentina.

9 Congreso Geolédgico Argentino 4: 559-595.

Riccarpi, A. C. 1984b. Las zones de Amonitas de Cretacico de la Patagonia (Argentina y

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Riccarpi, A. C. 1988. The Cretaceous System of southern South America. Memoirs. Geolo-

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RiccArDI, A. C. & AGUIRRE URRETA, M. B. 1989. Hemihoplitid ammonoids from the Lower

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Riccarpi, A. C., AGUIRRE UrreETA, M. B. & MeEpiNA, F. A. 1987. Anoceratidae (Ammonitina)

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SALFELD, H. 1921. Kiel-und Furchenbildung auf der Schalenaussenseite der Ammonoideen in

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gie, Geologie und Paldontologie 11: 343-347.

SpATH, L. F. 1923. On ammonites from New Zealand. Quarterly Journal of the Geological

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STANTON, T. W. 1901. The marine Cretaceous invertebrates. Report of the Princeton Expedition

to Patagonia 4 (1): 1-43.

CRETACEOUS FAUNAS FROM ZULULAND AND NATAL 243

STEINMANN, G. 1890. Jn: STEINMANN, G. & DODERLEIN, Elemente der Paldontologie. Leipzig:

R. Oldenbourg.

WEDEKIND, R. 1916. Uber Lobus, Suturallobus und Inzision. Zentralblatt fiir Mineralogie,

Geologie und Paldontologie (for 1916) (B) 8: 185-195.

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WriGHT, C. W. 1957. Cephalopoda, Ammonoidea. Jn: Moore, R. C. ed. Treatise on inverte-

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ZITTEL, K. A. von. 1884. Handbuch der Palaeontologie. Abt. 1, 2 (Lief. 3) Cephalopoda:

329-522. Munich & Leipzig: R. Oldenbourg.

6. SYSTEMATIC papers must conform to the International code of zoological nomenclature (particu-

larly Articles 22 and 51).

Names of new taxa, combinations, synonyms, etc., when used for the first time, must be followed

by the appropriate Latin (not English) abbreviation, e.g. gen. nov., sp. nov., comb. nov., syn. nov.,

etc:

An author’s name when cited must follow the name of the taxon without intervening punctuation

and not be abbreviated; if the year is added, a comma must separate author’s name and year. The

author’s name (and date, if cited) must be placed in parentheses if a species or subspecies is trans-

ferred from its original genus. The name of a subsequent user of a scientific name must be separated

from the scientific name by a colon.

Synonymy arrangement should be according to chronology of names, i.e. all published scientific

names by which the species previously has been designated are listed in chronological order, with all

references to that name following in chronological order, e.g.:

Family Nuculanidae

Nuculana (Lembulus) bicuspidata (Gould, 1845)

Figs 14-15A

Nucula (Leda) bicuspidata Gould, 1845: 37.

Leda plicifera A. Adams, 1856: 50.

Laeda bicuspidata Hanley, 1859: 118, pl. 228 (fig. 73). Sowerby, 1871: pl. 2 (fig. 8a—b).

Nucula largillierti Philippi, 1861: 87.

Leda bicuspidata: Nicklés, 1950: 163, fig. 301; 1955: 110. Barnard, 1964: 234, figs 8-9.

Note punctuation in the above example:

comma separates author’s name and year

semicolon separates more than one reference by the same author

full stop separates references by different authors

figures of plates are enclosed in parentheses to distinguish them from text-figures

dash, not comma, separates consecutive numbers.

Synonymy arrangement according to chronology of bibliographic references, whereby the year is

placed in front of each entry, and the synonym repeated in full for each entry, is not acceptable.

In describing new species, one specimen must be designated as the holotype; other specimens

mentioned in the original description are to be designated paratypes; additional material not regarded

as paratypes should be listed separately. The complete data (registration number, depository, descrip-

tion of specimen, locality, collector, date) of the holotype and paratypes must be recorded, e.g.:

Holotype

SAM-—A13535 in the South African Museum, Cape Town. Adult female from mid-tide region, King’s Beach, Port Eliza-

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BuL.LouGu, W. S. 1960. Practical invertebrate anatomy. 2nd ed. London: Macmillan.

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FiscHEeR, P. H., Duvat, M. & Rarry, A. 1933. Etudes sur les échanges respiratoires des littorines. Archives de zoologie

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Koun, A. J. 1960a. Ecological notes on Conus (Mollusca: Gastropoda) in the Trincomalee region of Ceylon. Annals and

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Koun, A. J. 1960b. Spawning behaviour, egg masses and larval development in Conus from the Indian Ocean. Bulletin of

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THIELE, J. 1910. Mollusca. B. Polyplacophora, Gastropoda marina, Bivalvia. In: SCHULTZE, L. Zoologische und anthro-

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(continued inside back cover)

ANNALS OF THE SOUTH AFRICAN MUSEUM

ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM

Volume 99 Band

September 1990 September

alten oe IDeCel

DEEP-WATER QUATERNARY OSTRACODA

FROM THE CONTINENTAL MARGIN OFF

SOUTH-WESTERN AFRICA

(SE ATLANTIC OCEAN)

R. V. DINGLE A. R. LORD

I. D. BOOMER

Cape Town Kaapstad

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C773

DEEP-WATER QUATERNARY OSTRACODA FROM

THE CONTINENTAL MARGIN OFF

SOUTH-WESTERN AFRICA (SE ATLANTIC OCEAN)

R. V. DINGLE

South African Museum, P.O. Box 61, Cape Town

A. R. Lorp

Micropalaeontology Research Unit, University College London,

Gower Street, London, United Kingdom

I. D. BOOMER

Department of Environmental Sciences, University of East Anglia, Norwich,

United Kingdom |

(With 63 figures and 13 tables)

[MS accepted 2 May 1989]

ABSTRACT

Thirty-one species of benthic Ostracoda, representing 15 genera and two indeterminate

categories, are recorded from water depths greater than 900 m on the continental margin off

south-western Africa. Important faunal changes at certain depths allow the assemblages to be

grouped into Upper Bathyal, Lower Bathyal and Abyssal zones. The limits of these faunal

zones correlate with boundaries within and between the major water masses: the Neritic/Upper

Bathyal boundary lies at the bathyal thermocline, which coincides with the base of the salinity

minimum zone of the Antarctic Intermediate Water (AAIW) mass (c. 950 m); the Upper/

Lower Bathyal boundary lies at the AAIW/North Atlantic Deep Water (NADW) mass contact

(1 500 m); and the Lower Bathyal/Abyssal boundary lies at the top of the NADW core zone

(c. 2 000 m). These structural changes in the water column are accompanied by alterations in

physical and chemical properties, and we attempt to assess the effectiveness of these as barriers

that maintain the integrity of the faunal zones. The relationships are complex and vary greatly

from species to species. In addition, we find that, although the overall abundance of ostracods

on the adjacent continental shelf positively correlates with high mud content in the sediments,

this relationship does not hold for continental slope and rise area. Certain deep-water species,

however, do prefer fine-grained substrates. In comparison with ostracod faunas from similar

depths in other parts of the Atlantic Ocean, the populations off south-western Africa have

Lower Bathyal and Abyssal taxa at somewhat shallower levels.

One genus (Rugocythereis) and seven species are new: Krithe capensis, K. spatularis,

K. rex, K. peypouqueti, Cytheropteron cronini, Buntonia rosenfeldi, and Echinocythereis what-

leyi. Six species have previously been described: Rugocythereis horridus (Whatley & Coles,

1987), Cytherella serratula (Brady, 1880), Dutoitella suhmi (Brady, 1880), Abyssocythere austra-

lis Benson, 1971, Poseidonamicus major Benson, 1972, and Henryhowella melobesioides

(Brady, 1869). Fourteen species are left in open nomenclature.

245

Ann. S. Afr. Mus. 99 (9), 1990: 245-366, 63 figs.

246 ANNALS OF THE SOUTH AFRICAN MUSEUM

CONTENTS

PAGE

IntroductOns.c%..<) Aes 65.0 ee es 3 ee ee eee 246

Phystoeraphic: and oceanopraphic scttingsaee see see oe eee eee 250

MAK OMOMY! oie. f a scthyoield 5 orcle Dake D ete eats ae © eRe eee eee Dau

DISCUSSION 26 oo eyhld a ea eo oeeoe aeee Se eee 329

Depthrangesjandttaunalizones-e 245 cee oe eee eee eae 329

Sedimentary and oceanographic environments ..................... 341

Intra-oceanic relationships’ ~.3%5-5- 450 soca ee ee eee 355

Conclusions 5.2 20h eis Lagos oie See Oe On ar Eee ee eee 359

Acknowledgements | ...245,4:4 50 ¢2,co0% 2 Sank oe tm Saas oe ees sae 361

References). gaia ai ee es iS ae ee Be ee eee 361

INTRODUCTION

Until the advent of the Deep Sea Drilling Project, the main database on

deep-sea Ostracoda was the collections and reports from the Challenger expedi-

tion (e.g. Brady 1880). Studies of DSDP fossil material (especially Tertiary)

have rekindled interest in the subject of bathyal and abyssal ostracod faunas,

and a selection of some of the more important publications includes Swain

(1970a, 1970b), Benson (1971, 1972, 1974, 1977, 1978), Peypouquet (1975),

Guernet (1982, 1985), Benson & Peypouquet (1983), Whatley (1983, 1985),

Whatley et al. (1983), Whatley & Coles (1987), Whatley & Ayress (1988), and

Hartmann & Hartmann-Schroder (1988). Many of these works relate to specific

or fossil taxa, or are regional surveys, with the result that there have been rela-

tively few documentations of Quaternary faunas in relation to oceanographic

parameters (e.g. water masses, sea-floor sediments). Important studies that have

been made in this category include Rosenfeld & Bein (1978, north-west Africa),

Peypouquet & Benson (1980, south-eastern Atlantic), Benson et al. (1983, New-

foundland), Cronin (1983, Florida), and Steineck et al. (1988, central Pacific).

Our study comprises 46 sample sites in water depths greater than 950 m in

the south-eastern Cape Basin, between 17°S and 35°S (Fig. 1). The samples

were surface sediments (Quaternary) collected in a Van Veen grab from the

University of Cape Town research vessel Thomas B. Davie (TBD) and, with the

exception of the two deepest sites (TBD 6851, 2 916 m; TBD 6852, 4 736 m),

were not stained or preserved in alcohol. A total of 1 059 ostracod valves were

recovered, and only one sample was barren (TBD 3226, 970 m). Thirty-seven

species were isolated and, of these, six species are allochthonous imports

(10 valves, 0,94 per cent total fauna) and four species are residual taxa from

upslope lower Neritic assemblages (63 valves). The 27 genuine deep-water taxa

are represented by 986 valves. Table 1 lists the locations, water depths, and

number of valves for each species. It shows the relatively small numerical data-

base on which we have had to base our study.

Fig. 1. Sample sites in water depths greater than 900 m on the continental margin off south-

western Africa. Numbers are University of Cape Town research vessel ‘Thomas B. Davie’

station numbers for which co-ordinates are given in Table 1. Bathymetry after Dingle et al.

(1987). Insets show locality, and sample sites on a latitude vs depth scattergram.

247

DEEP-WATER QUATERNARY OSTRACODA

Kunene R.

sample distribution

vt (op) N

wy ‘yjJdep 13}eM

Latitude °S

{eo}

LUDERITZ

Orange R.

Olifants R.

CAPE TOWN

tocation

248

ANNALS OF THE SOUTH AFRICAN MUSEUM

TABLE 1

Species distribution (number of valves).

TBD sample no.

Latitude (S)

32.6833

20.9166

33.3666

27.0333

23.2767

19.9167

29.45

24.4333

27.1667

24.5667

23.4383

34.9033

27.9333

25.7917

19.35

20.5833

19.9166

19.9167

20.9166

23.9583

19.3166

SPAINISS)

19.7333

19.9333

21.9

22.9333

26.3833

31.8

34.1

24.4333

25.1166

22.25

20.2333

25.8

29.6166

17.5667

20.9166

34.1083

30.7

31.4167

ZHEOS

28.6333

27.8333

Stoll 7/7)

38.287

Longitude (°E)

16.5167

11.9833

16.8916

13.7167

129/933

IIL a

14.3333

13.15

13.8667

13.2167

12.8276

18.1467

14.2416

13.3083

10.7

11.5

11.0166

10.85

11.7916

12.85

10.52

16.5467

10.4333

10.545

1225

12.5833

13.1166

15.6166

17.4166

12.9833

13.25

12.3417

10.9167

13.1833

14.0333

11.1167

11.625

17.2666

14.8166

15925

13.375

13.9

367)

18.1398

17.1627

Water depth (m)

4 736

Total no. of valves

—

= =

NN ONYNANR We Ree Ne

iSS)

An WS)

Krithe capensis

Krithe rex

Krithe peypouqueti

Krithe sp. 4

11 48 22

Krithe spatularis

Krithe sp. 6

Krithe sp. 7

26 19

Krithe sp. 22

Parakrithe sp. 10

Krithe sp. 19

Krithe sp. 8

14 22

7 oN ROT PO) |) Le oy ame Pen

249

DEEP-WATER QUATERNARY OSTRACODA

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1UYNS DyJanoing

Snpiuoy SiasayjA008ny

Lso¢ ‘ds aayjooqup

1dayvYyM SladayJKIOUIYIT

Ipjafuasos p1uojuNg

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250 ANNALS OF THE SOUTH AFRICAN MUSEUM

PHYSIOGRAPHIC AND OCEANOGRAPHIC SETTINGS

The continental margin off south-western Africa forms the eastern edge of

the Cape Basin, which is further bounded in a clockwise direction by the

Agulhas Ridge, the mid-Atlantic Ridge, and the Walvis Ridge. Abyssal connec-

tions to adjacent deep ocean basins (>4,5 km) are probably limited to two small

sills: via the central Walvis Ridge to the Angola Basin, and adjacent to the

southern tip of Africa to the Agulhas and Mozambique basins. Our samples

come from the continental slope and rise off south-western Africa, which has

been a sediment-starved margin since mid-Tertiary times (Dingle et al. 1987).

The principle physiographic features of this region are slumps. These produce

minor sea-floor irregularities north of 34°S, and major relief, with numerous

small canyons, south of 34°S. Only in the southern region is the continental shelf

narrow and shallow enough to have allowed the advance of the coastline (and

river discharge) to within 30 km of the shelf break during glacial sea-level lows.

Consequently, the potential for allochthonous shelf contaminants on the slope is

relatively low over most of the study area, although at 28°S (just south of Lide-

ritz) the head structures of a large slump lie in a re-entrant of the shelf edge.

The regional physical oceanography along the outer continental margin of

south-western Africa has been summarized by Shannon (1985—see pp. 122-125

mixed layer

Antarctic asa a EN

Intermediate salinity minimum

Water zone poe

North

Atlantic depth

range

Deep studied

for

Water ° ostracods

water depth, km

Antarctic

Bottom

Water

km 600

Fig. 2. Schematic water column structure off south-western Africa superimposed on a bathy-

metric profile across the continental margin south of Liideritz (28°S). Depths for the various

water masses are taken from Shannon (1985). Circled symbols indicate direction of water flow:

+ is towards reader, — is away from reader. Depth range of the ostracod faunas studied is

indicated on the right hand side.

DEEP-WATER QUATERNARY OSTRACODA 254

for full citation of previous works), who identified three major water masses by

their temperature and salinity characteristics. Superimposing these water masses

on a bathymetric profile of the south-eastern Atlantic at 28°S (Fig. 2) shows that

the outer shelf and upper continental slope (<1,5 km) lie under the northward

flowing Antarctic Intermediate Water (AAIW), whereas all the middle to lower

slope, and upper continental rise (>1,5 km) lie under the southward flowing

North Atlantic Deep Water (NADW). Southward flowing Antarctic Bottom

Water (AABW) overlies the lower continental rise and deep ocean floor

(>4,0 km), with the consequence that these deeper regions are below the car-

bonate compensation depth (CCD). The salinity minimum zone within the

AAIW lies between 0,6 and 1,0 km on the upper slope, where its base coincides

with the bathyal thermocline. As we will discuss later, these two physico-

chemical features coincide with the boundary that separates the bathyal from the

neritic ostracod faunas.

TAXONOMY

Abbreviations: ACA = anterior cardinal angle; AM = anterior margin;

ATE = anterior terminal element; DM = dorsal margin; LV = left valve;

ME = median element; MS = muscle scars; PCA = posterior cardinal angle;

PM = posterior margin; PTE = posterior terminal element; RV = right valve;

TE = terminal elements; VM = ventral margin.

Figured specimens are stored at the South African Museum under the cata-

logue numbers SAM—POQ-MF-. SEM numbers refer to unique scanning

electron microscope numbers in the collection of RVD.

Subclass OSTRACODA Latreille, 1806

Order PODOCOPIDA Miller, 1894

Suborder PLATYCOPINA Sars, 1866

Family Cytherellidae Sars, 1866

Genus Cytherella Jones, 1849

The genus Cytherella is widely distributed along the continental margin of

south-western Africa (Fig. 3). Four species have been recognized and these

occupy well-defined depth ranges: Cytherella dromedaria Brady, 1880, and

Cytherella sp. nov. in the Neritic Zone (40-300 m and 115-736 m, respectively),

and C. serratula (Brady, 1880) and Cytherella sp. 3027 in the Bathyal and

Abyssal zones (Fig. 4) (1 000-2 070m, and 2 916m, respectively). Unlike

Krithe and Buntonia, two important genera that range from shallow- to deep-

water environments, neritic species of Cytherella do not extend their depth

ranges into the Bathyal Zone. In this respect Cytherella is similar to

Cytheropteron.

Dp ANNALS OF THE SOUTH AFRICAN MUSEUM

TABLE 2

List of genera and species discussed in this paper.

Local depth

Species range Page

(m)

Cytherella Jones, 1849 Dil

C. serratula (Brady, 1880) 1 000—2 070

Cytherella sp. 3027 2 916

Cytheropteron Sars, 1866 258

C. cronini sp. nov. 990—2 070

Cytheropteron sp. 2909 945

Cytheropteron sp. 2914 2 070

Krithe Brady et al., 1874 263

K. capensis sp. nov. 238-1 430

K. spatulanis sp. nov. 392-1 662

K. rex sp. nov. 2 916

K. peypouqueti sp. nov. 2 916-4 736

Krithe sp. 8 BWR 353)

Krithe sp. 9 430-900

Krithe sp. 4 1 600-2 916

Krithe sp. 6 1 662-2 916

Krithe sp. 7 1 600-2 916

Krithe sp. 19 1 662-2 916

Krithe sp. 22 2 926

Parakrithe van den Bold, 1958a 286

Parakrithe sp. 10 945-1 353

Buntonia Howe, 1935 286

B. rosenfeldi sp. nov. 186—2 070

Dutoitella Dingle, 1981 293

D. suhmi (Brady, 1880) 2 916

Abyssocythere Benson, 1971 298

A. australis Benson, 1971 2 916

Ambocythere van den Bold, 19585 301

Ambocythere sp. 3057 2 070

Echinocythereis Puri, 1954 302

E. whatleyi sp. nov. 730-2 916

Trachyleberis Brady, 1898 309

Trachylebens sp. 3017 2 916-4 736

Henryhowella Puri, 1957 310

H. melobesioides (Brady, 1869) 100-2 916

Rugocythereis gen. nov. 318

R. horridus (Whatley & Coles, 1987) 730-7, 916

Poseidonamicus Benson, 1972 B22

P. major Benson, 1972 2 070-2 916

Indeterminate taxa 328

Indeterminate sp. 62 1 026

Indeterminate sp. 23 1 060

DEEP-WATER QUATERNARY OSTRACODA 253

C. sp. 3027”

ABYSSAL

BATHYAL

water depth, km

C. serratula

C. dromedaria + C.sp. nov.

latitude °S

Fig. 3. Latitude and water depth of samples bearing Cytherella species. There are two species in

each of the Neritic and Bathyal zones: C. dromedaria Brady and Cytherella sp. nov., and

C. serratula Brady and Cytherella sp. 3027, respectively.

NERITIC | BATHYAL | ABYSSAL

UPPER LOWER

100

C. dromedaria

% Cytherella

|S: sp. nov |

| C. serratula

C. sp. S021

water depth, km

Fig. 4. Cytherella species as percentage of total ostracod fauna plotted against water depth.

Note concentrations of samples on the continental shelf (<300 m), and at the Upper/Lower

Bathyal Zone boundary.

254 ANNALS OF THE SOUTH AFRICAN MUSEUM

Cytherella serratula (Brady, 1880)

Fig. SA-C

Cythere (?) serratula Brady, 1880: 77, pl. 43 (figs 7a—d). Puri & Hulings, 1976: 288-289, pl. 24

(figs 15-16).

Cytherella serrulata Brady & Norman, 1896: 713-716, pl. 66 (figs 3-6).

?Cytherella sp. 11 Ducasse & Peypouquet, 1979, pl. 1 (figs 3-4).

?Cytherella sp. Guernet, 1985: 281, pl. 1 (figs 2, 4).

Cytherella sp. B Cronin, 1983, pl. 6 (fig. E).

Cytherella serratula (Brady) Whatley & Coles, 1987: 81, pl. 6 (figs 30-31).

Illustrated specimens

MF-0422, LV, TBD 3344, 1 430 m.

MF-—0423, RV, TBD 3344, 1 430 m.

MF-0424, LV, TBD 3344, 1 430 m.

Remarks

Our material shows slight shape and ornamentation differences to the type

specimens described by Brady (1880), and the lectotypes illustrated by Puri &

Hulings (1976). These, however, are within the range of intraspecific variation

found on an inter-ocean basis (R. C. Whatley citing his own data base, pers.

comm. 1988). Positive identifications of C. serratula (Brady) have been made

from the following sites and depths:

Brady (1880) (Recent)— ‘Challenger’ site 24, Caribbean, 390 fm (713 m); ‘Chal-

lenger’ site 85, Canary Islands, 1 125 fm (2 057m); ‘Challenger’ site 335,

Tristan da Cunha, 1 425 fm (2 605 m).

Brady & Norman (1896) (Recent)— West Africa, 466-1 168 fm (852-2 135 m);

Mauretania, 418-675 fm (764-1 234m); Canary Islands, 487 fm (890 m);

Morocco, 600 fm (1 097 m).

Cronin (1983) (Recent)—south-eastern USA continental slope, 462—1 070 m.

Whatley & Coles (1987) (Miocene to Holocene)—DSDP Leg 94 sites, North

Atlantic, 2 417-3 022 m.

Present study (Recent)—south-western Africa, 1 000-2 070 m.

These records give a modern depth range of 462-3 022 m in the Atlantic.

Cytherella sp. Guernet (1985) from bathyal Eocene sediments at DSDP

site 219 on the 90 East Ridge in the Indian Ocean is very similar to C. serratula

(Brady) in shape and ornamentation, and may be the same species, but differs in

having a small, pronounced dorso-median depression. Cytherella vulgata Rug-

gierl, 1962 (as illustrated by Benson 1978, pl. 2 (fig. 3)), from the Upper

Pliocene at DSDP site 371 also has a similar shape to C. serratula, but has its

highest point in the posterior part of the valve and a more extensive covering of

small spines and granules in the posterior area. Probably the closest species pre-

viously recorded, but not placed in C. serratula (Brady), is Cytherella sp. 11 of

Ducasse & Peypouquet (1979) from bathyal (c. 2 300 m water depth) Pliocene

sediments at DSDP site 403 in the Rockall Basin. These specimens differ slightly

DEEP-WATER QUATERNARY OSTRACODA DS)

BRK

——

Fig. 5. A-C. Cytherella serratula (Brady, 1880), TBD 3344, 1 430 m. A. SAM-PQ-MF-0422,

LV, SEM 2584. B. SAM—-PQ-MF-0423, RV, SEM 2589. C. SAM—POQ-MF-0424, LV internal

view, SEM 2587. D-F. Cytherella sp. 3027, SAM-PQ-MF-0425, RV, TBD 6581, 2 916 m.

D. External view, SEM 3027. E. Detail, postero-ventral area, SEM 3028. F. Detail, antero-

dorsal area, SEM 3029. Scale bar = 100 microns.

256 ANNALS OF THE SOUTH AFRICAN MUSEUM

from our material in having coarser and more extensive spines in the posterior

part of the valve.

Rosenfeld & Bein (1978) recorded smooth species of the genus from the

continental slope off north-west Africa, but illustrated only a coarsely pitted

species, whereas Peypouquet & Benson (1980) noted the genus at 439-2 154 m

in the Cape Basin and 527-2 754 m in the Angola Basin. In neither case did

they illustrate or discuss the species present.

Figures 3 and 4 show the geographical and water-depth distributions of

Cytherella serratula (Brady) in relation to other species of the genus Cytherella

along the continental margin of south-western Africa. It has been found in sedi-

ment samples between approximately 19°S and 33°S (Fig. 3). There is a very

well-defined partitioning of the Cytherella species with water depth (Fig. 4). In

the Neritic Zone, Cytherella sp. nov. extends to 736 m and, together with the

more restricted C. dromedaria Brady, 1880, commonly constitutes greater than

30 per cent of the total ostracod population. There seems to be an hiatus in

occurrence of the genus over the depth range 750-1 000 m, coinciding with the

Salinity Minimum Zone of the Antarctic Intermediate Water Mass. Cytherella

serratula appears at the top of the Bathyal Zone, to which it is restricted, and for

which its appearance and disappearance constitute one of the defining par-

ameters. In the Bathyal Zone, the genus Cytherella (as represented by

C. serratula) is numerically less important than it is higher up the continental

slope, and only reaches 29 per cent in the region of the Upper/Lower Bathyal

Zone boundary (1 430-1610 m). Overall, it forms 3 per cent of the total

bathyal ostracod assemblage (fourth most abundant species), but is somewhat

more important in the Lower Bathyal Zone, where it averages 9 per cent.

Clearly, Cytherella is a sensitive indicator of the different water masses, but is

less tolerant of the conditions in the colder, more saline Bathyal and Abyssal

zones than it is of those in the Neritic Zone. These results are in broad agree-

ment with the data presented by Peypouquet & Benson (1980) from a transect

across the continental margin west of Walvis Bay. Plotting their values we

obtain Figure 6, which shows a decline in percentage of Cytherella in the

ostracod populations from greater than 50 per cent in shallow water (<500 m)

to less than 10 per cent in the water-depth range 974-1 546 m. In deeper water

(2 094 m and 2 117 m) values rise again to approximately 30 per cent.

Cytherella sp. 3027

Fig. 5D-F

?Cytherella sp. gr. ovata (Roemer, 1840) Guernet, 1985: 281, pl. 1 (fig. 1).

Illustrated specimen

MF-0425, RV, TBD 6851, 2 916 m.

DEEP-WATER QUATERNARY OSTRACODA DST

is)

NERITIC BATHYAL

% Cytherella spp.

water depth, km

Fig. 6. Cytherella species as percentage of total ostracod fauna plotted against water depth for a

profile off Walvis Bay. Data computed from Peypouquet & Benson (1980).

Remarks

A single RV, possibly a juvenile. It has a distinctive lateral outline, with

DM sloping towards the PM, a short straight VM, and broadly rounded AM.

The lateral surface has an overall delicate, bead-like reticulation, which is more

pronounced in the anterior and posterior areas. There are small spines along the

postero-ventral margin, and the AM has a very narrow compressed border with

well-separated small pores with setae. There is a triangular depression on the

dorso-median surface that extends as a weak sulcus to the valve centre over the

MS area.

This is probably a new species, which is confined to the upper part of the

Abyssal Zone (2 916 m, TBD 6581).

Guernet (1985) illustrated a very similar specimen from the bathyal Eocene

sediments at DSDP site 219 on the 90 East Ridge in the Indian Ocean.

Cytherella sp. 3027 is the only representative of the genus Cytherella that we

encountered in the Abyssal Zone (i.e. >2 070 m, Fig. 4), where it constitutes

<0,3 per cent of the total ostracod population. In contrast, Peypouquet &

Benson’s (1980) samples from similar depths in the northern Cape Basin off

Walvis Bay contained approximately 30 per cent Cytherella, although they did

not illustrate or describe the species involved. This may indicate a shallowing of

the CCD in the south-eastern Cape Basin, because below 2 154 m, where they

reported very strong dissolution, Peypouquet & Benson (1980, fig. 2) no longer

recorded the genus.

258 ANNALS OF THE SOUTH AFRICAN MUSEUM

Suborder PODOCOPINA Sars, 1866

Superfamily Cytheracea Baird, 1850

Family Cytheruridae Muller, 1894

Genus Cytheropteron Sars, 1866

On the continental margin off south-western Africa, this genus is represented

by 12 species, which occur over a depth range of 40-2 070 m and over a latitudi-

nal range 19°S to 35°S (Figs 7, 8). Nine of these species are confined to the

Neritic Zone (where they occur in two distinct groups—uinner shelf: 40—90 m,

and inner shelf/slope: 80-738 m), and three to the Bathyal Zone. We did not

find the genus in the Abyssal Zone (i.e. deeper than 2 070 m).

In the Neritic Zone, Cytheropteron is locally relatively abundant (up to 45%

total ostracod population in raw data; c. 12% on smoothed curves, Fig. 8),

whereas in the Bathyal Zone it does not exceed 6 per cent in any one sediment

sample. However, the means of its occurrence in both regions are remarkably

constant: 5 per cent in the Neritic Zone, and 4 per cent in the Bathyal Zone.

Overall, we found Cytheropteron to be numerically more important in the

Bathyal Zone: 3,4 per cent of the total ostracod population from samples in

which it occurred in the Bathyal Zone, compared to 1,2 per cent from the

Neritic Zone. There is, however, a significant difference in the distribution of

the various species within the two depth zones. In the Neritic Zone four species

BATHYAL-—

water depth, km

latitude °S

@ — C. cronini

Fig. 7. Latitude and water depth of samples bearing Cytheropteron species. There are nine

species in the Neritic Zone, and three in the Bathyal Zone (see Fig. 8 for depth ranges).

DEEP-WATER QUATERNARY OSTRACODA 259

| nae C.sp. 2914 #

[email protected]. 2909

mC.sp.9

-/———_—__———— C. sp.8

1 C. sp. 7

orn C, SD, 6

bret , SP). ©

mC. sp. 4

™C.sp.3

mC.sp.2

FIC. sp.1

| |

NERITIC BATHYAL

fn UPPER

% Cytheropteron spp.

(0) 1 2

water depth, km

Fig. 8. Cytheropteron species as percentage of total ostracod fauna plotted against water depth.

Values are five point running means. Depth ranges of species are shown by bars. N.B. Neritic

species, Cytheropteron species 1—9, are not further discussed herein.

occur with extensively overlapping depth ranges in the outer shelf/upper slope

region, whereas in the Bathyal Zone only one species has an extensive depth

range (C. cronini sp. nov., 990-2 070 m), with the other two species occurring

only at the upper and lower limits of the Bathyal Zone (Fig. 8).

The upslope limit of the Bathyal Zone is marked by a decrease in the per-

centage of the genus relative to the overall ostracod population (mean 12% to

3%) and, with the exception of sample TBD 3355 (2 070 m), all our records for

the genus are from the Upper Bathyal Zone (Fig. 7). These data indicate that

the genus is sensitive to the physico-chemical changes in the vicinity of the base

of the AAIW low salinity layer, and between the AAIW and the NADW

masses.

260 ANNALS OF THE SOUTH AFRICAN MUSEUM

The depth ranges of the three bathyal Cytheropteron species from off south-

western Africa can be summarized as:

Cytheropteron sp. 2909—945 m (uppermost Bathyal Zone)

Cytheropteron cronini sp. nov.—990-2 070 m (Bathyal Zone)

Cytheropteron sp. 2914—2 070 m (lowermost Bathyal Zone)

Well-documented Quaternary records of the genus from deep-water sites

elsewhere are sparse, and confusing. As Whatley & Masson (1979) have

observed, there have been few detailed revisions of the nineteenth century

works on this genus, with the result that records of earlier-named species are

frequently in error.

In their survey in the south-eastern Atlantic, Peypouquet & Benson (1980)

recorded the following depth ranges for undefined species of the genus: Angola

Basin—527 m; Cape Basin—439-974 m, so that effectively they did not record

it from the Bathyal Zone as we have defined it. Off north-west Africa, Rosen-

feld & Bein (1978) recorded Cytheropteron sp. from 470m, which was the

uppermost part of their ‘deep water’ Association B fauna. Cronin (1983) listed

ten species of Cytheropteron from various depths off south-eastern United

States, seven of which extend into water depths greater than 1 000 m (his Cythe-

ropteron spp. S, D & V, E, B, P, R, and Q). Of these, Cytheropteron sp. P is

probably conspecific with our new species C. cronini from the Cape Basin.

Tressler (1941) illustrated three deep-water species of the genus from the

North Atlantic: Cytheropteron alatum Sars, 1866 (1 280-4 700 m); C. hamatum

Sars, 1869 (1 280 m); and C. inflatum Brady et al., 1874 (1 955-3 230 m), but

comparison of his illustrations with those of Whatley & Masson (1979) indicate

that none are conspecific with the original species. Similarly, Benson et al.’s

(1983) records of C. alatum Sars, 1866 (2 560-2 743 m), and C. testudo Sars,

1869 (1 380-2 758m), off Newfoundland are probably mis-identifications.

Whatley & Masson (1979) noted that dead specimens of C. alatum Sars, 1866,

have been found in 830 m in the Rockall Trough (north-eastern Atlantic).

Deep-water species from atypical deep-water settings have been made by

Breman (1975a, 19756), who described Cytheropteron sp. and C. ‘adriaticur’

from samples between 144-1 216 m in the Adriatic, and Bonaduce et al. (1983),

who recorded three species originally described by Bonaduce et al. (1976)

from ‘deep water’ sites in the Gulf of Aqaba and the Red Sea: C. alabarda,

C. excisum, and C. pulcinella. No water-depth ranges were allocated to

individual species.

Cytheropteron cronini sp. nov.

Fig. 9A-C

?Cytheropteron sp. P Cronin, 1983, pl. 8 (fig. B).

Derivation of name

This species is named for Dr T. M. Cronin (US Geological Survey), who

first recorded the species or a very close relative of it.

DEEP-WATER QUATERNARY OSTRACODA 261

Fig. 9. A—C. Cytheropteron cronini sp. nov, SAM—PQ-MF-0426, holotype, LV, TBD 2880,

1 026 m. A. External view, SEM 2911. B. Detail, ala, SEM 2912. C. Internal view, SEM 3093.

D. Cytheropteron sp. 2909, SAM-PQ-MF-0427, LV, TBD 3341, 945m, SEM 2909.

E-F. Cytheropteron sp. 2914, SAM-PQ-MF-0428, RV, TBD 3355, 2070 m. E. External

view, SEM 2914. F. Detail, ala, SEM 2915. Scale bar = 100 microns.

262 ANNALS OF THE SOUTH AFRICAN MUSEUM

Holotype

MF-0426, LV, TBD 2880, 1 026 m.

Diagnosis

A dolphin-shaped species with delta-like ala that have a large dimple on

their dorsal leading edge. In the dorso-median area there is vertical, slit-shaped

reticulation.

Description

In lateral outline the AM is asymmetrically rounded, and is inclined ven-

trally. PM is asymmetric and bluntly caudate, with the apex dorsally directed.

DM is strongly arched, VM is asymmetrically convex, sloping ventrally towards

the posterior. The central area of the valve is inflated, with a delta-shaped ala

that carries a small spine at its apex. There is a large dimple in the anterior

proximal area of the ala. Valve surface dorsal to the ala is ornamented with low

vertical ribs and slit shaped reticulation. In lateral view there is a small, promi-

nent nick at the posterior end of the DM.

Dimensions (mm)

length height

MF-0426 0,42 0,28

Remarks

This distinctive species (or a close relative) was recorded as Cytheropte-

ron sp. P from 347-1 034 m off Florida by Cronin (1983). Species with similar

features are: C. abyssorum Brady, 1880, from 4 753 m (2 600 fm) off Tasmania,

which has a less triangular ala and stronger surface reticulation; C. trifossata

Whatley & Coles, 1987 (>3 000 m late Quaternary, North Atlantic), which has

more prominent ornamentation and a less posteriorly directed ala; and C. para-

latissimum Swain, 1963 (Pleistocene, Arctic Alaska), whose ala are less posteri-

orly directed and which have ‘subvertical furrows’ on their lateral surface. Cythe-

ropteron porterae Whatley & Coles, 1987 (= C. alatum Sars of Benson et al.

1983), differs in possessing a thickened leading edge to the ala, and is more

coarsely ornamented than C. cronini sp. nov. Whatley & Coles (1987) recorded

C. porterae from the early Pliocene to Quaternary of the North Atlantic.

Cytheropteron cronini is the only species of the genus that has wide geo-

graphical (21°-33°S) and depth (990-2 070 m) ranges in the Bathyal Zone of the

south-eastern Cape Basin (Figs 7, 8).

Cytheropteron sp. 2909

Fig. 9D

Illustrated specimen

MF-0427, LV, TBD 3341, 945 m.

DEEP-WATER QUATERNARY OSTRACODA 263

Remarks

One poorly preserved specimen with a distinct bevel along the outer edge of

its ala, in the centre of which there is a small depression. The lateral surface may

have originally been coarsely punctate. Despite its battered appearance, we con-

clude that this specimen is not allochthonous because no provenance population

has been located farther upslope. It occurs at the top of the Upper Bathyal

OIC:

In general shape this species is similar to Cytheropteron sp. Q, recorded by

Cronin (1983) from 584 m (?382 m) to 1070 m off the south-eastern United

States.

Cytheropteron sp. 2914

Fig. 9E—F

Illustrated specimen

MF-0428, RV, TBD 3355, 2 070 m.

Remarks

A fragile species with a small, sharp ala that bears two small spines, and has

a corded leading edge. The sculptured postero-dorsal margin is similar to that of

Cytheropteron sp. 8 of Ducasse & Peypouquet (1979, pl. 4 (fig. 7)) from the

Quaternary of DSDP site 400A (north-eastern Atlantic). The latter has an area

of coarse reticulation dorsal to the ala, which in Cytheropteron sp. 2914 is

covered by a feint, longitudinally sinuous ridge. This species is a close relative of

C. syntomoalatum Whatley & Coles, 1987 (see pl. 2 (fig. 27)), from the late

Pliocene to Quaternary of the North Atlantic, particularly in possessing a mid-

dorsal ‘cross’. Differences in ornamentation and structure of the ala apex may

indicate that the two are not conspecific.

Cytheropteron sp. 2914 was encountered only in the lowermost part of the

Lower Bathyal Zone.

Family Cytherideidae Sars, 1925

Genus Krithe Brady, Crosskey & Robertson, 1874

The genus Krithe and the closely related genus Parakrithe have convention-

ally been regarded as indicators of ‘deep’ water (e.g. Van Morkhoven 1962),

and use has recently been made of variations in shell architecture to semi-

quantitively predict palaeo-water depths and dissolved oxygen levels (e.g.

Peypouquet 1975, 1979; Donze et al. 1982). The latter studies have been based

on numerous morphotypes that, whilst they have not attempted to systematically

isolate species, have shown that this group is taxonomically complex and diverse

(e.g. Peypouquet 1979). Whatley (1983) recorded that, with the exception of

264 ANNALS OF THE SOUTH AFRICAN MUSEUM

Cytheropteron (57 species), Krithe (54 species) is the most diverse genus in the

Quaternary ostracod faunas of the bathyal and abyssal regions of the south-

western Pacific.

Similarly, Krithe (together with one species of Parakrithe) and Cytheropte-

ron are the two most diverse genera in the deep-water faunas off south-western

Africa (12 species each), whereas in the Abyssal Zone the genus Krithe is the

most abundant taxon. It occurs across the entire latitudinal range of our study

area (17°S to 38°S), and is found over a more extensive water-depth range than

any Other genus (238—4 736 m, Fig. 10). With one exception (Krithe sp. 9), all

the species are found in either bathyal or abyssal depths, and five also occur in

the Neritic Zone (Fig. 13). On a regional scale, variations in the abundance of

Krithe within the overall ostracod populations have been used (together with

Henryhowella melobesioides (Brady, 1869) and Buntonia rosenfeldi sp. nov.) to

help identify the limits of the faunal zones off south-western Africa (see

Figs 54, 55).

Figure 11 shows that the abundance of Krithe species (as a percentage of

the total ostracod fauna) varies greatly over the water-depth range of the genus,

and that there is not a simple progressive increase in values oceanward. This can

be further emphasized when mean values for individual depth zones are exam-

ined: Figure 12 shows that, although the overall trend is Neritic (19%) through

——® = K. capensis

—-—D = Parakrithe sp.10

water depth, km

latitude °S

Fig. 10. Latitude and water depth of samples bearing Krithe species and Parakrithe sp. 10. The

distributions of Krithe capensis sp. nov. and Parakrithe sp. 10 are outlined.

DEEP-WATER QUATERNARY OSTRACODA 265

| | _

| | mJ

| ees ee ey

depth Moe cee ees

ranges SSS SS SS

-}-———1E

ee ae

7 RAE gee Da Ee

I =

dominant | fi ea AE uh 4sp.4 peypouqueti

i Spatularis

species ea |

->——————_icapensis | |

NERITIC BATHYAL ABYSSAL

UPPER | LOWER

fo)

if]

% Krithe spp.

0) 1 2 3 4 5

water depth, km

sp. 7

. sp. 6

. sp. 19

rex

. sp. 22

. peypouqueti

. Capensis

. spatularis

sp. 9

. sp. 8

arakrithe sp. 10

. sp. 4

mmodowowp

RUAKRAZA

Ros & — 2c ®)

RAKRARKRA

Fig. 11. Krithe species (including Parakrithe sp. 10) as percentage of total ostracod fauna

plotted against water depth. Values are three point running means. In the upper part of the

diagram ‘depth ranges’ show bars for total range of individual species of Krithe and one species

of Parakrithe identified A-L in the list in lower part of figure. Krithe sp. 9, which is a neritic

taxon, is included for completeness. ‘Dominant species’ shows depth range bars for particular

species dominating the Krithe assemblage, and are derived from variations in abundance shown

in Figure 13.

266 ANNALS OF THE SOUTH AFRICAN MUSEUM

Bathyal (24%) to Abyssal (42%), there is a decrease from Neritic into Upper

Bathyal (13%), and a decrease from Lower Bathyal (51%) into Abyssal. These

fluctuations can be related to the environmental tolerances of particular species,

and we recognize two groups: an Upper Krithe Fauna that occurs in the Neritic

and Upper Bathyal zones (238-1 500 m); and a Lower Krithe Fauna that occurs

in the Lower Bathyal and Abyssal zones (1 500-4 736 m) (Figs 11, 13A—B, 14).

Throughout most of the Neritic Zone, the Upper Krithe Fauna is domi-

nated by Krithe capensis sp. nov., but this species declines sharply in abundance

across the Neritic/Bathyal boundary, below which it is effectively replaced by

Krithe sp. 8. Krithe capensis also suffers a temporary decline in abundance

between approximately 500 m and 700 m water depth, where there is also a

sharp decline in the importance of the genus as a whole across the upper bound-

ary of the salinity minimum zone of the AAIW. Within this narrow depth range,

as well as over the lower part of the Upper Bathyal Zone (where the genus as a

whole is again relatively poorly represented), Krithe spatularis sp. nov. replaces

K. capensis as the dominant species.

The genus Krithe reaches a low level of abundance within the ostracod

populations at the base of the Upper Bathyal Zone (i.e. at the base of the

AAIW mass) where, over the depth range 1 430 m to 1 525 m, all four extant

LOWER

BATHYAL

ABYSSAL

total ostracods

NERITIC

mean %

% range = 1—64 Samos 20-100 14-66

n = 30 10 5 3

Fig. 12. The mean percentage of Krithe species for the four depth zones. Values are calculated

on samples in which Krithe occurs, and not on the overall ostracod fauna. Mean value for the

Bathyal Zone is 24%; n = number of samples.

% Krithe spp.

DEEP-WATER QUATERNARY OSTRACODA 267

| |

NERITIC | BATHYAL | ABYSSAL

| |

UPPER | LOWER

100

UPPER KRITHE FAUNA

= K. capensis

K. spatularis

100 |

LOWER KRITHE FAUNA

| . peypouqueti

water depth, km

Fig. 13. Variation in abundance of individual Krithe species with water depth (plotted as a

percentage of the Krithe assemblage). A. Upper Krithe Fauna (three-point means). B. Lower

Krithe Fauna (three-point means, and raw data in deepest sample). Ranges over which particu-

lar species dominate are shown in Figure 11.

268 ANNALS OF THE SOUTH AFRICAN MUSEUM

LOWER

BATHYAL

water depth, km

NERITIC

latitude °S

— O = K. capensis

--— += K. spatularis

Fig. 14. Latitude and water depth of samples bearing Krithe capensis, K. spatularis, and

Krithe sp. 8. The open arrow locates a possible allochthonous occurrence of K. capensis.

species of the Upper Krithe Fauna die out (K. capensis, K. spatularis, Krithe

sp. 8, and Krithe sp. 9). There is a dramatic increase in the abundance of the

genus in the Lower Bathyal Zone with the incoming of four species of the Lower

Krithe Fauna (Krithe sp. 4, Krithe sp. 6, Krithe sp. 19, and Krithe sp. 7). Of

these, Krithe sp. 4 dominates the Lower Bathyal and upper parts of the Abyssal

zones, before it and the three other species are themselves replaced by the true

abyssal species at 2 916 m. The most important abyssal taxon is the relatively

small, globular Krithe peypouqueti sp. nov.

A summary of the species of Krithe that dominate at the various depths off

south-western Africa is given in Figure 11.

Peypouquet & Benson (1980) recorded the distribution of Krithe and Para-

krithe in their transect west of Walvis Bay, but the relative sparsity of data

points precludes a detailed comparison with our data (Fig. 15). The overall

picture is of a significant increase in abundance across the Neritic/Bathyal

boundary, and a decrease in Abyssal depths. The highest values occur within the

Bathyal Zone, and in this respect their data agrees with our own.

DEEP-WATER QUATERNARY OSTRACODA 269

NERITIC BATHYAL ABYSSAL

UPPER

[o)

% Krithe spp.

1 2 3

water depth, km.

Fig. 15. Krithe species as percentage of total ostracod fauna plotted against water depth for a

profile off Walvis Bay. Data computed from Peypouquet & Benson (1980).

Krithe capensis sp. nov.

Figs 16A-—C, 17A, 18D

Krithe spp. Boomer, 1985: 57-58, pl. 4 (fig. 63).

Derivation of name

From the Cape Basin.

Holotype

MF-0429, LV, TBD 2879, 530 m.

Paratypes

MF-0431, LV, TBD 2879, 530 m.

MF-0430, RV, TBD 3577, 453 m.

MF-0450, LV, TBD 3577, 453 m.

Diagnosis

In lateral view, the highest point of the valve lies in the posterior third, over

a broadly rounded postero-dorsal arch. VM is straight, AM is broadly rounded.

270 ANNALS OF THE SOUTH AFRICAN MUSEUM

Description

In external view, the valves have a high, broadly rounded arch over the pos-

terior dorsal region. AM in the LV is broadly rounded and almost symmetrical,

whereas the AM in the RV is slightly upturned and there is a subtle antero-

dorsal step. The PM depression is prominent and elliptical, but partly hidden in

internal lateral view. The anterior vestibule is moderately large and has two

lobes on the dorsal side. The anterior inner margin descends from the dorsal

margin in almost a straight line, and forms an acute angle antero-ventrally. MS

have a partly subdivided dorsal-most adductor, and a lobed anterior scar.

Dimensions (mm)

length height

MF-0429 0,91 0,50

MF-0431 0,90 0,51

MF-0430 0,95 0,50

MF-0450 0,99 0,50

The mean length/height ratio of the type specimens is 1,86, which distin-

guishes Krithe capensis in the local deep-water faunas from all but Krithe sp. 4

(Figs 19, 20).

Remarks

We have difficulty in assigning K. capensis sp. nov. to the ‘ecotypes’

described by Peypouquet (1979), but on balance it has most in common with his

category C.

Krithe capensis is quite close to K. nibelaensis Dingle from the Campanian

to Eocene of southern Africa (Dingle 1981; Frewin 1987), but their MS patterns

differ in the shape of the anterior scar, and the former species has a more arched

postero-dorsal valve outline. Rosenfeld & Bein (1978, pl. 1 (fig. 20)) illustrated

a species with a similar inner margin outline to K. capensis, which they allocated

to K. producta? Brady, 1880. Our species differs from theirs in its more arched

postero-dorsal outline and less prominent and incised posterior depression. The

lectotype of K. producta Brady, 1880 (Puri & Hulings 1976), has a more

rounded PM and broadly arched DM outline than K. capensis. Benson &

Peypouquet (1983, pl. 5 (fig. 5)) illustrated a specimen (Krithe sp. C23) from

the Lower Miocene of DSDP site 516 that has a similar shaped vestibule to

K. capensis, but this species has parallel VM and DM.

Off south-western Africa, we have found Krithe capensis within the latitudi-

nal range 17°S to 35°S (Fig. 10). Its depth range is 238-1 430 m (a total of

1 192 m), which includes the outer shelf (Neritic Zone) through to the upper-

most part of the Lower Bathyal Zone. This suggests that K. capensis is the most

euryhaline and eurythermal Krithe species in our study area (34,9-34,6%o to

<34,4%o, 10°C to 3,2-3,6°C). Variations in its abundance in relation to other

species of the genus (Fig. 13) indicate that K. capensis is the dominant species

DEEP-WATER QUATERNARY OSTRACODA OFM

Fig. 16. A-C. Krithe capensis sp. nov. A. SAM-PQ-MF-0429, holotype, LV, TBD 2879,

530m, SEM 2709. B. SAM-—PQ—-MF-0430, RV, TBD 3577, 453m, SEM 2714.

C. SAM-PQ-MF-0431, LV internal view, TBD 2879, 530m, SEM 2710. D-F. Krithe

spatularis sp. nov. D. SAM—PQ-MF-0432, holotype, LV internal view, TBD 2978, 736 m,

SEM 2707. E. SAM-—PQ-MF-0433, RV, TBD 2978, 736m, SEM 2705. F. SAM-

PQ-MF-0434, LV, TBD 3177, 1 000 m, SEM 2702. Scale bars = 100 microns.

272 ANNALS OF THE SOUTH AFRICAN MUSEUM

on the continental shelf and uppermost slope, but over the depth range

c. 500-700 m it is replaced by K. spatularis sp. nov. This coincides with the part

of the AAIW mass that lies immediately above the Salinity Minimum Zone (see

Fig. 2). Within the Salinity Minimum Zone, K. capensis reverts to its dominant

position but, from about 950 m to the depth at which it dies out (1 430 m), it

declines rapidly in abundance. At the Neritic/Bathyal boundary (950 m) it is

replaced by Krithe sp. 8., and at deeper levels by K. spatularis sp. nov. Its lower

limit is apparently defined by the AAIW/NADW shear zone boundary (Upper/

Lower Bathyal boundary). All our evidence suggests that in the south-eastern

Cape Basin, K. capensis is the most tolerant of low-salinity conditions of all the

species of the genus.

A more critical assessment of the geographical distribution of Krithe capen-

sis (Fig. 14) suggests that the deepest site at which the species has been located

may in fact represent an allochthonous occurrence. We suspect this because the

three sites astride the Neritic/Bathyal boundary lie along a wide front from

which station TBD 3344 (1 430 m) is isolated. If this is the case, then the depth

range of this species is 238-1 071 m (a total of 833 m), and K. capensis would

more correctly be considered a neritic species that only straggles into the deep-

water assemblages in the Upper Bathyal Zone, just below the base of the Salin-

ity Minimum Zone of the AAITW. At present we have insufficient data to

confirm this suspicion, and take the data at face value.

Krithe spatularis sp. nov.

Figs 16D-F, 17B, 18E

Derivation of name

Latin spatula—spoon, allusion to spoon- or spatula-like lateral outline.

Holotype

MF-—0432, LV, TBD 2978, 736 m.

Paratypes

MF-0433, RV, TBD 2978, 736 m.

MF-0434, LV, TBD 3177, 1 000 m.

MF-0451, RV, TBD 3555, 590 m.

Diagnosis

Species with a compressed, spatula-shaped anterior lateral outline, and a

deep, cleft-like posterior depression.

Description

In external lateral view, AM is broadly and symmetrically rounded. The

antero-dorsal and AM areas are compressed, giving a spatula-like appearance.

DEEP-WATER QUATERNARY OSTRACODA DAS

aes

Q R

Fig. 17. Outlines of various species of Krithe and Parakrithe. A. Krithe capensis sp. nov.,

SAM-PQ-MF-0450, LV, TBD 3577, 453m. B. Krithe spatularis sp. nov., SAM-—PQ

—MF-0451, RV, TBD 3555, 590 m. C. Krithe sp. 8, SAM—PQ-MF-0452, LV, TBD 3177,

1000 m. D. Krithe sp. 4, SAM—PQ-MF-0453, RV, TBD 3355, 2 070 m. E-F. Krithe sp. 7,

TBD 6851, 2 916m. E. SAM-—PQ-0454, LV. F. SAM-PQ-MF-0446, RV. G-H. Krithe

rex sp. nov., TBD 6851, 2 916 m. G. SAM—PQ-MF-0456, RV. H. SAM—PQ-MF-0438, LV.

I. Parakrithe sp. 10, SAM-—PQ-MF-0449, RV, TBD 3553, 1003m. J-K. Krithe sp. 6,

TBD 6851, 2 916 m. J. SAM—PQ-—MF-0457, LV. K. SAM—PQ-MF-—0445, RV. L-M. Krithe

peypouqueti sp. nov., TBD 6851, 2916m. L. SAM-—POQ-MF-0441, LV. M. SAM-

PQ-MF-0439, RV. N. Krithe sp.9, SAM-PQ-MF-0443, RV, TBD 3524, 475 m.

O-P. Krithe sp. 19, TBD 6851, 2916m. O. SAM-PQ-MF-0447. Q-R. Krithe sp. 22,

TBD 6851, 2 916 m. OQ. SAM—PQ-MF-0458, LV. R. SAM-PQ-MF-0448, RV.

Scale bar = 500 microns.

274 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 18. Details of anterior marginal areas of Krithe and Parakrithe, placed in order of lower

depth limit of species. All internal views. A. Krithesp.9, SAM-—PQ-MF-0443,

RV, TBD 3524, 475 m. B. Parakrithe sp. 10, SAM—PQ-—MF-0449, RV, TBD 3553, 1 003 m.

C. Krithe sp. 8, SAM—PQ-—MF-0452, LV, TBD 3177, 1 000m. D. Krithe capensis sp. nov.,

SAM-PQ-MF-0450, LV, TBD 3577, 453m. E. Krithe spatularis sp. nov., SAM-—PQ-

MF-0451, RV, TBD 3555, 590 m. F. Krithe sp. 4, SAM-PQ-MF-0453, RV, TBD 3355,

2070m. G. Krithe sp.6, SAM-PQ-MF-0457, LV, TBD 6851, 2916m. H. Krithe

rex sp. nov., SAM-—-PQ-MF-—0438, ?female, LV, TBD 6851, 2916m. I. Krithe sp. 19,

SAM-PQ-MF-0447, RV, TBD 6851, 2916m. J. Krithe sp. 7, SAM-—POQ-MF-0454, LV,

TBD 6851, 2916m. K. Krithe sp. 22, SAM-—PQ-MF-0448, RV, TBD 6851, 2 916m.

L. Krithe peypouqueti sp. nov., SAM-PQ-MF-0439, holotype, RV, TBD 6851, 2 916 m.

Scale bar = 500 microns.

DM and VM parallel, although there is a slight concavity at about mid-length in

the VM. PM asymmetric, sloping steeply to a ventral apex. In internal view, the

posterior depression is very prominent and lies in a deep, ventrally open cleft.

Anterior vestibule is large and posteriorly wide. Outline of inner margin is sym-

metrically rounded, with an anterior apex.

DEEP-WATER QUATERNARY OSTRACODA Das)

Dimensions (mm)

length height

MF-0432 1,09 0,55

MF-—0433 IBO2 0,50

MF-0434 let OSs

MF-0451 Le 0,49

The mean length/height ratio of the type specimens is 2,07, which is the

highest value we have recorded amongst the large species of Krithe in our study

(Figs 19, 20).

Remarks

The distinctive shape of the new species has no close analogues from

southern Africa, but is similar to the following species from elsewhere:

K. hiwanneensis Howe & Lea, 1936, from the Oligocene of Louisiana (which is

not compressed anteriorly); K. oertlii Dieci & Russo, 1967, from the Miocene of

Italy (which does not have a straight DM); and K. vandenboldi Steineck, 1981,

from the Miocene of Jamaica (which is a smaller species with a slightly concave

VM outline, and a differently shaped anterior vestibule).

Krithe spatularis sp. nov. would seem to fit into the ‘ecotype’ Krithe sp. F of

Peypouquet (1979), which he suggested is an indicator of low dissolved O2 in the

water column.

0-6 2 (a)

7 /

fl /, peypouqueti

,ao,

S27

E ve Qo) Mal

; { \_

E05 eee ao

iS . .

2 capensis spatularis

0:4

sp 224 Tey) 2 ah

> oa a a

‘ol = eae 2S exe

Nee en Z

(a o> sp.19

0:3

length, mm

©) = capensis N = sp.7 & = spatularis @ = rex

Fig. 19. Length versus height scattergram of Krithe species. Data points are specimens

illustrated herein.

276 ANNALS OF THE SOUTH AFRICAN MUSEUM

O spatularis

co Capensis

sp. 4

mean length/height

O peypouqueti

0-7 0:8 0-9 1:0 11

mean length, mm

Fig. 20. Ratios of mean length/mean height plotted against mean lengths for the illustrated

specimens of the various species of Krithe.

Off south-western Africa, K. spatularis has a latitudinal range 19°S to 35°S,

and a depth range 392-1 662 m (a total of 1 272 m) (Figs 13, 14). It is most

abundant (relative to other species of the genus) at those levels where K. capen-

sis is relatively unsuccessful, i.e. immediately above the Salinity Minimum Zone

in the AAIW (lower Neritic Zone), and in the lower part of the Upper Bathyal

Zone, although we never recorded it exceeding 3 per cent of the total ostracod

population. Despite a greater depth range than K. capensis, K. spatularis prob-

ably tolerates a narrower salinity and temperature range (34,8-34,5%o to

<34,6%0; 8,5—6°C to 3,2—2,8°C), because of its deeper upper depth limit.

Krithe rex sp. nov.

Figs 17G—H, 18H, 21A—D

?Krithe sp. C Cronin, 1983, pl. 10 (figs B—C).

Derivation of name

Latin rex—king, allusion to large, bold species.

Holotype

MF-—0435, RV, male, TBD 6851, 2 916 m.

DEEP-WATER QUATERNARY OSTRACODA Die,

Paratypes

MF-0436, RV, female, TBD 6851, 2 916 m.

MF-0437, RV, male, TBD 6851, 2 916 m.

MF-0438, LV, ?female, TBD 6851, 2 916 m.

MF-0456, RV, male, TBD 6851, 2 916 m.

Diagnosis

Large species with humped DM and convex VM. There is a prominent

antero-dorsal step in lateral outline.

Description

A large species, with a distinctive, bold shape and marked sexual dimor-

phism. In external lateral view, AM is broadly rounded, PM is truncated and

short, sloping to a postero-ventral apex. The DM is strongly arched, particularly

in the shorter (presumed) females, in which the convex VM is also more promi-

nently developed. The central area of the valves is somewhat inflated. In

internal view, the posterior depression is clearly visible but is neither large nor

incised. The anterior inner lamella is wide but the vestibule is relatively small

and complex in shape, lying between the anterior margin and two large lobe-like

re-entrants in the line of concrescence. The inner margin outline has a small

neck-like incision that links the vestibule to the interior of the shell. This may

represent a weak zone that preferentially suffers abrasion. The MS consist of a

forward pointing V-shaped anterior scar, with a small super-adjacent scar, and

four elongate adductors, the most dorsal of which is partially subdivided.

Dimensions (mm)

length height

MF-0435 1,15 0,60

MF-0436 1,18 OMS

MF-0437 1,12 0,51

MF-0438 1,18 0,65

MF-—0456 Ly 0,60

The mean length/height ratio of the type specimens is 1,96. When plotted

against valve length (Fig. 20), Krithe rex is seen to be a more elongate taxon

than Krithe sp. 7 and Krithe sp. 8, with which it has an overlapping length/height

field on the scattergram (Fig. 19).

Remarks

This is the largest species of the genus Krithe in the ostracod populations off

south-western Africa (the holotype is 1 150 microns in length), and can be

assigned to Peypouquet’s (1979) category D2.

No species analogous to Krithe rex has been recorded from southern Africa,

but the following species from elsewhere are similar in general appearance:

Krithe cubensis van den Bold, 1946, from the Oligocene of Cuba (which is less

inflated, and possesses relatively large vestibules); Krithe morkhoveni van den

278 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 21. A-D. Krithe rex sp. nov. TBD 6851, 2 916m. A. SAM—PQ-MF-0435, holotype,

male, RV, SEM 2691. B. SAM-—PQ-MF-0436, female, RV, SEM 2694. C. SAM-

PQ-MF-0437, male, RV internal view, SEM 2701. D. SAM—POQ-MF-0438, ?female, LV.

E-F. Krithe peypouqueti sp. nov. TBD 6851, 2 916m. E. SAM—PQ-MF-0439, holotype,

RV. F. SAM—POQ-MF-0440, LV, SEM 2695.

Scale bars: B = 200 microns, others = 100 microns.

DEEP-WATER QUATERNARY OSTRACODA 279

Bold, 1960, from the Miocene of Trinidad (which is a much smaller species, has

a different MS pattern, and possesses relatively large vestibules); K. trinidaden-

sis van den Bold, 1958a, from the Oligocene to Miocene of Trinidad (which has

a less strongly arched DM and the males have a more acuminate PM outline

than K. rex sp. nov.). Brady (1880, pl. 27 (fig. /)) illustrated a species as Krithe

producta (probably not conspecific with the lectotype designated by Puri &

Hulings 1976), which lacks the LV antero-dorsal step.

Cronin (1983) illustrated a species (Krithe sp. C, pl. 10 (figs B—C)) from his

deepest sample off Florida (1 070 m), which may be conspecific with Krithe rex

sp. nov. and is the closest relative that we have observed in the literature. Guer-

net’s Krithe sp. 1 (1985, pl. 1 (fig. 16)) from the Upper Eocene of DSDP

site 214 (90 East Ridge, Indian Ocean) also has a similar lateral outline,

although its VM is somewhat less convex.

Off south-western Africa, we have recovered Krithe rex at only one site

(TBD 6851) at a water depth of 2 916 m, where it constitutes 3 per cent of the

total ostracod population and 6 per cent of the Krithe population. In our area it

is clearly an abyssal species, but if Cronin’s (1983) Krithe sp. C is conspecific,

then in the north-western Atlantic at least, the species ranges into the depths

equivalent to the Upper Bathyal Zone as we define it in the south-eastern

Atlantic.

Krithe peypouqueti sp. nov.

Figs 17L—M, 18L, 21E-F, 22A

Derivation of name

The species is named for Dr J.-P. Peypouquet (University of Bordeaux) for

his work on the genus Krithe.

Holotype

MF-0439, RV, TBD 6851, 2 916 m.

Paratypes

MF-0440, LV, TBD 6851, 2 916 m.

MF-0441, LV, TBD 6851, 2 916 m.

Diagnosis

A globular species with a rounded DM, and a strong antero-dorsal step in

the RV lateral outline.

Description

A squat, globular species in lateral view. AM broadly rounded, PM asym-

metrically rounded, truncated in LV. DM strongly arched and rounded, with a

prominent antero-dorsal step in the RV. VM broadly convex. Central valve area

is inflated. In internal view, the inner margin runs approximately parallel to the

AM, and the inner lamella and vestibule are narrow.

280 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 22. A. Krithe peypouqueti sp. nov., SAM—PQ-—MF-0441, LV, TBD 6851, 2 916 m. B-C.

Krithe sp. 8, SAM—PQ-MF-0442, TBD 3177, 1000 m. B. RV internal view, SEM 2715.

C. External view. D. Krithe sp. 22, SAM-PQ—MF-0448, RV, TBD 6851, 2 916 m. E. Krithe

sp. 4, SAM—POQ-MF-—0444, RV, TBD 3355, 2 070 m. F. Krithe sp. 6, SAM-PQ-—MF-0445,

RV, TBD 6851, 2 916 m. Scale bars = 100 microns.

DEEP-WATER QUATERNARY OSTRACODA 281

Dimensions (mm)

length height

MF-—0440 0,81 0,60

MF-0439 0,78 0,56

MF-0441 0,79 0,56

The mean length/height ratio of the type specimens is 1,38, which combined

with its mean length values (0,79 mm) easily distinguishes Krithe peypouqueti

from all other species of the genus that occur off south-western Africa

(Figs 19, 20).

Remarks

The species most similar in lateral outline to Krithe peypouqueti sp. nov.

that we have encountered in the literature is a specimen recorded by Guernet

(1983, pl. 1 (fig. 15)) under Krithe sp. 1 (his category is clearly poly-specific)

from the Upper Eocene of DSDP site 214 on the 90 East Ridge. However, this

species has a wide inner lamella.

Off south-western Africa, Krithe peypouqueti has a depth range

2 916—4 736 m, and is one of the most abundant ostracod species in the Abyssal

Zone. At Site TBD 6851 (2 916 m), it constitutes 13 per cent of the total ostra-

cod fauna (second in abundance to Poseidonamicus major) and 28 per cent of

the Krithe population (the most abundant species of the genus). At site 6852

(4 736 m, where only three valves were recovered), Krithe peypouqueti forms

66 per cent of the total ostracod fauna.

OTHER SPECIES OF KRITHE

Neritic/Bathyal species

Krithe sp. 8

Figs 17C, 18C, 22B-—C

Illustrated material

MF-0442, RV, TBD 3177, 1 000 m.

MF-0452, LV, TBD 3177, 1 000 m.

Remarks

This is a relatively large species (see Fig. 19) that has a distinctive postero-

dorsal arch, giving it a ‘humped back’ appearance in lateral view. Its overall

outline is similar to Krithe rex sp. nov., but it is somewhat less elongate (mean

length/height ratio = 1,84) (Fig. 20). The posterior depression is deep, rounded,

and set in a wide flat furrow. The inner lamella is relatively wide, with large

anterior vestibules, and the outline of the inner margin is asymmetrically

282 ANNALS OF THE SOUTH AFRICAN MUSEUM

rounded, with an antero-ventral apex. MS consist of an irregular U-shaped and

small elongate anterior set, and four elongate adductors, the dorsalmost of

which is almost subdivided.

Krithe sp. 8 has a depth range of 530-1 353 m off south-western Africa (i.e.

Neritic to Upper Bathyal) and, although it is generally rare (1-6% total ostra-

cod fauna), the species appears to opportunistically exploit an environmental

niche at the Neritic/Bathyal boundary. Here, straddling the base of the Salinity

Minimum Zone, it is the most abundant species in the Krithe population (up to

11% of the total ostracod fauna, and >80% of the Krithe fauna), locally sup-

planting the two important taxa in the Upper Krithe Fauna (Krithe capensis and

K. spatularis) (see Figs 11, 13).

Krithe sp. 9

Figs 17N, 18A, 23C

Illustrated material

MF-0443, RV, TBD 3524, 475 m.

Remarks

Although not a bathyal species, we include a record of Krithe sp. 9 for com-

pleteness. This is a sub-quadrate, elongate species with a large and complex

anterior vestibule. It has a depth range of 430—900 m, so that its lower range

overlaps with Krithe capensis, K. spatularis, and Krithe sp. 8.

Bathyal/Abyssal species

Four species of Krithe appear immediately below the Upper/Lower Bathyal

boundary (i.e. at the top of the NADW mass). These constitute the taxa in the

upper part of the Lower Krithe Fauna: Krithe sp. 4, Krithe sp. 6, Krithe sp. 7,

and Krithe sp. 19 (Figs 11, 13).

Krithe sp. 4

Figs 17D, I8SE, 22E

Illustrated material

MF-0444, RV, TBD 3355, 2 070 m.

MF-0453, RV, TBD 3355, 2 070 m.

Remarks

This is a relatively large quadrate species, with a distinctively truncated PM

outline in lateral view. On the length/height scattergrams, this species occupies a

field between the species with mean lengths >1,00 mm and K. capensis (Figs 19,

20). The anterior vestibule is moderately large and widens anteriorly from a

DEEP-WATER QUATERNARY OSTRACODA 283

narrow posterior ‘neck’. The outline of the inner margin has a rounded apex at

about mid-height. None of our adult specimens had well-preserved hinges but

there appears to be a strong, elongate, tooth-like structure at the anterior end of

the RV ME. The single anterior MS has three anteriorly directed lobes.

Krithe sp. 4 has a depth range 1 600-2 916 m off south-western Africa. It is

the dominant species of the Lower Krithe Fauna in the Lower Bathyal and

upper Abyssal levels (2% of total ostracod fauna), below which it is replaced by

K. peypouqueti (Figs 11, 13). This distribution pattern suggests that Krithe sp. 4

is tolerant only of the physico-chemical environments found in the upper part of

the NADW mass.

Krithe sp. 6

Figs 17J-K, 18G, 22F

Illustrated material

MF-0445, RV, TBD 6851, 2 916 m.

MF-0457, LV, TBD 6851, 2 916 m.

Remarks

A moderate-sized species with a semi-elliptical outline in lateral view, in

which the RV posterior margin has a small re-entrant in the vicinity of the pos-

terior depression. With the exception of Krithe peypouqueti, the mean

length/height ratio of 1,58 is the lowest that we have recorded for a species of

Krithe and gives this species an isolated position on scattergrams (Figs 19, 20).

The vestibules of Krithe sp. 6 are very narrow, with the inner margin lying close

and parallel to the outer margin. MS appear complex, with three small anterior

scars and four adductors.

Krithe sp. 6 has a depth range of 1 662-2 916 m. The species is a minor

component of the Lower Krithe Fauna, but is relatively more abundant in the

Lower Bathyal Zone.

Krithe sp. 7

Figs 17E-F, 18J, 23A

Illustrated material

MF-0446, RV, TBD 6851, 2 916 m.

MF-0454, LV, TBD 6851, 2 916 m.

Remarks

A relatively large species with a mean length/height ratio of 1,89 (Fig. 20).

In external lateral view, the species is characterized by a broadly rounded AM

that contrasts with a somewhat extended PM, which in the RV has a small

284 ANNALS OF THE SOUTH AFRICAN MUSEUM

re-entrant above the posterior depression. The DM is gently convex, which

helps to distinguish it from Krithe sp. 4. The anterior inner lamella is moderately

wide but the vestibule is small and almost rectangular in shape.

Krithe sp. 7 has a depth range 1 600-2 916 m. The species is a minor com-

ponent of the Lower Krithe Fauna but is relatively more abundant in the Lower

Bathyal Zone, particularly in the uppermost part.

Krithe sp. 19

Figs 170-P, 181, 23B

Illustrated material

MF-0447, RV, TBD 6851, 2 916 m.

Remarks

A small elongate species that has the highest mean length/height ratio

within the Krithe populations that we studied (2,30—Figs 19, 20). In external

lateral view, Krithe sp. 19 is characterized by prominent re-entrants in both

valves, above the posterior depression, that give the valve a ‘pleated’ appear-

ance. The anterior vestibules are small, and largely lie anterior to two lobes in

the marginal zone. The anterior MS appears to consist of a cluster of three small

scars.

Krithe sp. 19 has a depth range 1 662-2 916 m. Although it occurs in small

numbers (maximum of 4% total ostracod fauna at TBD 6851), it is the second

most abundant taxa of the Lower Krithe Fauna throughout most of the Lower

Bathyal Zone (Fig. 13).

Krithe sp. 22

Figs 17Q-R, 18K, 22D

Illustrated material

MF-0448, RV, TBD 6851, 2 916 m.

MF-0458, LV, TBD 6851, 2 916 m.

Remarks

A small species with a gently rounded DM outline in lateral view. Its

overall shape is very similar to that of Krithe capensis and the two have similar

length/height ratios (Krithe sp. 22 = 1,93; Krithe capensis = 1,86). However, the

great difference in size between the two species facilitates identification

(Fig. 20). Internally, the two species differ in shape of the vestibule; in Krithe

sp. 22 it is small, with a short, straight, inner margin post-adjacent to it.

Krithe sp. 22 is a rare abyssal form that we encountered only in sample 6851

(2 916 m), where it constitutes 12 per cent of the total Krithe population.

_ AN

DEEP-WATER QUATERNARY OSTRACODA 285

ose

Se AE

Bee,

Fig. 23. A. Krithe sp. 7, SAM—PQ-MF-0446, RV, TBD 6851, 2 916m. B. Krithe sp. 19,

SAM-—PQ-MF-0447, RV, TBD 6851, 2 916m. C. Krithe sp. 9, SAM—PQ-—MF-—0443, RV,

TBD 3524, 475m. D. Parakrithe sp. 10, SAM-—PQ-MF-0449, RV, TBD 3553, 1 003 m.

E-F. Buntonia rosenfeldi sp. nov. TBD 3338, 990 m. E. SAM—PQ-MF-—0460, LV, SEM 2799.

F. SAM—PQ-MF-0459, holotype, RV, SEM 2792. Scale bars = 100 microns.

286 ANNALS OF THE SOUTH AFRICAN MUSEUM

Genus Parakrithe van den Bold, 1958a

Parakrithe sp. 10

Figs 171, 18B, 23D

Illustrated material

MF-0449, RV, TBD 3553, 1 003 m.

Remarks

This relatively large (0,72 mm) species has a slight bulge on the antero-

dorsal margin in lateral view, and a less pointed postero-ventral outline than in

most of the examples discussed by Peypouquet (1979). The anterior vestibule is

relatively large and widens anteriorly. We place it within Peypouquet’s (1979)

ecotype A3. Van den Bold (1966) illustrated three species of the genus from the

Miocene of Gabon (P. robusta sp. nov., P. datylomorpha Ruggieri, 1962, and

P. vermunti (van den Bold, 1946)), but none are conspecific with our species.

Off south-western Africa, Parakrithe sp.10 has a depth range of

900-1 353 m, which limits it to the portion of the AAIW that lies between the

base of the Salinity Minimum Zone, and the top of the NADW mass.

Family Buntoniidae Apostolescu, 1961

Genus Buntonia Howe, 1935 (in Howe & Chambers, 1935)

Ruggieri (1958) split the genus Buntonia and separated off the large, rela-

tively thin-shelled and smooth taxa into Quasibuntonia. Van Morkhoven (1963)

did not accept this as taxonomically valid, and we follow his example. However,

the forms that were represented in Ruggieri’s Quasibuntonia certainly constitute

a geographically well-defined group: they inhabit relatively deep water, and are

(and were) confined to areas adjacent to Africa, and in the Mediterranean

(Benson & Sylvester-Bradley 1971). Representatives of Buntonias.s. have a

world-wide distribution at all water depths.

The genus Buntonia is an important component of the ostracod populations

off south-western Africa, where five species occur over a latitudinal range 17°S

to 35°S, in water depths of 95-2 070 m (Fig. 24). All five species are found in

the Neritic Zone, where mean values of the genus’s abundance within the ostra-

cod population (in samples that contain the genus) are 9,8 per cent (range

0,1-66%). Only two species (B. rosenfeldi sp. nov. and Buntonia sp. 34) extend

beyond the continental shelf on to the slope, and only B. rosenfeldi sp. nov.

occurs in the Bathyal Zone. The latter species belongs in the group Quasibunto-

nia, as understood by Ruggieri (1958) and Benson & Sylvester-Bradley (1971).

We did not find the genus in the Abyssal Zone.

Despite the reduction in diversity of the genus into progressively deeper

water, mean values of abundance in the Bathyal Zone are higher than in

shallow-water areas: 30 per cent (range 3-100%). A three-point running mean

DEEP-WATER QUATERNARY OSTRACODA 287

water depth, km

latitude °S

@- B.rosenfeldi

™@— modern specimens

Fig. 24. Latitude and water depth of samples bearing Buntonia spp. Solid points and outline

indicate the distribution of Buntonia rosenfeldi sp. nov.

plot of the percentage of all Buntonia species within the overall ostracod popu-

lations from all our samples off south-western Africa (Fig. 25) shows a general

increase in abundance of the genus from the inner shelf to the lower part of the

Neritic Zone (i.e. 95—900 m). We detect three populations within these shallow-

water assemblages but will defer further discussion to a later publication. At the

Neritic/Bathyal boundary (c. 950 m), there is fluctuation at the apex of the

curve, which peaks at around 25 per cent of the overall ostracod population.

Below this depth, in the Upper Bathyal Zone, values fall steadily for about

250 m. Clearly, there is an important physio-chemical barrier at around 950 m

that has the following effects: (a) the disappearance of Buntonia sp. 34; (b) a

reduction in the relative size of the population of B. rosenfeldi sp. nov.

Buntonia rosenfeldi sp. nov. is the only bathyal species of the genus,

although valves of Buntonia sp. 34 occur as deep as 1 050 m. Mean values of

percentage of the ostracod population show a high in the Upper Bathyal Zone

compared to the Lower Bathyal Zone (35%, range 6—-100%; 20%, range

3—40%, respectively), but these figures hide the true distribution, which is

closely linked to the boundary zones of the water masses. We will discuss this

under ‘Remarks’ on B. rosenfeldi sp. nov.

288 ANNALS OF THE SOUTH AFRICAN MUSEUM

Peypouquet & Benson (1980) recorded the genus (as Quasibuntonia spp.)

from their transects in the Cape and Angola basins. There are too few data

points on their curves to make a detailed comparison with our results (cf.

Figs 25, 26), but they suggest a decline from high values of percentage of overall

ostracod populations in shallow water (20% in 450 m) to a low of 1 per cent at

around 1 000 m. They recorded three sites with relatively high values (20-30%)

in depths that we classify as Lower Bathyal/uppermost Abyssal, and a deeper

site (2 800 m) at 6 per cent. These data are broadly compatible with our results,

but we suspect that they are too scattered to resolve the actual distribution.

Benson & Sylvester-Bradley (1971) discussed the distribution of the related,

relatively large species, B. sulcifera (Brady, 1887) and _ B. radiatopora

(Seguenza, 1880), and concluded that these deep-water buntoniids represent the

remnants of a “Tethyan’ fauna that is restricted to a circum-Africa zone.

t+— B. sp. 72

UPPER LOWER

NERITIC BATHYAL BATHYAL

mean % =9:°8 mean % = 35 mean % = 20

% Buntonia spp.

jo)

water depth, km

Fig. 25. Buntonia species as percentage of total ostracod fauna plotted against water depth.

Values are five point running means. Depth ranges for all Buntonia species on the continental

margin are shown by bars. Mean % = mean percentages of Buntonia species in total ostracod

fauna for each depth zone.

DEEP-WATER QUATERNARY OSTRACODA 289

30 NERITIC BATHYAL ABYSSAL

UPPER LOWER

(oe)

% Buntonia spp.

fo)

{ 2 3

water depth, km

Fig. 26. Buntonia species as percentage of total ostracod fauna plotted against water depth for a

profile off Walvis Bay. Data computed from Peypouquet & Benson (1980).

Neither Cronin (1983) nor Benson et al. (1983) recorded taxa from the con-

tinental margin of eastern North America that would fall into the category

Quasibuntonia.

Buntonia rosenfeldi sp. nov.

Figs 23E-F, 27A—D

Buntonia sulcifera? (Brady, 1887) Rosenfeld & Bein, 1978: 18, pl. 1 (fig. 21).

Buntonia sp. 1 Boomer, 1985: 34-35, pl. 2 (figs 27-28). (These are probably all juveniles.)

Buntonia sp. 2 Boomer, 1985: 35-36, pl. 2 (figs 33-34). (These are probably all adults.)

Derivation of name

The species is named for Dr A. Rosenfeld (Geological Survey of Israel) for

his work on deep-water ostracods from north-western Africa.

Holotype

MF-0459, RV, TBD 3338, 990 m.

Paratypes

MF-0460, LV, TBD 3338, 990 m.

MF-0461, LV, TBD 3338, 990 m.

MF-0462, RV, TBD 3109, 900 m.

290 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 27. A-D. Buntonia rosenfeldi sp. nov. A-C. TBD 3338, 990 m. A. SAM-—PQ-MF-0459,

holotype, LV seta, SEM 2793. B. SAM-—PQ-—MF-0461, LV internal view, SEM 2795.

C. SAM-PQ-MF-0461, LV, MS, SEM 2796. D. SAM-—PQ-MF-0462, RV, TBD 3109, 900 m,

SEM 2790. E-F. Dutoitella suhmi (Brady 1880), TBD 6851, 2 916 m. E. SAM—PQ-MF-0463,

LV, SEM 2936. F. SAM—PQ-MF-—0464, RV, SEM 2940. Scale bars: A = 10 microns;

C-F = 100 microns.

DEEP-WATER QUATERNARY OSTRACODA 291

Diagnosis

Species with well-developed longitudinal ventro-lateral keel and reticulate

ornamentation in posterior part of lateral valve surface.

Description

Typical ovate buntoniid in lateral outline with broadly rounded AM and

narrow, bluntly truncated PM. High, arched DM that has an abrupt step to the

PM in LV, but is continuous with PM outline in RV. VM is straight or slightly

concave. There is a prominent, keeled, ventro-lateral ridge that passes

anteriorly into a faint rib running parallel to the AM. AM area is strongly

compressed. Posterior lateral surface is reticulate, with indistinct longitudinal

ribbing and prominent conjugate pores. Anterior valve surface is faintly reticu-

late, with a delicate tracery of muri and inter-mural pitting.

Hinge is amphidont, with both ATE in LV open ventrally. There are

narrow anterior vestibules. MS consist of four adductors, the ventral and dorsal

of which are ovate, and a hooked anterior scar, above which lie two small

rounded scars.

Dimensions (mm)

length height

ME-0459 0,66 0,43

MF-—0460 0,69 0,45

MF-0461 0,68 0,46

MF-0462 0,67 0,44

Remarks

Three species are closely related to B. rosenfeldi sp. nov.: B. radiatopora

(Seguenza, 1880), B. pyriformis (Brady, 1880), and B. sulcifera (Brady, 1887).

The closest is B. radiatopora (Seguenza, 1880) from the Neogene of south-

ern Italy. Seguenza (1880) recognized two varieties, but stated that there is a

continuous transition between them and that he was unable to differentiate

separate species. Buntonia radiatopora radiatopora has longitudinal ridges in the

posterior half of the valves, whereas the variety B. r. sculpta has ridges over the

whole valve surface. The former variety has been illustrated by Benson &

Sylvester-Bradley (1971), and both varieties by Colalongo (1965). Buntonia

rosenfeldi sp. nov. differs from B. radiatopora (Seguenza) in having reticulate

ornamentation in the posterior half of the valve.

Buntonia sulcifera (Brady, 1887) is very close to B. radiatopora (Seguenza),

because both species possess ornamentation of longitudinal ribs in the posterior

half of the valve. They may be conspecific, although the rib pattern in the

former may be sharper if the illustration by Benson & Sylvester-Bradley (1971)

of a specimen from the Mozambique Channel is the same species as Brady’s.

Whatever the case, B. rosenfeldi differs from B. sulcifera by lacking the longi-

tudinal median ribs in the posterior half of the valve.

292 ANNALS OF THE SOUTH AFRICAN MUSEUM

Buntonia pyriformis (= B. mackenziei nom. nov. Puri & Hulings, 1976) has

a similar outline to B. rosenfeldi but is more elongate, has a smooth lateral valve

surface (Brady 1880: 78), and an eyespot (Puri & Hulings 1976: 281).

Buntonia rosenfeldi sp. nov. occurs over a depth range of 186-2 070 m off

south-western Africa, and 1 418-2 859 m off north-western Africa (recorded as

B. sulcifera? by Rosenfeld & Bein 1978, fig. 21). Buntonia radiatopora is

reported as living at 2 816 m in the eastern Mediterranean and fossil in the

Plio—Pleistocene of southern Italy and Sicily (Benson & Sylvester-Bradley

1971). Buntonia sulcifera (Brady, 1887) was recorded by Brady (1887) from

3 655 m off Mauritius, and 2 980 m from the Mozambique Channel by Benson

& Sylvester-Bradley (1971), and B. pyriformis (Brady, 1880) was first recorded

in 675 fm (1 234 m) off Brazil (Brady 1880—‘Challenger’ site 120), and has

been found between 400 m and 830 m off north-western Africa by Rosenfeld &

Bein (1978). Buntonia cf. B. pyriformis (Brady) (recorded as cf. B. mackenziei

Puri & Hulings) has been reported from late Miocene and late Pliocene strata at

DSDP site 608 in the North Atlantic by Whatley & Coles (1987).

Figure 28 shows the abundance of Buntonia rosenfeldi sp. nov. across its

depth range off south-western Africa. In the Neritic Zone it constitutes a mean

| |

NERITIC ! BATHYAL :

! UPPER | LOWER

mean %=6:°5 mean % = 29 mean % = 20

% Buntonia rosenfeldi

0:5 1-0 1:5 2:0

water depth, km

Fig. 28. Buntonia rosenfeldi sp. nov. as percentage of total ostracod fauna plotted against water

depth. Values have not been smoothed.

DEEP-WATER QUATERNARY OSTRACODA 293

of 6,5 per cent (range 1-25%) the ostracod population (in samples in which it

occurs) and, for depths shallower than approximately 900 m, there are few

samples with values above 10 per cent, although there is a slow, progressive

increase with depth. Within the Bathyal Zone (i.e. 950—2 070 m), the mean

abundance of B. rosenfeldi is 27 per cent (range 1-100%), so that it appears to

represent a characteristic element of the deep-water fauna. However, it is at

water mass boundaries that the species is most successful in establishing itself: at

the Neritic/Upper Bathyal boundary values are c. 20 per cent, and at the Upper/

Lower Bathyal boundary values are over 35 per cent. Nevertheless, we did not

record it from the Abyssal Zone, and values in the Lower Bathyal Zone steadily

decline below about 1 600 m. From these data we conclude that B. rosenfeldi

prefers relatively cold, saline water, and that it is particularly successful, in

comparison with other ostracod species, at tolerating the unstable conditions

that occur at the major water mass boundaries (i.e. at the base of the AAITW

low salinity zone, and the AAIW/NADW shear zone). It cannot tolerate the

adverse conditions of the AABW.

Family Trachyleberididae Sylvester-Bradley, 1948

Subfamily Unicapellinae Dingle, 1981

Genus Dutoitella Dingle, 1981

Recognition of this genus in Quaternary deep-sea sediments in the south-

eastern Atlantic necessitates expansion of the concept of this genus to include

reticulate species. This in turn allows the accommodation within Dutoitella of

several species of previously uncertain affinity: D. eocenica (Benson, 1977) from

the South Atlantic, ‘Suhmicythere’ sp. Benson et al., 1983, from the north-

western Atlantic, and D. crassinodosa (Guernet, 1985) from the Indian Ocean.

Phylogenetic implications of these new data are that, between Maastrichtian and

Eocene times, the genus migrated from south-eastern African outer continental-

shelf environments into deeper-water habitats on both sides of the South

Atlantic and in the Indian Ocean. There was a concomitant development of

reticulation.

A similar trend can be seen in Aflanticythere, with spinose species appearing

by Eocene times. Architectural similarity between the two genera strongly sug-

gests a common ancestor (Fig. 29).

Dutoitella suhmi (Brady, 1880)

Figs 27E-F, 30A-B, 31A, C, F

Cythere suhmi Brady, 1880: 106-107, pl. 26 (fig. 3a—h). Puri & Hulings, 1976: 290-291, pl. 17

(figs 7-12), text-fig. 10.

‘Suhmicythere’ suhmi (Brady, 1880): Whatley & Coles, 1987, pl. 6 (figs 18-21).

‘Suhmicythere’ sp. Benson et al., 1983, pl. 1 (fig. 8).

294 ANNALS OF THE SOUTH AFRICAN MUSEUM

MIO PLI QUA

Dutoitella

* mimica' $ eocenica2® *# suhmi*®

* sp. indet.®

* crassinodosa’

* dutoiti'

Atlanticythere

*~ maestrichtia2 * murareticulata2

* prethallasia?

Uncertain affinity

~ carlitae®

* = eastern Atlantic Ocean

$ = western Atlantic Ocean

# = north-western Atlantic Ocean

* = Indian Ocean

sn--=-=- = known range

Saeae = assumed range

'= Dingle 1981; * = Benson 1977; ° = Frewin 1987; ¢ = Brady 1880; ° = Benson &

Peypouquet 1983; ® = Benson et a/. 1983; ” = Guernet 1985; ® = Peypouquet & Benson

1980 (= ‘Shumicythere’ [sic]); 9 = Miocene record originally designated Atlanticythere?

neogenica by Benson (1977).

Fig. 29. Geological ranges of modern and fossil species of Dutoitella and Atlanticythere from the

Atlantic and Indian oceans.

Illustrated specimens

MF-—0463, LV, TBD 6851, 2 916 m.

MF-0464, RV, TBD 6851, 2 916 m.

MF-0465, RV, TBD 6851, 2 916 m.

MF-0466, LV, TBD 6851, 2 916 m.

Remarks

The species, first described by Brady (1880) from the north-western Pacific

and Prince Edward Island (Southern Ocean) as Cythere suhmi Brady, 1880, is

externally similar to the type species of Dutoitella, having the typical lateral

DEEP-WATER QUATERNARY OSTRACODA 295

Fig. 30. A-B. Dutoitella suhmi (Brady, 1880), TBD 6851, 2 916 m. A. SAM—PQ-MF-0465,

RV internal view, SEM 2942. B. SAM—-PO-MEF-0466, LV internal view, SEM 2938. C-F.

Abyssocythere australis Benson, 1971, TBD 6851, 2916m. C. SAM-—PQ-—MF-0467, LV,

SEM 2946. D. SAM—PQ-MF-0468, RV, SEM 2960. E. SAM—PQ-MF-0469, LV internal

view, SEM 2948. F. SAM—PO-MF-0470, RV internal view, SEM 2957.

Scale bars = 100 microns.

296 ANNALS OF THE SOUTH AFRICAN MUSEUM

2) QD

or £4

Fig. 31. Comparative morphology of various species of Dutoitella. A. D. suhmi (Brady 1880),

SAM-PQ-MF-—0464, RV, TBD 6851, 2 916m, SEM 2940. B. D. mimica Dingle, 1981,

SAM-K5748, RV, TBD 818, Alphard Formation, Agulhas Bank, Maastrichtian III.

C. D. suhmi (Brady 1880), SAM-PQ-MF-0463, LV, TBD 6851, 2 916m, SEM 2936.

D. D. neogenica (Benson 1977), USNM 190300, LV, DSDP site 22, Lower Miocene, from

Benson (1977, pl. 1 (fig. 8)). E. ‘Suhmicythere’ sp., USNM 247710, 3000 m off New-

foundland, Quaternary, from Benson et al. (1983, pl. 1 (fig. 8)); is probably conspecific

with D. suhmi (Brady, 1880). F. MS of D. suhmi (Brady, 1880), SAM—PQ-MF-0465, RV,

TBD 6851, 2 916m, SEM 2944. G. MS of D. mimica Dingle, 1981, SAM-K5449, LV,

TBD 818, Alphard Formation, Agulhas Bank, Maastrichtian III. Scale bars = 100 microns.

outline, with contrasting eared LV and stepped RV antero-dorsal outline, of the

Cretaceous (Campanian—Maastrichtian) type species (D. dutoiti Dingle, 1981).

Its MS pattern is very similar to that of D. mimica Dingle, 1981 (Santonian—

Maastrichtian). Dutoitella suhmi (Brady) differs from both Cretaceous species in

being reticulate, having a less prominent SCT, and having the lateral ridge or

node post-adjacent to the SCT replaced by three short, indistinct ribs. With the

exception of the reticulation, the surface architecture, including location of pore

conuli and dorsal margin spines of D. suhmi (Brady) and D. mimica, is very

similar (Fig. 31). The internal features of these two species are also very close,

the major difference being that the LV PTE of D. suhmi lies in a slightly more

postero-ventral position.

DEEP-WATER QUATERNARY OSTRACODA 297

The illustrations of Puri & Hulings (1976: 290-291, pl. 17 (figs 7-12), text-

fig. 10) of lectotypes of D. suhmi (Brady) show a slightly different MS pattern to

our specimens of both D. suhmi (Brady) and D. mimica Dingle, 1981. The

former show four non-divided adductors, whereas our specimens have a sub-

divided second adductor. R. C. Whatley (pers. comm. 1988) informs us, how-

ever, that this variation in D. suhmi is within the range that he has observed for

the species worldwide, and appears to have no taxonomic significance.

Brady (1880) reported Cythere suhmi from water depths of 100-4 600 m,

and Whatley & Coles (1987) have found it in deep-water (>3 000 m) Miocene—

Quaternary sediments of the North Atlantic. Dutoitella suhmi (Brady, 1880) is

known from site TBD 6851 within the Abyssal Zone (2 916 m) of the Cape

Basin, where it forms 6 per cent of the ostracod fauna.

Benson et al.’s (1983) record of ‘Suhmicythere’ sp. from 3 000 m on the con-

tinental slope off Newfoundland also probably refers to this species, and it is

possible that Peypouquet & Benson’s (1980) citation of “‘Shumicythere’ [sic] from

a range of 3 797-4595 m in the Angola Basin at least refers to species of

Dutoitella. Benson (1977) listed ‘Suhmicythere’ sp. from late and mid-Miocene

horizons at DSDP site 357 on the Rio Grande Rise, but did not illustrate

the material. These may, therefore, also be records of reticulate species of

Dutoitella.

When he originally erected the two species Atlanticythere? eocenica Benson

and A.? neogenica Benson, Benson (1977: 877) queried their generic assign-

ment: “This species [A.? eocenica] and A.? neogenica Benson, n. sp. may be

considered later as generically distinct [from other species of Atlanticythere].’

The continuous AM and ventro-lateral ridge indicates that Benson’s species

belong in Dutoitella. In addition, we consider that these two species are conspe-

cific and, in revision, designate D. eocenica (Benson, 1977) to be the valid

taxon, because it is described earlier in the publication (i.e. D. neogenica

(Benson, 1977) is a junior synonym of D. eocenica (Benson, 1977)).

The species D. eocenica (Benson, 1977) and D. suhmi (Brady) have very

similar patterns of surface reticulation, with the main points of difference being

in the routes of the reticulation muri adjacent to the AM, and the presence of a

short ridge post-adjacent to the SCT in D. eocenica compared to three narrow

ribs in D. suhmi. In this latter feature, D. eocenica is close to the Cretaceous

species of the genus (Fig. 31).

We also refer ‘Cythereis’ crassinodosa Guernet, 1985, to Dutoitella and con-

sider it to be another close relative of D. suhmi. Guernet (1985) compared his

species generically to ‘Suhmicythere’ sp. Benson et al., 1983, and recorded it

from bathyal assemblages of early (Ypresian) to late (Priabonian) Eocene age at

DSDP site 214 (Chagos Ridge). He also mentioned ‘C.’ aff. C. crassinodosa

from the Lower Eocene at DSDP site 245 (Madagascar Basin, south-western

Indian Ocean), and ‘C.’ cf. C. crassinodosa from the middle Eocene at DSDP

site 214 on the central 90 East Ridge. Dutoitella crassinodosa (Guernet, 1985)

298 ANNALS OF THE SOUTH AFRICAN MUSEUM

differs from D. suhmi (Brady) in having a more prominent SCT and prominent

nodes on its DM and VM.

Phylogenetic implications of our new data are summarized in Figure 29 and

suggest that in the early Tertiary, D. mimica migrated from its preferred habi-

tats on the outer continental shelf (?100—200 m water depths—see Dingle 1981,

1985) and colonized deep-water sites in the western South Atlantic and in the

south-western, north-western and central Indian Ocean. During the course of

this, mutation into at least two species occurred: D. eocenica (Eocene—Miocene)

and D. crassinodosa (Eocene). Subsequent development produced D. suhmi

(Miocene—Quaternary) and possibly other species that have been recorded as

‘Suhmicythere’ (e.g. Benson 1977; Peypouquet & Benson 1980).

At this stage it is premature to speculate on possible links between

Dutoitella and Atlanticythere but, if the latter did evolve from the former, then

the main architectural modifications necessary before Maastrichtian time were

the re-organization of the route of the AM and ventro-lateral ridges, a reduction

in the size of the SCT and post-adjacent nodes and ridges, and a general

increase in valve size. So far, the only record of the genus Aflanticythere in the

eastern South Atlantic is Aftlanticythere sp. BO58 from the Eocene of the

Agulhas Bank (Frewin 1987).

Neither Rosenfeld & Bein (1978) nor Cronin (1983), in their studies of

deep-water faunas, referred species to the genera Dutoitella, Atlanticythere, or

‘Suhmicythere’ .

Subfamily Trachyleberidinae Sylvester-Bradley, 1948

Genus Abyssocythere Benson, 1971

Abyssocythere australis Benson, 1971

Figs 30C-F, 32A

Abyssocythere australis Benson, 1971: 18, pl. 3 (fig. 7), text-fig. 12.

Illustrated specimens

MF-0467, LV, TBD 6851, 2 916 m.

MF-0468, RV, TBD 6851, 2 916 m.

MF-0469, LV, TBD 6851, 2 916 m.

MF-0470, RV, TBD 6851, 2 916 m.

Remarks

Externally, the specimens from off south-western Africa differ from those

off southern Australia only by possessing a slightly weaker AM rim. In his orig-

inal description of A. australis, Benson (1971) did not give details of the internal

features of the species, but we can report that the MS pattern (Fig. 32) is similar

to that of the type species A. casca Benson, 1971. Also, the hinges of the two

DEEP-WATER QUATERNARY OSTRACODA uS)

Fig. 32. MS of Abyssocythere. A. A. australis Benson, 1971, SAM-PQ-MF-0470, RV,

TBD 6851, 2 916 m , SEM 2958. Scale bar = 100 microns. B. A. casca Benson, 1971, no local-

ity given, c. 3 000 m, off Madagascar (from Benson 1971, fig. 6). No scale given.

Species are similar but, in comparison with A. casca, our material exhibits a

weaker ATE in the RV, where the anterior tooth is more elongate and in lateral

view projects above the valve margin at the ACA. In addition, the socket at the

anterior end of the narrow ME groove is small and does not project below the

general line of the hinge, as occurs in A. casca.

When he originally proposed the genus, Benson (1971) recorded six species

of Abyssocythere, all of which had modern representatives. Subsequently, four

more have been reported in the literature, with the result that ten separate

species are now known, six of which have a fossil record that ranges Eocene to

Recent (Table 3).

Figure 33 shows the distribution of the Quaternary species of Abyssocythere.

Our new data pose an interesting problem in that the geographical range of

A. australis can now be extended across the Southern Ocean into the Cape

Basin, but that the range of A. casca seems to be limited to the northern

Mozambique/Somali basins. The species have overlapping depth ranges

(Table 3), so presumably there is a physico-chemical barrier to the migration of

A. casca southward through the deep-water passages into the Cape Basin,

although the nature of this barrier is not obvious, particularly in view of the fact

that another of the typical Abyssal Zone taxa (Poseidonamicus major) does

extend from the Mozambique Basin into the South Atlantic.

This species is a characteristic element of the Abyssal Zone ostracod

assemblage. Our specimens were recovered from a single station (TBD 6851) at

2 916 m, where Abyssocythere australis constituted 6 per cent (23 valves) of the

total ostracod fauna, with 17 per cent of the specimens considered modern. At

the only previously known site (3 390 m, south of Australia), none of the speci-

mens were modern (i.e. they were ‘relict’, presumably Pleistocene) (Benson

1971).

No representatives of the genus Abyssocythere were recovered from the

deep-water surveys of Rosenfeld & Bein (1978), Peypouquet & Benson (1980),

Benson et al. (1983), and Cronin (1983).

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ANNALS OF THE SOUTH AFRICAN MUSEUM

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DEEP-WATER QUATERNARY OSTRACODA 301

inal

Fig. 33. Distribution of modern species of Abyssocythere. Re-plotted from data in Benson

(1971—dots), with sample site TBD 6851 off south-western Africa shown as an open circle.

Genus Ambocythere van den Bold, 19586

A listing of Recent species of this genus that have previously been described

from relatively deep water, shows that the genus Ambocythere has a depth range

from the inner continental shelf to the Abyssal Zone:

Bathyal/Abyssal

A. ramosa—lIceland, c. 1000 m (Van den Bold 1965); Newfoundland,

2 938-3 210 m (Benson et al. 1983).

Ambocythere cf. A. ramosa—north Atlantic, 2 445m (DSDP site 610,

Whatley & Coles 1987).

Ambocythere sp. 3057—south-eastern Atlantic, 2 070 m (present study).

Ambocythere caudata—Iceland, c. 1 000 m (Van den Bold 1965).

Neritic

Ambocythere keiji— Venezuela, continental shelf (Van den Bold 1958b)

Ambocythere stolonifera—False Bay, South Africa, 30-40 m (Brady 1880)

Ambocythere spp. A, B, and C—south-eastern USA, 261-1 034 m (Cronin

1983).

302 ANNALS OF THE SOUTH AFRICAN MUSEUM

Including fossil records, the genus has a Neogene range that includes the

Caribbean, North and South Atlantic, Indonesia, Japan, Australia, and South

Africa (Van den Bold 1965; Benson 1983).

Ambocythere sp. 3057

Figs 34A, 35A

Illustrated specimen

MF-0471, LV, TBD 3355, 2 070 m.

Remarks

This is a new species, but we have insufficient material (2 juveniles) to

warrant a formal description. It was originally noted (but not described or illus-

trated) by Boomer (1985: 66) as Ambocythere cf. A. stolonifera, but its closest

relative is A. subreticulata van den Bold, 19585, from the Oligocene—Miocene of

the Caribbean. Ambocythere sp. 3057 and A. subreticulata differ in the pattern

and number of lateral ribs: A. subreticulata has numerous small riblets in the

ventro-lateral area. Ambocythere stolonifera (Brady, 1880) from False Bay has a

similar lateral outline and main rib arrangement to Ambocythere sp. 3057, but is

more elongate and has several small ancillary riblets between the main dorsal

and median ribs. The two other known deep-water species differ in the following

points: A. ramosa is elongate, with numerous fine longitudinal ribs and a

VM-AM-DM rim that is complete; A. caudata is also more elongate and has a

marked re-entrant on the postero-ventral margin.

Ambocythere sp. 3057 is a rare species that has been recorded only from the

Lower Bathyal/Abyssal Zone boundary off south-western Africa (TBD 3355,

2 070 m), where it constitutes 7 per cent of the total ostracod fauna. This value

compares to a mean of 8,5 per cent of the total ostracod fauna at the two abyssal

sites off Newfoundland for Ambocythere ramosa (Benson et al. 1983).

The wide sector of continental margin off south-western Africa that separ-

ates the sample site with Ambocythere sp. 3057 from the False Bay population

of Ambocythere stolonifera, recorded by Brady (1880), is devoid of any record

of the genus, so it is reasonble to assume that the deep- and shallow-water popu-

lations of Ambocythere in this region have a long history of genetic isolation.

The only known possible record of the genus in the Tertiary of southern Africa

is from the Agulhas Bank (TBD 819; Middle Eocene—Middle Oligocene), where

Frewin’s (1987) Indeterminate Genus 10 sp. B298 bears some resemblance to

A. stolonifera.

Genus Echinocythereis Puri, 1954

This genus is distinguished from Henryhowella primarily on the possession

of a split anterior MS. On this basis, the taxonomic position of several species

DEEP-WATER QUATERNARY OSTRACODA 303

—~_——""’

a arc no cae RUNES DOTS)

Fig. 34. Outlines of various species of Ambocythere. A. Ambocythere sp. 3057,

SAM-PQ-MF-0471, LV, TBD 3355, 2070 m. B. A. subreticulata van den Bold, 1958b,

Miocene, Cuba (from Van den Bold 19586, fig. 15). C. A. stolonifera (Brady, 1880),

‘Challenger’ station 140, 15-20 fm, False Bay (from Brady 1880, pl. 21 (fig. 3a)). D. A. ramosa

van den Bold, 1965, USNM 342104, 1 400 m off Newfoundland (from Benson et al. 1983, pl. 2

(fig. 1)). E. A. caudata van den Bold, 1965, HVH-7897, holotype, c. 1 000 m off Iceland (from

Van den Bold 1965, pl. 1 (fig. 12)). Scale bar = 100 microns.

similar to the material available to us has been clarified by the re-illustration of

Brady’s (1880) ‘Challenger’ ostracods by Puri & Hulings (1976) (Table 4).

Echinocythereis whatleyi sp. nov.

Figs 35B-F, 36E-G, I-J

‘Xandarosina’ sp. Boomer, 1985: 64, fig. 7.

Echinocythereis echinata (non Sars, 1866) Benson et al., 1983, pl. 2 (fig. 8).

Derivation of name

This species is named for Professor R. C. Whatley (University College of

Wales, Aberystwyth) for his work on deep-water ostracod faunas.

304 ANNALS OF THE SOUTH AFRICAN MUSEUM

TABLE 4

Previously-described species allocated to Echinocythereis

and Henryhowella on the basis of the central muscle-scar

pattern, following the revision of Puri & Hulings (1976).

A _ Split anterior muscle scar

Genus Echinocythereis

Cythere irpex Brady, 1880

Cythereis echinata Sars, 1866

B Single, hooked anterior muscle scar

Genus Henryhowella

Cythere circumdentata Brady, 1880

Cythere melobesioides Brady, 1869

Cythere ericea Brady, 1880

Cythere dasyderma Brady, 1880

Holotype

MF-0472, RV, TBD 3821, 1 525 m.

Paratypes

MF-0473, LV, TBD 6851, 2 916 m.

MF-0474, LV, TBD 3109, 900 m.

MF-0475, RV, TBD 3177, 1 000 m.

Diagnosis

Plump, blind species with broadly rounded AM and PM, and delicate

surface ornamentation of small spines and lace-like reticulation.

Description

The species has a relatively delicate shell with broadly rounded AM and

narrower rounded PM, more acuminate in RV. DM is short and straight, VM

slightly concave. Antero-dorsal areas are somewhat compressed. Central valve

area is plump, with the ‘belly’ of the lateral area just reaching to the VM.

Highest point of the valve is over the ACA. No eyespots or ocular sinus. Valve

surface is covered in fine spines arranged concentrically, being larger and more

numerous postero-ventrally. Surface covered in a very fine, lace-like recticula-

tion. AM has two, closely parallel rows of fine spines.

In internal view, marginal areas are narrow, with no vestibules. Hinge is

weak, modified amphidont, with dorsally open terminal elements in LV. All

elements appear smooth. MS consist of four elongate adductors, the second

scar being the largest, with two small rounded anterior scars.

DEEP-WATER QUATERNARY OSTRACODA 305

Fig. 35. A. Ambocythere sp. 3057, SAM—PQ-MF-0471, LV, TBD 3355, 2 070 m, SEM 3058.

B-F. Echinocythereis whatleyi sp. nov. B. SAM—PQ-—MF-0472, holotype, RV, TBD 3821,

1525 m. C. SAM—-PQ-MF-0473, LV internal view, TBD 6851, 2 916m. D. SAM-—PQ-

MF-0474, LV, TBD 3109, 900 m. E. SAM—PQ-MF-0475, RV dorsal view, TBD 3177,

1 000 m. F. SAM—-PQ-MF-0472, holotype, RV internal view, TBD 3821, 1 525 m.

Scale bars = 100 microns.

306 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 36. Outlines of Echinocythereis. A, H. E. echinata (Sars, 1866). A. LV. H. Dorsal view.

From Sars (1928, pl. 90). Localities unknown. B, D. E. echinata (Sars, 1866). B. DSDP

site 611D-12 c.c. Pliocene. D. DSDP site 611D-1 c.c. Quaternary, NE Atlantic. From

Whatley & Coles (1987, pl. 5 (figs 7-8)). C. E. echinata (Sars, 1866), specimen 13290, 2859,

Quaternary, 2 859m off NW Africa. From Rosenfeld & Bein (1978, pl.1 (fig. 17)).

E. E. whatleyi sp. nov. USNM 342109, station 77034-15, Quaternary, 3 000m off New-

foundland. From Benson et al. (1983, pl.2 (fig.8)). F. E. whatleyi sp. nov. Holotype,

SAM-PQ-MF-0472, TBD 3821, 1525m. G. E. whatleyi sp. nov., SAM-—PQ-MF-0474,

TBD 3109, 900m. I. E. whatleyi sp.nov., SAM-PQ-MF-0475, TBD 3177, 1000 m.

J. E. whatleyi sp. nov., SAM—PQ-—MF-0473, MS, LV, TBD 6851, 2916m. Scale bars:

B-I = 100 microns; J = 30 microns; A, H = scales unknown.

DEEP-WATER QUATERNARY OSTRACODA 307

Dimensions (mm)

length height

MF-0472 0,56 0,39

MF-0473 0,51 0,38

MF-—0474 0,46 O33

Remarks

Echinocythereis whatleyi sp. nov. is closely related to Echinocythereis

echinata (Sars, 1866) and E. irpex (Brady, 1880). Sars (1928) considered

E. irpex to be synonymous with E. echinata, and certainly these two species are

more similar in lateral outline to each other than either is to E. whatleyi.

Echinocythereis whatleyi differs from both these species in having a

plumper, less quadrate outline in lateral view. In particular, it has a shorter DM,

with a less pronounced angle in the postero-dorsal region, and a more

pronounced, rounded VM ‘belly’. In addition, the degree of compression

of the anterior marginal area in E. whatleyi is moderately strong in comparison

to E. echinata (see dorsal views), and there is a difference in the shape of the

postero-ventral and PM outlines, which are rounded and swept dorsally in

E. whatleyi and ‘obtusely blunted’ in E. echinata (Sars 1928). Both E. echinata

and EF. irpex have a spinose ventro-lateral keel that is strongest posteriorly. This

feature is lacking in E. whatleyi sp. nov.

Other species that have some similarities to Echinocythereis whatleyi are:

E. jacksonensis (Howe & Pyeatt, 1935, in Howe & Chambers, 1935) from the

Middle Eocene to Oligocene of south-eastern USA and the Caribbean (which is

more elongate, and is sighted—see Howe & Howe 1973); E. madremaestrae van

den Bold, 1988, from the Upper Miocene to Pliocene of the Caribbean (which

has a very similar outline and ornamentation, but possesses a prominent eye

tubercle); and a specimen referred to E. irpex (Brady) by Sylvester-Bradley &

Benson (1971, fig. 24), which has two strong, short, antero-ventral ridges, and a

denser overall covering of spines than our species.

Van den Bold (1966) described a new species of Echinocythereis from the

Miocene of Gabon, but this taxon (E. ecphyma) has a hooked anterior MS, and

consequently belongs to another genus.

Echinocythereis echinata (Sars) has been widely reported from the North

Atlantic and the Mediterranean by numerous authors, in depths ranging from

60-600 m off Norway (Sars 1928: 195) to 4 700m in the Central Atlantic

(Tressler 1941). Whatley & Coles (1987) recorded it from Late Miocene to

Quaternary sediments in the central North Atlantic. Rosenfeld & Bein (1978)

recorded this species between 574 m and 2 859 m off north-western Africa.

Brady (1880) recovered Echinocythereis irpex from three sites in the central

and South Atlantic, at depths between 900 m and 2 850 m.

We have recorded E. whatleyi over a latitudinal range of 19°S—36°S

(Fig. 37) and a depth range of 730-2 916 m (Lower Neritic to Abyssal zones—

Fig. 38). Most of our records lie within the Upper Bathyal Zone but the species

308 ANNALS OF THE SOUTH AFRICAN MUSEUM

water depth,

NERITIC

ABYSSAL

LOWER

BATHYAL

latitude’S

30 35

Fig. 37. Latitude and water depth of samples bearing Echinocythereis whatleyi sp. nov.

UPPER

NERITIC | BATHYAL

Echinocythereis whatleyi

low at base of

salinity minimum

zone \

PS maximum at AAIW/NADW

boundary

LOWER

BATHYAL

water depth, km

ABYSSAL

Fig. 38. Echinocythereis whatleyi sp. nov. as percentage of total ostracod fauna plotted against

water depth. Values are three point running means.

DEEP-WATER QUATERNARY OSTRACODA 309

is most abundant at the boundary of the AAIW and NADW masses

(c. 1 500 m). There is an abundance low at the top of the Upper Bathyal Zone

(i.e. immediately below the Salinity Minimum Zone of the AAIW mass), and

the species decreases in abundance through the Lower Bathyal into the Abyssal

zones. Benson et al. (1983) recorded the species (as E. echinata) between

2 800 m and 3 000 m off Newfoundland.

Off Walvis Bay, Peypouquet & Benson (1980) noted Echinocythereis

between 974 m and 2 864 m, although they did not differentiate species. There

are too few data points to make a detailed comparison with Figure 38, but their

highest value does lie in the vicinity of 1500 _m. In contrast to our profile,

however, the Walvis Bay data indicate a sharp rise in abundance in the vicinity

of 3 km.

Genus Trachyleberis Brady, 1898

Trachyleberis sp. 3017

Fig. 42A-B

?‘Thalassocythere’ sp. B Cronin, 1983, pl. 4 (figs B, E, G).

Illustrated specimens

MF-0476, RV, TBD 6851, 2 916 m.

MF-0477, LV, TBD 6851, 2 916 m.

Remarks

The type species of Trachyleberis Brady, 1898, is Cythere scabrocuneata

Brady, 1880, and the holotype is lost. Puri & Hulings (1976, pl. 26 (figs 6, 8))

illustrated a topotype from the Inland Sea of Japan. Our species has less robust

spines, no AM and PM rims, and lacks the antero-dorsal ocular ridge, and is not

conspecific. In general aspect, however, it conforms with the genus.

Benson (e.g. Benson 1977, in Benson & Peypouquet 1983) seems to use the

nomen nudum ‘Thalassocythere’ for deep-water Trachyleberis-like species and,

judging from Benson (1977), when he lists (but does not illustrate) ‘Thalasso-

cythere’ acanthoderma from the Miocene at DSDP sites 356 and 357, it is

implied that Cythere acanthoderma Brady, 1880, is the comparative species for

this group. An illustration of ‘Thalassocythere’ acanthoderma (Brady, 1880)

from 3 000 m off Newfoundland (Benson et al. 1983, pl. 2 (fig. 9)), bears a close

resemblance to Brady’s (1880, pl. 18 (figs S5a—e)) original illustrations, but

differs from the lectotype of Cythere acanthoderma figured by Puri & Hulings

(1976), which is probably a juvenile, in possessing a pointed PM outline; the

lectotype has a rounded outline. Coles & Whatley (1989) have formalized the

taxonomy of this group by erecting the genus Legitimocythere, with the type

species Cythere acanthoderma Brady, 1880. Our species differs from L. acantho-

derma (Brady, 1880) (as in Brady’s original illustrations) in lacking an AM rim,

310 ANNALS OF THE SOUTH AFRICAN MUSEUM

in having a concave VM outline in lateral view, and having fewer and less

massive and ‘ragged’ spines. It may be conspecific with ?‘Thalassocythere’ sp. B

(Cronin, 1983), although our species has a less dense pattern of spines. R. C.

Whatley (pers. comm. 1988) has suggested that our specimens are probably

juveniles of Legitimocythere acanthoderma (Brady, 1880).

Rosenfeld & Bein (1978) did not record any trachyleberid-like species from

off north-western Africa.

In the south-eastern Atlantic, Trachyleberis sp. 3017 is confined to the

Abyssal Zone, where we have recorded it from two sites at 2 916 m and 4 736 m

water depth. Here it consitutes 1 per cent and 33 per cent of the total ostracod

fauna, respectively. Table 5 summarizes the geographical and depth ranges of

the documented deep-sea species of Trachyleberis.

TABLE 5

Distribution of deep-sea species of the genus Trachyleberis (including the nomen nudum

‘Thalassocythere”™).

Species Reference Age Location Baty

Trachyleberis Brady (1880) Quaternary Atlantic, Indian, 1 600-5 500

acanthoderma Pacific

Benson et al. (1983) Quaternary Newfoundland 2 600-3 210

Ducasse & Pey- Miocene— NE Atlantic (DSDP ?

pouquet (1979) Quaternary 403, 405)

Whatley & Coles Miocene- N Atlantic(DSDP 2 445-3 884

(1987) Quaternary 606-611)

Trachyleberis sp.3017 this paper Quaternary SE Atlantic 2 916-4 736

Trachyleberis sp. B Cronin (1983) Quaternary SE USA 341-739

* ‘Thalassocythere’ = Legitimocythere Coles & Whatley, 1989.

Genus Henryhowella Puri, 1957

Henryhowella has been widely reported in the literature from modern and

Cenozoic deep-water sediments. The type species for Henryhowella is Cythere

evax Ulrich & Bassler, 1904, and Puri’s original diagnosis (1957 new name =

Howella Puri, 1956), together with the type description of Cythereis garretti

Howe & Mcguirt, 1935 (in Howe & graduate students 1935) (which is the type

species for Echinocythereis Puri, 1954), distinguishes the genus Henryhowella

from its close relative Echinocythereis on two criteria: 1. the possession of ‘three

well-developed longitudinal rows of spines in the posterior half of the carapace’;

2. having a single, hooked anterior MS (Echinocythereis has two small rounded

anterior MS).

DEEP-WATER QUATERNARY OSTRACODA ot

Conventional wisdom is to ascribe certain spinose taxa with a single hooked

anterior MS to Henryhowella, irrespective of whether they possess a triplicate

posterior ornamentation (e.g. Uffenorde 1981; Whatley & Coles 1987; Steineck

et al. 1988). Those that do possess the latter feature are invariably placed in

Henryhowella asperrima (Reuss, 1850) (e.g. Van den Bold 1960; Cronin 1983;

Whatley & Coles 1987). This has the effect of modifying the generic concept and

blurring its definition to the point of causing confusion with genera such as

Rocaleberis Bertels, 1969. It also reduces the only substantive distinguishing

feature between Echinocythereis and Henryhowella to their different MS

patterns. As a consequence, Cythere evax Ulrich & Bassler, 1904, should be

considered a synonym of Cypridina asperrima Reuss, 1850 (e.g. Van den Bold

1957b, 1960), which becomes the type species of the genus Henryhowella. A

problem here is that in his type description, Reuss (1850: 74), specifically stated

that Cypridina asperrima has two posterior ridges and a median longitudinal

furrow in the posterior part of the valve. Keij (1957) and Van den Bold (1960)

have examined topotypes for Reuss’s original material and both assumed that

Reuss misidentified the valve architecture, although there has been no modern

re-illustration of his topotypic material, nor the erection of a lectotype, if indeed

the holotype is lost.

Henryhowella melobesioides (Brady, 1869)

Figs 42C-F, 43A-F, 44A-D, 47A

Cythere melobesioides Brady, 1869: 162, pl. 12 (figs 10-11); 1880: 108, pl. 18 (figs le-g). Puri

& Hulings, 1976, pl. 25 (figs 1-2).

Cythere nodulifera Brady, 1869: 163, pl. 19 (figs 24-25).

Henryhowella sp. Keeler, 1981: 162-163, pl. 9 (fig. 14).

Henryhowella sp. Boomer, 1985: 25-27, pl. 1 (figs 6-8, 18).

non Henryhowella sp. Boomer, 1985: 25-27, pl. 3 (figs 38-39).

non Cythere melobesioides Brady, 1869. Brady, 1880, pl. 18 (figs 1a—d).

Illustrated specimens

MF-0478, RV, TBD 311, 184 m.

MF-0479, LV, TBD 311, 184 m.

MF-0480, LV, TBD 3561, 655 m.

MF-0481, RV, TBD 3561, 655 m.

MF-0482, LV, TBD 3704, 941 m

MF-0483, RV, TBD 3704, 941 m.

MF-0484, RV, TBD 3383, 990 m.

MF-0485, RV, TBD 3383, 990 m.

MF-0486, LV, TBD 3383, 990 m.

MF-0487, LV, TBD 6851, 2 916 m.

MF-0488, LV, TBD 6851, 2 916 m.

MF-0489, LV, TBD 3383, 990 m.

312 ANNALS OF THE SOUTH AFRICAN MUSEUM

Remarks

Accepting the current interpretation of non-plicate morphology, this species

can be accommodated in the genus Henryhowella, and there are four species to

which our material can be compared: Henryhowella asperrima (Reuss, 1850),

Henryhowella dasyderma (Brady, 1880), Henryhowella digitalis Levinson, 1974

(in LeRoy & Levinson 1974), and Henryhowella melobesioides (Brady, 1869).

As discussed above, tri-plicate species (i.e. the ‘typical’ Henryhowella mor-

phology) are generally automatically assumed to belong within H. asperrima

(Reuss). This has led to the grouping of taxa whose synonomy appears doubtful

but for which resolution requires redefinition of the types. To gauge the problem

compare the following: Keij (1957, pl. 12 (figs 1-2)); Van den Bold (1960, pl. 4

(fig. 10)); Colalongo (1965, pl. 11 (figs 3-8)); LeRoy & Levinson (1974, pl. 12

(fig. 1)); Rosenfeld & Bein (1978, pl. 1 (fig. 23)); Cronin (1983, pl. 4 (fig. F));

Whatley & Coles (1987, pl. 5 (figs 9-11)). None of our material fits comfortably

into the taxon currently interpreted as Henryhowella asperrima, even allowing

for the range of morphological variation accepted by other authors. All the

specimens that we have recovered have very weak or no lineation of spines in

the posterior part of the valves; there are never three well-defined rows or

ridges. The closest approximation to a tri-plicate morphology is shown in

Figure 43C, but such are isolated examples in populations where there is grada-

tion to the completely non-plicate state. As observed by Steinick et al. (1988) for

their deep-sea Pacific populations, we feel unable to place specimens into a poss-

ibly polytaxonomic category.

Tertiary species referred to H. asperrima have been recorded from the

vicinity of south-western Africa by Van den Bold (1966—Lower Miocene of

Gabon) and Frewin (1987—Middle—Upper Eocene of the Agulhas Bank).

Dingle (1976) recorded a form very close to Frewin’s species as Henryhowella

sp. This ranges from Lower Eocene to Upper Oligocene in the J(c)—1 borehole

on the continental shelf off Natal (south-eastern Africa), and is probably the

same species as a worn specimen referred to Indet. sp. 2314 from Upper Ceno-

manian strata in the same borehole (Dingle 1985). The latter record was

possibly a downhole contaminant from overlying Tertiary strata. These local

records are all probably of the same species (whether or not they can ultimately

be referred to Reuss’s species is an open question), which seems to have a range

Lower Eocene to Miocene.

Henryhowella digitalis Levinson, 1974 (in LeRoy & Levinson 1974), was

erected as a variety of H. asperrima to accommodate specimens with a reticu-

late/spinose ornamentation. LeRoy & Levinson (1974) speculated that this was a

‘deep-water variant’ of H. asperrima. Some of our specimens do show a degree

of reticulation, but it is not a consistently developed feature.

Henryhowella dasyderma (Brady, 1880) is a non-plicate species. Brady

(1880) included several morphotypes in his original description, one of which

(1880, pl. 17 (fig. 4e-f)) has a sharp ventro-lateral ridge. The lectotype desig-

nated by Puri & Hulings (1976, pl. 11 (figs 10—11)) from ‘Challenger’ site 296

DEEP-WATER QUATERNARY OSTRACODA 313

(south-eastern Pacific) is very similar to our material, but we have not assigned

our specimens to it, because Brady himself (1880) believed that the populations

that he recovered from off the south-western Cape were closer to Cythere

melobesioides Brady, 1869. However, he did remark (1880: 105) that Cythere

dasyderma was a deep-water taxon that occurs world-wide. It has been

subsequently recorded by Rosenfeld & Bein (1978) from 1 029-2 480 m off

north-western Africa, and Whatley & Coles (1987) from early Pliocene to

Quaternary of the North Atlantic.

Henryhowella melobesioides (Brady, 1869) was recorded by Brady (1880)

from ‘Challenger’ site 142 off the Cape Peninsula in 150 fm (274m) water

depth. The type species was from Mauritius and Brady (1880) also identified it

from Australia, but these (pl. 18 (fig. la—d)) appear not to be conspecific. Our

material is conspecific with the specimen illustrated by Puri & Hulings (1976,

pl. 25 (figs 1-2)), but there is some variation in ornamentation within the popu-

lation, particularly in the prominence of a weak ridge that lies almost parallel to

the postero-ventral margin, a feature noted in the illustration in Brady (1880,

pl. 18 (fig. 1g)). The lateral surface spines are arranged concentrically in the

anterior part of the valve, and randomly or with a weak elongation that tends to

converge into a chevron with its apex towards the PM. No consistent morpholo-

gical variations are observed between specimens from different depths, although

individuals from shallower water tend to have the more nodose spines described

by Brady (1880). MS patterns are identical when observed over a range 655-

2 916 m (no good views were obtained from shallow-water examples). It is poss-

ible that we have more than one species in our populations but, until the uncer-

tainty of the taxonomic position of forms currently referred to H. asperrima

(Reuss) and their relationship to H. dasyderma (Brady) have been clarified,

there seems little point in attempting to subdivide the various morphotypes of

our H. melobesioides (Brady) population.

Off south-western Africa, Henryhowella melobesioides (Brady, 1869) has

been found over a latitudinal range 19°S~36°S (Fig. 39), and a depth range of

100-2 916 m (Fig. 40). In the Neritic Zone, it is confined to water greater than

600 m north of 29°S, where we suspect it cannot survive in either low oxygen-

ated water (associated with the upwelling cells north of 25°S) or influxes of less

saline and/or suspensate-rich water from the Orange River on the continental

shelf between 25°S and 29°S. The upwelling cells on the shelf south of 29°S do

not sustain sufficiently high productivity in the water column to result in low

oxygen layers.

Figure 40 shows that on the continental shelf (i.e. less than 300 m),

FH. melobesioides is a minor element in the ostracod population (generally

<10%). Its abundance steadily increases with water depth, so that overall within

the Neritic Zone it constitutes a mean of 31 per cent (range 0,1-100%). In the

Upper Bathyal Zone it is the dominant ostracod taxon, generally forming more

than 60 per cent of the total population (mean of 73%, range 19-100%)

but, between about 800m and 1 000m, which includes the Neritic/Bathyal

314 ANNALS OF THE SOUTH AFRICAN MUSEUM

" oO

—-— = modern specimens ABYSSAL

ere Ae ih es eat gente olin) realm eenay ere ny oy a (an ee

x = LOWER BATHYAL

fe oO

ret =a oa. ae iw oO pe eee a ee See

ce) 0 ee a) a) oO

bs oes 5 / oO

2 of of ay o UPPER BATHYAL

= | ww ees

oO = oO --* "

1 o wane, pass | a Eg areae NA — Se oO a aa o-—#X\ — — =

DO - ao ie “oO \

Z oO oO Ff B \

oO ea Oo \\

| O \

NERITIC C8 Ja: eo ce

RS: Go.

L OW Ou APE) WN _9 ao So penn ay

: eae

20 25 30 35

latitude °S

Fig. 39. Latitude and water depth of samples bearing Henryhowella melobesioides (Brady,

1869). Note the absence of this species from the low O2, and low salinity/high suspensate conti-

melobesioides

Henr yhowella

Fig. 40. Henryhowella melobesioides (Brady, 1869) .as percentage of total ostracod fauna

100 =

nental shelves off Walvis Bay/Liideritz, and Orange River, respectively.

| |

NERITIC ! BATHYAL | ABYSSAL

| UPPER | LOWER |

decrease in | i |

abundance ay | fo 7 |

at fh |

We | Vi |

= h i decrease in

co / |) oh ane | abundance at

yy es AAIW/ NADW

ip boundary

i" |

| | | 1 :

re t = =

| | Aa |

ir ui |

it |

| | |

Lind

A Wise | | @ |

al om | | | |

he | | |

Ua rh | | |

1 Gee low abundance | |

ae mn < on shelf | | |

O 1 2,

water depth, km

plotted against water depth. Values are three point running means.

DEEP-WATER QUATERNARY OSTRACODA 315

boundary, there are large fluctuations in its abundance. Similarly, on

approaching the Upper/Lower Bathyal Zone boundary (i.e. the shear zone

between the AAIW and NADW masses), there is a large fall in abundance, that

continues through the Lower Bathyal Zone (mean 39%, range 28-71%) into the

Abyssal Zone (mean 20%, range 6-34%). Clearly, this species has a wide toler-

ance of temperature and salinity, but it is relatively less successful in unstable, or

mixed zones. In this respect it shows a distribution pattern that is the reverse of

Buntonia rosenfeldi sp. nov.

Modern specimens were identified on two criteria: shell transparency and

good preservation of spines. They were encountered in two distinct areas. North

of 26°S the entire distribution zone contains modern valves (i.e. in both the

Lower Neritic and Upper Bathyal Zones), whereas farther south the modern

population is confined between 29°S and 35°S and almost solely to the Neritic

Zone (Fig. 39).

Peypouquet & Benson (1980) recorded Henryhowella from their traverse

off Walvis Bay. There are too few data points to make a meaningful comparison

with our results, but a plot of the abundance of Henryhowella (Fig. 41) indicates

similar trends to Figure 40. We do not Know if the species they recorded was

H. melobesioides but suspect so, because the latitudinal ranges of the data sets

overlap.

NERITIC BATHYAL ABYSSAL

UPPER LOWER

(2)

Henryhowella spp.

water depth, km

Fig. 41. Henryhowella species as percentage of total ostracod fauna plotted against water depth

for a profile off Walvis Bay. Data computed from Peypouquet & Benson (1980).

316 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 42. A-B. Trachyleberis sp. 3017, TBD 6851, 2 916m. A. SAM—PO-MF-0476, RV,

SEM 3017. B. SAM-PQ-MF-0477, LV, SEM 3024. C-F. Henryhowella melobesioides

(Brady, 1869). C. SAM—PQ-MF-0478, RV, TBD 311, 184m, SEM 2625. D. SAM—-PQ-

MF—0479, LV, TBD 311, 184 m, SEM 2626. E. SAM—PQ-MF-0480, LV, TBD 3561, 655 m,

SEM 2591. F. SAM-PQ-MF-0481, RV internal view, TBD 3561, 655 m, SEM 2594.

Scale bars = 100 microns.

DEEP-WATER QUATERNARY OSTRACODA Bik

Fig. 43. A-F. Henryhowella melobesioides (Brady, 1869). A. SAM—-PQ-MF-0482, LV,

TBD 3704, 941 m, SEM 2630. B. SAM—PQ-MEF-0483, RV internal view, TBD 3704, 941 m,

SEM 2632. C. SAM-PQ-MF-0484, RV, TBD 3383, 990m, SEM 2552. D. SAM-—

PQ-MF-—0485, RV internal view, TBD 3383, 990 m, SEM 2561. E. SAM-POQ-MEF-0486,

LV, TBD 3383, 990m, SEM 2551. F. SAM-—POQ-MF-0487, LV, TBD 6851, 2 916 m,

SEM 2636. Scale bars = 100 microns.

318 ANNALS OF THE SOUTH AFRICAN MUSEUM

—- Ho om

ra) O

VE Ja

eee ae fe)

C D o

Fig. 44. MS of Henryhowella melobesioides (Brady, 1869). A. SAM—PQ-MF-0481, RV,

TBD 3851, 655 m, SEM 2621. B. SAM—PQ-MF-0483, RV, TBD 3704, 941 m, SEM 2634.

C. SAM-PQ-MF-0489, LV, TBD 3383, 990 m, SEM 2556. D. SAM—-PQ-MF-0488, LV,

TBD 6851, 2 916 m, SEM 2639. Open dots are normal pores. Scale bars are 100 microns.

Subfamily Pennyellinae Neale, 1975

Neale (1975) established this taxonomic category to accommodate certain

blind, reticulate trachyleberids, and identified three genera that belonged

here: Pennyella Neale, 1974, Santonian (Western Australia—Neale 1974) to

Maastrichtian (north-western Pacific—Swain 1973); Agulhasina Dingle, 1971,

Maastrichtian (southern Africa); Agrenocythere Benson, 1972, Eocene (Atlan-

tic) to Recent (pandemic). We now add a fourth: Rugocythereis gen. nov.,

Miocene to Quaternary (pandemic—Brady 1880; Whatley & Coles 1987).

Rugocythereis gen. nov.

Derivation of name

Latin rugosa—rough, reference to coarse texture of surface ornamentation.

Type species

‘Oxycythereis’ horridus Whatley & Coles, 1987.

Diagnosis

Blind, elongate-sub-quadrate trachyleberid with coarsely reticulate and/or

stout spinose ornamentation. Strongly sexually dimorphic with males signifi-

cantly more elongate than females. Females typically possess an antero-dorsal

marginal frill. Valves are inflated postero-ventrally and compressed in the AM

DEEP-WATER QUATERNARY OSTRACODA 319

areas, with strong AM and PM rims. Typically there is a prominent cleft

between the PM rim and the area of postero-ventral inflation. Hinge is modified

amphidont, with weak ATE in RV.

Remarks

Rugocythereis gen. nov. is a pandemic genus that includes several taxa pre-

viously placed in the nomen nudum ‘Oxycythereis’ Benson, 1974. It is closest to

Pennyella Neale, 1974, but the two genera differ on the following features:

1. Rugocythereis lacks the prominent vertical postero-dorsal ridge.

2. Rugocythereis lacks the prominent ventro-lateral ridge that terminates in a

posterior elevation.

3. Pennyella has a more triangular-shaped PM outline, with a distinctive

postero-dorsal concavity.

4. Females of Rugocythereis have a distinctive antero-dorsal marginal frill.

5. The hinges are somewhat different: Pennyella has a peg-like ATE in the RV,

with a post-adjacent rounded socket, whereas in Rugocythereis the RV ATE is

low and elongate, has a narrow grove on its dorsal side, and has no post-

adjacent rounded socket.

The two genera have very similar MS patterns, which include a ventrally

deflected second adductor and two very close, almost fused, third and fourth

adductors.

Rugocythereis gen. nov. is a deep-water genus, for which four species have

been formally described: R. horridus (Whatley & Coles, 1987), R. dorsoserrata

(Brady, 1880, emend. Puri & Hulings, 1976), and two species originally placed

in Pennyella (P. fortedimorphica Coles & Whatley, 1989, and P. praedorsoser-

rata Coles and Whatley, 1989). In addition, Whatley & Coles (1987) recorded

two possible species in open nomenclature (‘Oxycythereis’ sp. 1 and ‘“Oxycy-

thereis’ sp. 2). Several other modern and fossil species of Rugocythereis may

be included in the nomen nudum ‘Oxycythereis’ (see Kempf 1986a, 1986b),

but their status is uncertain. This is because the references have lacked either

illustrations or descriptions or both, which introduces confusion over

the comparability of R. dorsoserrata (Brady, 1880) and the validity of

additional specific taxa (e.g. Benson 1977; Peypouquet & Benson 1980;

Benson et al. 1983).

Table 6 lists known and possible taxa that belong in Rugocythereis gen. nov.

Given the limitations of the uncertain taxa, the genus may have an age range of

Eocene to Recent and a water depth range for modern species of 730-3 526 m.

Guernet (1985, pl. 4 (fig. 9)) described a species under Wichmanella?

cf. W.? reticulata, which has a similar valve outline and ornamentation to

R. horridus. This taxon was recorded in Lower Eocene strata at DSDP site 245

in the south-western Indian Ocean.

No species referable to Rugocythereis (including the nomen nudum taxa

‘Oxycythereis’) was reported from Quaternary deep-water sites off the south-

eastern USA (Cronin 1983) or north-western Africa (Rosenfeld & Bein 1978).

320

ANNALS OF THE SOUTH AFRICAN MUSEUM

TABLE 6

Geographical and water depth distribution of species of Rugocythereis gen. nov.

Quaternary

Species Reference Age Location depth

(m)

Rugocythereis dorso- Brady (1880) Quaternary S Atlantic 2 850

serrata (Brady, 1880)

Rugocythereis horridus Whatley & Coles Miocene- N Atlantic 2 445-3 526

(1987) Quaternary

Pliocene— SW Pacific

Quaternary

Miocene SW Indian

Ducasse & Pey- Quaternary NE Atlantic 3 000

pouquet (1979) (DSDP 405)

this paper Quaternary SE Atlantic 750—7 NG

Rugocythereis? spp. Benson (1974) Eocene— W Indian (DSDP v

Pliocene D338)

Benson et al. Quaternary NW Atlantic 3 210

(1983)

Benson (1977) Eocene— S Atlantic (DSDP u

Pleistocene 350, 357)

Peypouquet & Quaternary SE Atlantic 2 094—2 644

Benson (1980)

Rugocythereis sp. 1 Whatley & Coles | Miocene N Atlantic

(1987)

Rugocythereis sp. 2 Whatley & Coles _—_ Pliocene N Atlantic

(1987)

Rugocythereis horridus (Whatley & Coles, 1987)

Figs 47B-F, 48

‘Oxycythereis’ horridus Whatley & Coles, 1987: 76-78, pl. 5 (figs 18-22).

Henryhowella sp. Boomer, 1985: 25-27, pl. 3 (figs 38-39).

non Henryhowella sp. Boomer, 1985: 25-27, pl. 1 (figs 6-8).

Illustrated specimens

MF-0490, RV, TBD 2677, 1 662 m.

MF-0491, LV, TBD 6851, 2 916 m.

MF-—0492, RV, TBD 6851, 2 916 m.

MF-—0493, RV, TBD 6851, 2 916 m.

Remarks

Rugocythereis horridus (Whatley & Coles) was originally described from

Miocene to Quaternary strata at DSDP sites from Leg 94 in the north central

Atlantic, and was also recorded from Pliocene to Quaternary in the south-

DEEP-WATER QUATERNARY OSTRACODA By)

western Pacific, and Miocene from the Indian Ocean (Whatley & Coles 1987).

We record it in the south-eastern Atlantic between 29°S and 36°S, in water

depths of 730-2 916 m (Fig. 45). The species was found in only 16 per cent of

the bathyal and abyssal sites, and Figure 46 shows that R. horridus ranges from

lower neritic to abyssal depths and that it is most abundant in the Upper Bathyal

Zone. In the lower part of the Neritic Zone, abundances are low (mean: 4%

total ostracod fauna, range nil), but in the Bathyal Zone the species is relatively

abundant (mean: 24%, range 4-100%). There appears to be a decrease in abun-

dance with increasing depth through the Bathyal Zone, and the single site in the

Abyssal Zone (2 916 m) has the lowest abundance of our data set (2%).

The species recorded by Ducasse & Peypouquet (1979) as ‘Oxycythereis’

dorsoserata [sic] from DSDP site 405 in the Rockall Basin (north-eastern Atlan-

tic) probably belongs in R. horridus.

Rugocythereis horridus is closely related to R. dorsoserrata (Brady, 1880),

which has been re-illustrated by Puri & Hulings (1976), who selected a lectotype

from Brady’s original ‘Challenger’ material. Positive identifications of Rugo-

cythereis dorsoserrata (Brady, 1880) have been: Brady’s original record from

2 605 m (1 425 fm) north of Tristan da Cunha in the South Atlantic; Whatley &

Coles’s (1987) record from Miocene—Quaternary strata from DSDP Leg 94 sites

in the North Atlantic; and two specimens identified as Cythere suhmi Brady,

1880, by Ducasse & Peypouquet (1979, pl. 2 (figs 5—6)) from the late Pliocene

@ = modern specimens

ABYSSAL

LOWER

BATHYAL

water depth, km

BATHYAL

NERITIC

30 35

latitude °S

Fig. 45. Latitude and water depth of samples bearing Rugocythereis horridus (Whatley & Coles,

1987).

322 ANNALS OF THE SOUTH AFRICAN MUSEUM

100 %

NERITIC ABYSSAL

% Rugocythereis rogersi

1 2 3

water depth, km

Fig. 46. Rugocythereis horridus (Whatley & Coles, 1987) as percentage of total ostracod fauna

plotted against water depth. Values have not been smoothed.

of DSDP site 403 on Hatton Bank (north-eastern Atlantic), which are probably

conspecific. These records suggest an age range Miocene to Quaternary for

R. dorsoserrata.

Benson et al. (1983) recorded ‘Oxycythereis’ dorsoserrata (Brady, 1880)

(which they equated with ‘O.’ dorsoserrata of Ducasse & Peypouqueti 1979)

from a sample at 3 210 m off Newfoundland, but did not illustrate the specimen.

Peypouquet & Benson (1980) recorded ‘Oxycythereis’ from their traverses

in the Cape and Angola basins. These may refer to species of Rugocythereis,

although there were no accompanying illustrations. The data are too sparse to

plot, but abundances at the three sites were: Walvis transect—2 094 m, 0,2 per

cent; 2 117m, 1 per cent; Angola Basin—2 644 m, 0,7 per cent. These are

lower values than we have determined for similar depths, but indicate that the

taxon is rare.

Subfamily Bradleyinae Benson, 1972

Genus Poseidonamicus Benson, 1972

Whatley et al. (1983) have expressed reservations about the suprageneric

placement of Poseidonamicus, but we will follow Benson’s original classification

for the present.

DEEP-WATER QUATERNARY OSTRACODA 323

: ow

: *

Fig. 47. A. Henryhowella melobesioides (Brady, 1869), SAM—PQ-MF-0488, LV internal view,

TBD 6851, 2 916m, SEM 2638. B-F. Rugocythereis horridus (Whatley & Coles, 1987).

B. SAM-PQ-MF-0490, RV, TBD 2677, 1662 m, SEM 3030. C-F. TBD 6851, 2 916 m.

C. SAM-PQ-MF-0491, LV, SEM 3008. D. SAM-—PQ-MF-0492, RV, SEM 3009. E. SAM-

PQ-—MF-0493, RV internal view, SEM 3012. F. SAM—PQ-MF-0493, RV ATE and PTE,

SEM 3013 and 3014. Scale bars = 100 microns.

324 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 48. MS of Rugocythereis horridus (Whatley & Coles,:1987). SAM—PQ-—MF-0493, RV,

TBD 6851, 2 916 m, SEM 3015. Open dots are normal pores. Scale bar = 100 microns.

NERITIC BATHYAL ABYSSAL

be)

je)

P. major

Poseidonamicus spp.

—

water depth, km

Fig. 49. Latitude and water depth of samples bearing Poseidonamicus species. The populations

of P. major Benson, 1972 (deep-water species), and P. panopsus Whatley & Dingle, 1989

(shallow-water species) are outlined. They are separated by 1500 m of the water column,

which contains several effective physico-chemical barriers.

DEEP-WATER QUATERNARY OSTRACODA 325

Whatley (1985) discussed the colonization of bathyal and abyssal environ-

ments by species of Poseidonamicus, and he concluded that since early

Palaeogene time the genus has been confined to water depths greater than

1 000 m. However, recent work on the ostracod fauna offshore south-western

Africa has located two species of the genus, one of which is blind and lives at

abyssal depths (P. major Benson, 1972), and one of which is sighted and lives on

the outer continental shelf/upper slope (P. panopsus Whatley & Dingle, 1989).

Figure 49 shows the distribution and abundances of these two species in the

south-eastern Cape Basin. It is significant that the habitats of the two species,

which are both extant, are separated by 1500 m of water that includes the

Salinity Minimum Zone of the AAIW and the boundary between the AAIW

and NADW water masses. These must be very effective barriers in maintaining

the identity of the two species.

Poseidonamicus major Benson, 1972

Figs 50A—F, 51A-B

Poseidonamicus major Benson, 1972: 52-53, pl. 8 (fig. 5), pl. 10 (figs 1-6), text-figs 20, 22.

Illustrated specimens

MF-0494, RV, TBD 6851, 2 916 m.

MF-0495, LV, TBD 6851, 2 916 m.

MF-0496, LV, TBD 6851, 2 916 m.

MF-0497, RV, TBD 6851, 2 916 m.

Remarks

Our material is identical to the holotype (USNM 174335), except for its

MS pattern, which in the Cape Basin specimens show an indented ventral scar in

the anterior pair, and two ‘dog’s bone’-shaped central scars in the adductors.

Poseidonamicus major differs from the shelf/upper slope species of the

genus that has recently been discovered living in neritic depths (120-545 m) off

south-western Africa (P. panopsus Whatley & Dingle, 1989) in several respects.

The new species has a prominent eye tubercle, is generally more quadrate in

lateral outline, and lacks the strong, curved anterior dorso-lateral ridge that is a

characteristic feature of P. major. Their MS are very similar, although in

P. panopsus the lower anterior scar is more V-shaped than in our specimens of

P. major.

Frewin (1987) recorded an Eocene species from the Agulhas Bank as

?Poseidonamicus sp. A126. This is a sighted form that has some architectural

features similar to the type species of Poseidonamicus, but whose overall

morphology suggests that it belongs to an undescribed taxon.

The holotype of Poseidonamicus major is from the Mozambique Channel

(south-west of Europa Island) at a depth of 2 995 m, where Benson (1972)

recorded a bottom water temperature of 1,6°C. Off south-western Africa, we

326 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 50. A-F. Poseidonamicus major Benson, 1972, TBD 6851, 2916m. A. SAM-—PQ-

MF-0494, RV, SEM 2929. B. SAM—POQ-MF-0495, LV, SEM 2926. C. SAM-—PO-MF-0496,

LV internal view, SEM 2931. D. SAM-—PC-—MF-0497, RV internal view, SEM 2933.

E. SAM-—PQ-MF-0496, LV MS, SEM 2932. F. SAM—PQ-MF-0497, RV MS, SEM 2935.

Scale bars = 100 microns.

DEEP-WATER QUATERNARY OSTRACODA B77)

A B

Fig. 51. MS of Poseidonamicus major Benson, 1972. A. SAM—PQ-MF-0497, RV, TBD 6851,

2 916 m, SEM 2935. B. USNM 174354, RV, IIOE 363B, 2 995 m, Mozambique Channel (from

Benson 1972, fig. 22B). Scale bars = 100 microns.

BAK

Fig. 52. A-B, D. Indet. sp. 62, TBD 3870, 1 026m. A. SAM-PQ-MF-0498, LV. B, D.

SAM-PO-MF-0499, RV. B. Internal view. D. MS. C. Indet. sp. 23, SAM-—PQ-—MF-0500,

TBD 3174, 1 050 m. Scale bars: A—C = 100 microns; D = 30 microns.

328 ANNALS OF THE SOUTH AFRICAN MUSEUM

found the species at two sites within the Abyssal Zone: TBD 3355 (2 070 m) and

TBD 6851 (2 916 m) (Fig. 49). In the former, which lies at the top of the

Abyssal Zone, P. major accounts for 14 per cent of the total ostracod fauna and

is the third most abundant taxon, but all the specimens were relict. At

TBD 6851 (2 916 m), this species is the second most abundant taxon (29%),

6 per cent of which were modern specimens (1,7% of total ostracods).

In his original discussion of Poseidonamicus, Benson (1972) erected four

new species, all of which are extant: P. major, P. minor, P. nudus, and

P. pintoi. He did not quote depth ranges for individual species, but reference to

his table 2 shows the ranges that he recorded for the modern genus in various

oceans, as follows: Atlantic 1 227—5 020 m; Indian 1 190-3 995 m; and Pacific

2 089-3 292 m. Whatley (1985) has discussed the evolutionary history of the

genus and concluded that it originated in the south-western Pacific, probably

in the Palaeocene, from a species such as Hermanites sagitta Bate, 1972, which

had a continental-shelf habitat. During a phase of rapid mutation in the early

Tertiary, the earliest forms of Poseidonamicus migrated into bathyal and later

(in the Miocene) into abyssal habitats. Whatley (1985) did not have sufficient data

to postulate the evolution of P. major, which is morphologically distinct from

the other Tertiary forms. He recorded it in the Miocene of the south-western

Pacific, but Benson (1972: 53) stated that it occurs in the Oligocene of DSDP

site 117 (north-eastern Atlantic). Benson & Peypouquet (1983) recorded several

species of the genus from Neogene horizons at DSDP sites in the western South

Atlantic (sites 516, 517, and 518), including two new species (P. miocenicus and

P. riograndensis), but did not mention P. major specifically. Whatley & Coles

(1987) recorded Poseidonamicus sp. cf. P. major and Poseidonamicus sp. cf.

P. pintoi as ranging late Miocene to Quaternary at DSDP Leg 94 sites in the

North Atlantic.

As far as we can gauge from the literature, P. major has the following age

ranges: south-western Pacific—Miocene to Recent (bathyal—abyssal); south-

western Atlantic—Miocene to ?Recent; north-eastern Atlantic— Oligocene;

south-western Indian—Recent (abyssal); and, south-eastern Atlantic— Quater-

nary (abyssal); and North Atlantic, as Poseidonamicus cf. P. major—late

Miocene to Quaternary.

Indeterminate taxa

Indet. sp. 62

Fig. 52A-B, D

Two living valves were recovered from sample TBD 3870 at a water depth

of 1 026 m. This ovate species has a short, straight DM and prominent anterior

and posterior cardinal angles. It has a merodont hinge and a MS pattern consist-

ing of a small rounded anterior scar and three elongate adductors above a

smaller oval fourth adductor. It may be related to Krithe (R. C. Whatley, pers.

comm. 1988).

DEEP-WATER QUATERNARY OSTRACODA 329

Indet sp. 23

Fig. 52€

Two fragments of the anterior ends of RV were recovered from sample

TBD 3174 at a water depth of 1 050 m. The species has a broadly rounded AM

with a narrow, spinose rim. There is a prominent spinose ridge in the antero-

ventral region, but otherwise the anterior part of the valve surface is smooth. It

may belong in Bathycythere (R. C. Whatley, pers. comm. 1988).

DISCUSSION

A total of 1 023 autochthonous specimens were recovered from 45 sediment

samples in water depths greater than 900 m off south-western Africa (only one

sample of the original 46 in our data set was barren of ostracods). These

represent 31 species, of which four are neritic taxa whose ranges extend 100 m

or less into depths that we equate with the Bathyal Zone. The 27 genuinely

deep-water species are assigned to 16 genera and two indeterminate categories.

DEPTH RANGES AND FAUNAL ZONES

Figure 53 shows the depth ranges of all the species we have isolated, and

the inset plots the turnover rate (appearances/disappearances) against depth

(summed for 100 m intervals). These data indicate that important changes in

composition of the ostracod faunas occur within three depth zones:

900-1 100 m; 1 300-1 700 m; and 2 000-2 100 m. (The fourth peak on the

right-hand-side of the inset is an artefact caused by the small number of samples

available in water deeper than 2 100m.) Figures 54-56 and Table 7 show

further details of these faunal changes and allow us to isolate with more

precision the depths at which they occur.

Between 900 m and 1 050 m, ten species appear or disappear, with a further

seven species passing through the zone unaffected (Fig. 54). Four of the species

that die out are taxa that also occur in relatively shallow water, and have no sig-

nificant presence in the deep-water faunas; we consider these to be stragglers

from the neritic assemblages, and they have not been treated in the taxonomic

section of this paper (Buntonia sp. 34, Xestoleberis sp. nov., Bythocypris sp. 42,

and ?Bradleya sp. 56). Considering species that occur in more than one sample

(i.e. those for which we can determine a depth range), 57 per cent of the turnover

events take place between 950 m and 1 000 m, 29 per cent between 900 m and

950 m, and 14 per cent between 1 000 m and 1 050 m. The appearance and

disappearance, respectively, of Parakrithe sp. 10 and ?Bradleya sp. 56 at 945 m

suggests that the significant faunal change occurs closer to 950 m than to 1 000 m.

It is unlikely, in fact, to occur at a specific depth for individual or all species, but

for the purposes of discussion and diagrammatic presentation, we nominally take

950 m as the depth at which the boundary between the neritic and bathyal ostra-

cod assemblages lies. The reality of a major faunal break at approximately this

330 ANNALS OF THE SOUTH AFRICAN MUSEUM

Trachyleberis sp. 3017 ABYSSAL

| |

Krithe peypouqueti | |

Krithe rex | | s

Cytherella sp. 3027 : eit | e

Krithe sp. 22 | BATHYAL | mt

Dutoitella suhmi | a

AN SEES / MEE custeuls NERITIC : UPPER : : a 20 7

Poseidonamicus major BATHYAL g

Ambocythere sp. 3057 | | . Turnover Z

Cytheropteron sp. 2914 | | il g g

Krithe sp. 6 | | | o g

Krithe sp. 19 | | | : y

Krithe sp. 7 | | | j

WEDS) | | Ss Tous 155 2-05 3-0

Tel G9. 28 | W | | water depth, km

Indet. sp. 62 C0

Cytherella serratula | RC es em

Cytheropteron cronini | es ital a a

Parakrithe sp. 10 ey

Cytheropteron sp. 2909 a

Echinocythereis whatleyi es a a ey

Rugocythereis horridus pS OO ADs | Hee Si pee a

Krithe sp. 8 2s ay, !

?Bradleya sp. 56 * -———_ l l

Bythocypris sp. 42 * i l l 8 = patie fea

Krithe spaiularis ar ia l

Krithe capensis — l l

Buntonia rosenteldi a

Buntonia sp. 34 * ss | l

Henryhowella melobesioides

Xestoleberis sp. nov. x | |

(0) 1 water depth, .km 4

Fig. 53. Depth range chart for Quaternary deep-water ostracods off south-western Africa. Inset

shows turnover of appearances and extinctions (events) summed for 100 m intervals with bars

centred on the median 50 m depth.

”

on =)

ao) a AS

— oO = - o

=) oO re

5 = ® o =

o a = > 2 — co c

= 5 @) a © a] >

‘= - 2 © t o o o 2) Be

o rs) ° a a wo € c o 5 o o

” wt o ry a Oo) o x . oe

i ee tes Ge) oS Gg 2B & BB ®

ae 2 ° o nN a o o = ie o o © © o

=- o o © N © Ce = = © ro) er Qa a = xo

= 5 io eS

SP 8B S FR g 2 S&S & 8 g ® eS ss

o 5 5 = € 2 8 So] = 5 o © ) ° 9°

en ar a A et ONS re re eye

5 = Ww Q © c rr = o c fe = = = 5 ic

> > o c c > o > ® 3 c c c °

6) re) ) a = = iva) x a S a5 a x x x a w

5) NERITIC

95 oes

BATHYAL

1000

1050

appear disappear continue

Fig. 54. Depth ranges for species at the Neritic/Bathyal Zone boundary.

depth is also suggested by changes in the abundances of three diagnostic ostracod

groups that dominate the deep-water populations (Henryhowella melobesioides,

Krithe spp., and Buntonia rosenfeldi—referred to as the HKB assemblage)

DEEP-WATER QUATERNARY OSTRACODA Baill

eis ho

Krithe sp. 22

Dutoitella suhmi

Abyssocythere australis

Krithe peypouqueti

Trachyleberis sp. 3017

Krithe sp.4

Krithe sp.7

Krithe sp.6

Krithe sp.19

Echinocythereis whatleyi

Rugocyther

Ambocythere sp.3057

Cytherella serratula

Cytheropteron cronini

Krithe rex

Henryhowella melobesioides

Cytherella sp. 3027

Cytheropteron sp. 2914

Buntonia rosenfeldi

Poseidonamicus major

STATION No.

3354

me __ _ BATHYAL

ABYSSAL

6851

6852

appear disappear

Fig. 55. Depth ranges for species at the Bathyal/Abyssal Zone boundary.

(Fig. 56): the commencement of a sharp decline into deeper water in the abun-

dance of H. melobesioides; the temporary reversal of the abundances of Krithe

spp. and B. rosenfeldi relative to each other; and a sharp decline into deeper

water in the combined abundance of all three taxa.

The faunal change between 2 000 m and 2 100 m, in fact, relates to one

sample (TBD 3355) at 2 070 m, but the size in turnover in the fauna that is

defined by this point (8 events), coupled with the apparently coincidental extinc-

tion of Buntonia rosenfeldi and the appearance of Poseidonamicus major,

indicate that a major shift in the character of the ostracod population occurs at

approximately this level. Thirteen species probably appear or disappear in the

1 200 m interval straddling this depth (Fig. 55), so we nominally take the

location of this sample to mark the depth of the boundary between the bathyal

and abyssal ostracod assemblages.

The faunal changes that are represented on the inset in Figure 53 by a

cluster of turnover events between 1 300 m and 1 700 m are accompanied by a

dramatic alteration in the character of the HKB assemblage (Fig. 56). Across

this zone, the previously dominant taxon (H. melobesioides) rapidly declines in

abundance from more than 85 per cent to c. 30 per cent of the total ostracod

population, whereas Krithe spp. progressively, and B. rosenfeldi temporarily,

become more important. In addition, the contribution to the total ostracod

population of the HKB assemblage declines across this zone from more than

95 per cent to c. 70 per cent. We nominally take the point at which

H. melobesioides ceases to be dominant to mark the boundary between these

upper and lower bathyal assemblages, viz. 1 500 m.

The vertical changes in the physical properties of the water column off

south-western Africa have briefly been mentioned in the introduction, and are

332 ANNALS OF THE SOUTH AFRICAN MUSEUM

shown in Figure 2. On Figure 56 they have been related to the ostracod distri-

butions, and it is suggested that the important faunal changes described above

can be directly correlated with the boundaries between and within the major

water masses. Shannon (1966, 1985, figs 11, 12) has plotted the vertical limits of

the low salinity zone within the AAIW and, although these fluctuate slightly

with latitude, the base lies at approximately 1 000 m. This is close to the depth

at which we have located an important change in the composition of the ostra-

cod fauna (950 m), and consequently we suspect that the level of the neritic/

bathyal faunal boundary is controlled by the depth of the base of the low salinity

zone within the AAIW.

The AAIW is underlain by southward-flowing, low-temperature, high-salinity

NADW, and the boundary between these two major water masses lies at

approximately 1500 m off south-western Africa (Shannon 1985). This level

coincides with the depth at which we have identified important changes in the

HKB assemblage, and consequently we suspect that the level of the the upper/

lower bathyal faunal boundary is controlled by the depth of the AATIW/NADW

shear zone.

Within the NADW mass, Shannon (1985) has located the core at between

2km and 3 km water depth, and we suggest that the bathyal/abyssal faunal

boundary coincides with the top of this zone.

In the Cape Basin, Antarctic Bottom Water (AABW) lies below the

NADW in water depths greater than about 4 km (Shannon 1985). It is colder

and less saline than the overlying water mass, and its higher dissolved CO:

values and relatively vigorous circulation are corrosive to carbonate valves

(e.g. Tucholke & Embley 1984). The top of the AABW forms the carbonate

lysocline, across which the calcareous skeletons of dead organisms are progress-

ively more rapidly dissolved with increasing depth. This is an ‘aggressive’

physico-chemical environment but, because we have only one sample from

below this level (TBD 6852: 4 736 m), we have insufficient data to establish if it

coincides with a further change in the ostracod fauna. Certainly, the dead fauna

was sparse and poorly preserved but we have no data on the living fauna.

Table 8 summarizes the physical properties of the three major water masses

mentioned above.

Fig. 56. Variations in the abundances of the HKB ostracod assemblage (as % total ostracod

fauna) from neritic to abyssal depths. Data are five point running means. Triangles (upper

curve) = total assemblage; squares = Krithe spp.; diamonds = Henryhowella melobesioides;

crosses = Buntonia rosenfeldi. Lower part of the diagram correlates aspects of the abundance

curves with various water mass properties. Zone over which H. melobesioides is more than

50 per cent of total ostracod fauna is stippled, and the depths at which it dominates the HKB

assemblage are shown as black bars. SMZ = salinity minimum zone; AAIW = Antarctic Inter-

mediate Water mass; NADW = North Atlantic Deep Water mass.

water

-masses ®

Henryhowella

DEEP-WATER QUATERNARY OSTRACODA 333

UPPER LOWER

NERITIC BATHYAL BATHYAL ABYSSAL

100

Henryhowella

ae melobesioides

Buntonia

7 rosenfeldi

water depth, km

NERITIC U. BATHYAL L. BATHYAL ABYSSAL

ixed

ayes AAIW NADW

melobesioides

| A | steady increase

Krithe spp. {

; I | | |

eer { | steady decline

' Combined In20 461 B76 o1 8 7 | 6 5

| | | 9

' Henryhowella ; : f |

| Krithe spp. | I |

! Buntonia em i a | mixed assemblage

NERITIC U. BATHYAL L. BATHYAL ABYSSAL

@ data from Shannon 1985 p.124-125 = sharp increase

= salinity minimum zone sharp decline

SMZ

CORE

| | = H. melobesioides dominant

= core of NADW = peak

= low

AAIW = Antarctic Intermediate water mass

NADW = North Atlantic Deep water mass

x10%

334 ANNALS OF THE SOUTH AFRICAN MUSEUM

TABLE 7

Summary of changes at faunal boundaries.

Species Depth (m)

Upper limit of Upper Bathyal Zone (950 m)

Appearance of: Parakrithe sp. 10 945

Cytheropteron sp. 2909 945

Cytheropteron cronini 990

Cytherella serratula 1 000

Indeterminate sp. 23 1 050

Indeterminate sp. 62 1 026

Disappearance of: Buntonia sp. 34 1 050

Xestoleberis sp. nov. 1 000

Bythocypnis sp. 42 1 000

?Bradleya sp. 56A 945

Upper limit of Lower Bathyal Zone (1 500 m)

Appearance of: Krithe sp. 7 1 600

Krithe sp. 4 1 600

Krithe sp. 6 1 662

Krithe sp. 19 1 662

Disappearance of: Krithe capensis 1 430

Krithe spatulanis 1 662

Upper limit of Abyssal Zone (2 070 m)

Appearance of: Poseidonamicus major 2 070

Dutoitella suhmi 2916

Trachyleberis sp. 3017 2 916

Abyssocythere australis 2916

Krithe sp. 22 2916

Krithe peypouqueti 2 916

Krithe rex 2916

Cytherella sp. 3027 2 916

Disappearance of: Cytherella serratula 2 070

Cytheropteron cronini 2 070

Cytheropteron sp. 2914 2 070

Buntonia rosenfeldi 2 070

Ambocythere sp. 3057 2 070

TABLE 8

South-eastern Atlantic deep-water masses. (Data from Shannon 1985.)

Water mass Depth Temperature Salinity Direction*

(km) (°C) (P70)

Antarctic Intermediate Water (AAIW) — 0,2—1,5 11-6 34,7-34,3 NW

Salinity minimum zone 0,6—-1,0 SAS)

North Atlantic Deep Water (NADW) LS=40 Ot 34,93—34,87 SE

Antarctic Bottom Water (AABW) >4,0) 11-5) <34,77 SE

* direction of flow off south-western Africa.

DEEP-WATER QUATERNARY OSTRACODA 335

BATHYAL FAUNAS

A total of 20 ostracod species has been identified from the Bathyal Zone off

south-western Africa, three of which are neritic species at the limits of their

depth ranges (Table 9A, Fig. 54).

The fauna of this zone (950-2 070m) can be considered transitional

between the taxonomically diverse (at least 120 species), but geographically

endemic, neritic faunas of the continental shelf and upper slope, and the taxono-

mically relatively restricted (17 species), but cosmopolitan, faunas of abyssal

depths. Only eight species are restricted to the Bathyal Zone (Fig. 53) and, of

these, five (Ambocythere sp. 3057, Cytheropteron sp. 2914, Cytheropteron

sp. 2909, and Indet. spp. 23 and 62) occur at the limits, leaving three species

only that range between the base of the AAIW salinity minimum zone and the

AAIW/NADW shear zone: Cytherella serratula, Cytheropteron cronini, and

Parakrithe sp. 10. In addition, these eight species constitute only 7 per cent of

the total bathyal ostracod population. Consequently, the bulk of the fauna is

composed of species that range into the over- and underlying zones. Neverthe-

less, the composition of the fauna of the Bathyal Zone is sufficiently different to

distinguish it as an identifiable population that has similarity indices of only

30 per cent and c. 10 per cent with the abyssal and neritic faunas, respectively.

Throughout the Bathyal Zone the HKB assemblage constitutes a minimum

of 65 per cent of the ostracod fauna, and over most of the depth range this figure

exceeds 70 per cent (Fig. 56). The individual categories are dominated by

Henryhowella melobesioides (61%), with Krithe spp. (13%) and Buntonia

rosenfeldi (9%) in relatively minor roles (Fig. 57A), but these mean values mask

fluctuations across the zone that indicate an important subdivision into upper

and lower populations. This change occurs at approximately 1 500 m, above

which the total HKB assemblage typically constitutes more than 80 per cent of

the fauna and is dominated by H. melobesioides (>70%), and below which the

HKB assemblage constitutes less than 80 per cent of the fauna and its three con-

stituent taxa are more equally mixed. As we will discuss later, these faunal

changes can be correlated with alterations in environmental parameters that

define the Upper and Lower Bathyal zones.

The most diverse genus within the Bathyal Zone is Krithe, with seven

species, but no individual species ranges throughout the zone and there is a

marked faunal discontinuity within the genus at the Upper/Lower Bathyal Zone

boundary.

UPPER BATHYAL ZONE

Sixteen ostracod species occur within the Upper Bathyal Zone but three of

these are stragglers from the Neritic Zone (Table 9A, Fig. 54). Of the

13 bathyal species, nine (representing 82% of the total fauna) are forms that

also occur in shallower depths.

The ostracod faunas of this zone are numerically dominated by the three

taxa of the HKB assemblage (Figs 56, 57B). Although together they typically

336 ANNALS OF THE SOUTH AFRICAN MUSEUM

TABLE 9

Percentage composition of fauna at bathyal and abyssal depths.

U Lower overall

A. Bathyal Zone (950-2 070 m) (950-1 500) (1500-2 070)

Yo %o

(4)

NWP ON

Henryhowella melobesioides #* 31 6

Buntonia rosenfeldi #

Krithe sp. 8 #

Echinocythereis whatleyi #*

Cytherella serratula

Rugocythereis horridus #*

Krithe capensis #

Parakrithe sp. 10

Krithe spatularis #

Cytheropteron cronini

Cytheropteron sp. 2909

Indeterminate sp. 23

Indeterminate sp. 62

Indeterminate fragments

Krithe sp. 4

Krithe sp. 6

Krithe sp. 7

Krithe sp. 19

Ambocythere sp. 3057

Cytheropteron sp. 2914

Poseidonamicus major *

Total for Krithe spp.

Neritic forms (at lower limit of their depth range)

| pe OP Ree

—

oF EP Ge Ge

—_

YJ FP OORrROOCRrR ORR OR RP RPP NWARWOH

—

Buntonia sp. 34 8

Xestoleberis sp. 35 1 =

Bythocypnis sp. 42 1

=~)

B. Abyssal Zone (051 aay

% % Krithe

Poseidonamicus major ef 29

Krithe rex

Krithe peypouqueti

Henryhowella melobesioides sd

Dutoitella suhmi

Abyssocythere australis

Knithe sp. 4

Krithe sp. 7

Krithe sp. 6

Krithe sp. 19

Krithe sp. 22

Indeterminate Krithe

Total Krithe spp. 4

Rugocythereis horridus -

Echinocythereis whatleyi -

Trachyleberis sp. 3017

Bradleya sp. 56

Cytherella sp. 3027

Indeterminate fragment

me wy Ge Gy

—_

SOR RB SB NAYNWNDBUMNAADADAD WW

— ja

17 species, 354 valves, diversity of 5 per cent

* = common to bathyal and abyssal faunas; # = common to bathyal and neritic faunas

Note: Percentages are based on total number of valves per zone, and not merely the

number of valves in those samples in which a particular species occurs.

DEEP-WATER QUATERNARY OSTRACODA 337

Bathyal fauna (950 — 2070m)

neritic

species

| )

0 WAAL aes Iles = DA

123 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

bathyal fauna (950 —1500m)

neritic

0 A Nialictee a J sae

12 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Lower bathyal fauna (1500—2070m)

;

Fig. 57. Species histograms (percentage of total ostracod fauna) for whole Bathyal (A), Upper

Bathyal (B), and Lower Bathyal (C) zones. Species identification: 1— Henryhowella melobe-

sioides; 2—Buntonia rosenfeldi,; 3— Krithe sp.8; 4—Echinocythereis whatleyi; 5—Cytherella

serratula, 6—Rugocythereis horridus; 7—Krithe capensis; 8—Parakrithe sp. 10; 9—Krithe

spatularis,; 10—Cytheropteron cronini; 11—Cytheropteron sp. 2909; 12—Indeterminate

species; 13—Krithe sp. 4; 14—Krithe sp. 6; 15—Krithe sp. 7; 16— Krithe sp. 19; 17—Ambo-

cythere sp. 3057; 18—Cytheropteron sp. 2914; 19—Poseidonamicus major; 20—total Krithe

spp.; 21— Buntonia sp. 34; 22— Xestoleberis sp. nov.; 23—Bythocypris sp. 42.

338 ANNALS OF THE SOUTH AFRICAN MUSEUM

constitute more than 80 per cent of the population, there is considerable

variation across the zone from less than 70 per cent immediately below the

upper boundary, to more than 90 per cent at 1,2 km and 1,45 km. These fluctu-

ations, to a large extent, reflect the changes in abundance of Henryhowella

melobesioides, which is the dominant taxon in the Upper Bathyal Zone. This

species becomes progressively more abundant with increasing depth down the

continental slope and reaches a peak (c. 75%) within the salinity minimum zone

at the base of the Neritic Zone. It suffers a sharp, but temporary, decline at the

top of the Upper Bathyal Zone but, with increasing depth, has a second

abundance peak between 1 200 m and 1 300 m (>80%). Below this depth its

importance rapidly declines, particularly across the Upper/Lower Bathyal

boundary.

Both Krithe spp. (6%) and Buntonia rosenfeldi (8%) are relatively minor

components of the HKB assemblage in the Upper Bathyal Zone, in terms of

overall abundance (Fig. 57B), but at particular depths are temporarily more

abundant, where they respond to certain environmental factors. In the case of

B. rosenfeldi, this occurs across the Upper/Lower Bathyal boundary (and in the

salinity minimum zone at the base of the Neritic Zone), whereas Krithe species

become more abundant immediately below the base of the salinity minimum

zone in the AATIW (Fig. 56).

The three species of Krithe that occur within the Upper Bathyal Zone

(Upper Krithe Fauna) are all inherited from the overlying Neritic Zone (Figs 11,

13, 53). Their variations in relative abundance can be correlated with changes in

environmental parameters (see next section), and allow a zonation of the Upper

Bathyal Zone. Krithe capensis is the dominant species within the Neritic Zone

but rapidly declines in abundance across the Neritic/Bathyal boundary, below

which it is replaced by Krithe sp. 8. The latter in turn is replaced by K. spatularis

in depths greater than approximately 1 000 m. Of the three Upper Bathyal Zone

species of Krithe, only K. spatularis extends across the AAIW/NADW shear

zone into the Lower Bathyal Zone, but it dies out near the top, where it is

replaced by the four species of the Lower Krithe Fauna.

Within the minor elements of the bathyal ostracod fauna, several species

appear near the top of the Bathyal Zone, although only three have an extended

range into deeper water, and of these only Parakrithe sp. 10 is confined to the

Upper Bathyal Zone. Cytherella serratula is the sole representative of the genus

within the Bathyal Zone, and is only relatively abundant either side of the

Upper/Lower boundary, where it appears to favour the unstable physico-

chemical environments associated with the shear zone. Across the continental

margin off south-western Africa, the genus Cytheropteron is as diverse as Krithe

(12 spp.), but the majority of its species are confined to the shelf and upper

slope (see Fig. 8). Deep-water representatives are confined to three species, but

only Cytheropteron cronini has been found over a wide depth range. Finally,

Echinocythereis whatleyi and Rugocythereis horridus are both characteristic

members of the Upper Bathyal Zone fauna and, although the latter has its

DEEP-WATER QUATERNARY OSTRACODA 339

highest abundance within this zone, neither is numerically important, except

within individual samples.

LOWER BATHYAL ZONE

Fourteen species have been recovered from the Lower Bathyal Zone, 50 per

cent of which extend into the Upper Bathyal Zone, 57 per cent extend into the

Abyssal Zone, and 36 per cent extend into the Neritic Zone (Tables 9, 10). The

character of the Lower Bathyal Zone fauna contrasts strongly with that of the

Upper Bathyal Zone fauna by having a mixed Henryhowella melobesioides/

Krithe spp./Buntonia rosenfeldi assemblage, as opposed to one dominated by

H. melobesioides (Figs 56, 57C). In terms of total specimens recovered from the

Lower Bathyal Zone, H. melobesioides is the most important species (31%) but,

except for isolated samples, it is subordinate in abundance to one or other of the

two other taxa. In addition, with increasing water depth H. melobesioides

becomes progressively less important, whereas Krithe species steadily become

more abundant and diverse (Figs 11, 13), with the appearance of four species in

the top part of the zone. Including K. spatularis, which extends downwards

from the Upper Bathyal Zone, 36 per cent of the species recorded from the

Lower Bathyal Zone belong to the genus Krithe. The most abundant of these is

Krithe sp. 4.

Buntonia rosenfeldi occupies a transitional position in the switch from

H. melobesioides to Krithe spp. dominated faunas at the Upper/Lower Bathyal

Zone boundary, by temporary increases in abundance at water depths where

H. melobesioides declines but where Krithe spp. do not expand to fill the

environmental niches. This opportunistic expansion is also displayed by

Echinocythereis whatleyi and to a lesser extent by Cytherella serratula, both of

which show marked increases in abundance at approximately the same levels as

B. rosenfeldi.

The depth at which we nominally take the Lower Bathyal/Abyssal Zone

boundary (2 070 m) coincides with our first record of the species Poseidonamicus

major, which is the link to the typical abyssal assemblage in sample TBD 6581.

This is also the deepest occurrence of several of the bathyal species— Buntonia

rosenfeldi, Cytherella serratula, and Cytheropteron cronini—and the sole record

of two rare taxa, Ambocythere sp. 3057 and Cytheropteron sp. 2914.

ABYSSAL FAUNAS

It is in the Abyssal Zone that the true deep-water, cosmopolitan ostracod

faunas are encountered. The character of the population is markedly different

from that found in the Bathyal Zone and the fauna is dominated by various

species of the genus Krithe (8 species), which combined comprise 47 per cent of

the ostracod population in our largest sample (TBD 6851, 2 916 m, 354 valves).

The most abundant single species are Poseidonamicus major (29%) and Krithe

peypouqueti (13%), with the overall importance of the HKB assemblage within

the total ostracod population showing a steady decline from the upper part of

340 ANNALS OF THE SOUTH AFRICAN MUSEUM

TABLE 10

Comparison of Upper Bathyal, Lower Bathyal and Abyssal faunas.

A. SIMILARITY

Upper Bathyal* Lower Bathyal Abyssal

20 species, 7 common 24 species, 8 common

similarity = 35% similarity = 33%

Bathyal Abyssal

20 species 17 species

27 species, 8 common

similarity = 30%

ates =e No. species common to both units

Similarity Total no. different species in both units nD

common

species x 100

* — values do not include the three neritic taxa

B. PERCENTAGE SPECIES COMMON

Abyssal Lower Upper

ee $

Bathyal Bathyal Namie

Abyssal

Lower 57 2 50 36

Bathyal

Upper =

Bathyal 23 54 69

Neritic®

* = No. of neritic species taken as 120 (unpublished data).

Examples:

What percentage of Upper Bathyal species occur in the Lower Bathyal Zone? ...54

What percentage of Lower Bathyal species occur in the Upper Bathyal Zone? ...50

the Abyssal Zone (65% at 2 070 m) into deeper water (50% at 2 916 m), in

which depths Buntonia rosenfeldi does not occur.

Forty-seven per cent of the abyssal species are endemic to the Abyssal

Zone, which contrasts strongly with 31 per cent and 14 per cent endemism for

DEEP-WATER QUATERNARY OSTRACODA 341

the Upper and Lower Bathyal Zones, respectively. In addition, several of the

genera do not presently occur in the shallower zones off south-western Africa:

Trachyleberis (? = Legitimocythere), Abyssocythere, and Dutoitella. All of the

Krithe species that comprise the Lower Krithe Fauna, and which appear beneath

the AAIW/NADW boundary in the Lower Bathyal Zone, persist into the

Abyssal Zone, but they are subordinate in abundance to the abyssal endemic

K. peypouqueti. Rugocythereis horridus and Echinocythereis whatleyi also occur

in the Abyssal Zone but form only minor elements of the overall population

(2% and 1%, respectively).

Our deepest sample (TBD 6852, 4 736 m) lies beneath the carbonate com-

pensation depth, and contains a sparse fauna of Krithe peypouqueti and

Trachyleberis sp. 3017 that shows signs of dissolution. This is the only record we

have of the ostracod fauna within the AABW mass, which is such an important

feature of the circulation in the Cape Basin and has vigorously scoured or main-

tained an omission surface in the region since at least late Miocene time

(Embley & Tucholke 1984; Dingle et al. 1987). Preservation of the shallower

assemblages within the overlying NADW is generally good.

SEDIMENTARY AND OCEANOGRAPHIC ENVIRONMENTS

The studies of Rosenfeld & Bein (1978), Cronin (1983), and Benson et al.

(1983) on the ostracod faunas of the continental margins off north-western

Africa and eastern North America, suggest that variations in dissolved oxygen,

salinity, and temperature are the main factors in determining the water-depth

ranges of individual deep-sea species. We will assess the influence of these

parameters on the faunas off south-western Africa, and then briefly compare our

results with their work.

OSTRACOD ABUNDANCE AND WATER DEPTH

The only physical parameter that is directly linked to water depth is hydro-

static pressure. All other factors that are likely to limit the vertical distribution

of ostracods (e.g. temperature, salinity, dissolved O2 and CO2, nutrients, light,

substrate, etc.) vary with depth only through a general vertical zonation imposed

by the structure of the water column. Nevertheless, within any area, the latter

phenomenon will maintain a relatively steady-state depth-related population

structure that allows a vertical zonation based on either assemblages or individual

species. Projecting such depth-zonations to other areas must, by definition,

be attempted with caution. Murray (1973: 168) discussed the same problem in

relation to benthic foraminifera and concluded ‘. . . that depth zones recognized

in one area on the basis of certain indicator species are only applicable to that

area and to adjacent areas where the environmental conditions are essentially

the same’. However, because globally there are fundamental similarities in the

vertical structuring of the deep water masses, a similar, relative depth-related

succession of ostracod taxa can be anticipated world-wide.

342 ANNALS OF THE SOUTH AFRICAN MUSEUM

Figure 58A shows the variation in abundance of ostracods (measured as

number of valves per 100g of the original, dry sediment sample) on the

continental margin off south-western Africa. The highest abundances

(>500 valves/100 g) all lie on the continental shelf (<220 m water depth, above

the thermocline), with the majority of sites on the slope containing less than

100 valves/100 g (mean = 29). There is a cluster of higher values (>100) either

side of 400 m water depth, and a further ‘peak’ (up to 230 valves/100 g;

mean = 98) at the base of the AAIW salinity minimum zone (Neritic/Bathyal

Zone boundary). Otherwise, maximum values for the Upper Bathyal Zone lie

between 40 and 50 valves/100 g (mean = 24) (Fig. 58B). Between 1 450 m and

1500 m, immediately above the AAIW/NADW shear zone (i.e. the Upper/

Lower Bathyal boundary), values drop to less than 10 valves/100 g, and recover

only to 15-20 valves/100 g between this level and our deepest data point at

1 780 m.

These data suggest that there is no relationship between variation in ostra-

cod abundance and water depth, but there is strong correlation between

variations in abundance and structure of the water masses.

OSTRACOD ABUNDANCE AND MUD CONTENT OF SEDIMENTS

The mud (silt and clay: <63 micron) content of 218 sediment samples from

the continental margin off south-western Africa is plotted against water depth in

Figure 59. There is a general increase in the mud content of sediments with

increasing depth from the continental shelf to 1 km, both in terms of number of

samples with more than 50 per cent mud content, and in mean percentage mud.

However, although the former parameter maintains a value of more than 90 per

cent in depths greater than 1 km, the mean percentage mud content of the sedi-

ments reaches a high of 84 per cent at 1 km, but decreases slightly farther

downslope (to 80% at 1,7 km). Mean percentage mud values for the various

zones are: Neritic—49 per cent; Upper Bathyal—82 per cent, Lower Bathyal—

82 per cent.

A comparison of Figures 58A—B (details of the mean percentage mud and

ostracod abundance for the Bathyal Zone), 59 and 60 (scattergrams of percent-

age mud plotted against ostracod abundance as valves/100g), reveals the

following trends:

1. Ostracod abundances on the continental margin off south-western Africa are

greatest (>500 valves/100 g) on the mid to outer continental shelf (150-220 m

water depth). Although the mean mud content of the sediments in this depth

range is less than 50 per cent, all the samples with abundances greater than

300 valves/100 g occur in samples with a mud content of more than 50 per cent.

This indicates that the mud content of the shelf samples is very variable but that

ostracods are most abundant in muddy samples, with maximum populations (up

to 1 900 valves/100 g) occurring in sediments with mud contents between 75 and

90 per cent (Fig. 60A). Until we have studied these faunas in detail, we cannot

comment on the specific diversity of such populations.

DEEP-WATER QUATERNARY OSTRACODA 343

(<b)

£ NERITIC U. BATHYAL

= 1000 high abundances

2. i continental

2 shelf

(7p)

3 high at base

Je SMZ

water depth, km

means | 58 (491| 21 les ae 8 |

U. BATHYAL L. BATHYAL

% mud

peak at base of

SMZ of AAIW

% mud & valves/100g

low at AAIW/

valves/100g ee boundary

water depth, km

Fig. 58. Relationship between ostracod abundance, water depth, and mud content of sedi-

ments. A. Abundance of ostracods (number of valves per 100 g of dry, unprocessed sediment)

plotted against sample depth (number of samples = 101). Mean values for various depth ranges

are recorded below the horizontal axis. The rectangular block in the lower right corner outlines

the data field used in Fig. 58B. B. Percentage mud and number of ostracod valves/100 g (both

five point running means) plotted against water depth in the Upper and Lower Bathyal zones.

Mud values are from Fig. 59, valve numbers from Fig. 58A. N.B. Values on the vertical axis

refer to ‘% mud’ and ‘valves/100 g’.

344 ANNALS OF THE SOUTH AFRICAN MUSEUM

100

UPPER

NERITIC BATHYAL BATHYAL

water depth, km

Fig. 59. Variation of mud content (silt and clay) with water depth for 218 sediment samples

from the continental margin of south-western Africa. The two curves plot data summed over

200 m intervals: circles = % of samples which have mud values >50%; triangles = mean %

mud: values are plotted at median depth point (e.g. data for the 0-200 m interval are plotted at

100 m level). Mud values are from Birch (1975), Rogers (1977) and Bremner (1981).

2. On the upper continental slope (water depths between 223 m and 900 m), the

mean ostracod abundance is 29 valves/100 g, whereas the mean mud content

steadily increases to more than 70 per cent, so that in this region the sympathetic

relationship between high mud values and high population numbers that we

detect on the shelf does not hold.

3. At the base of the salinity minimum zone (SMZ)/bathyal thermocline of

the AAIW mass (i.e. at the Neritic/Upper Bathyal Zone boundary), there is

a narrow zone (c. 950-1050 m) of high ostracod abundance (mean =

98 valves/100 g). The mean percentage mud value for the 800-1 000 m interval

is 74 per cent, but where it rises to 85 per cent in the underlying 200 m wide

sector, the ostracod abundances decline significantly (mean = 24 valves/100 g—

Fig. 58B). A further decline in abundance occurs in the lowermost Upper

Bathyal and Lower Bathyal zones (mean = 8), whereas in the same interval the

mean mud values decline slightly (84-77%, and in detail hover around a plateau

of about 80%). In general, therefore, although the mud content of the Bathyal

Zone sediments is high (>80%—Fig. 60), the ostracod abundances are low

overall (<40 valves/100 g), and even the larger populations are relatively small

in comparison with those on the continental shelf.

DEEP-WATER QUATERNARY OSTRACODA 345

all samples

0 —1800m

valves/ 100g

ro)

deep—water samples

200 900 — 1800m

valves/100g

% mud

Fig. 60. Number of ostracod valves/100 g plotted against mud content of sample. The total

ostracod fauna has been used. A. Samples from a water depth range of 0-1 800 m. The rectan-

gular block in the lower right corner outlines the data field used in Fig. 60B. B. Samples from a

water depth range of 900-1 800 m.

Taken together, the data on total ostracod population abundances in

relation to water depth and mud content of sediments suggest that, in water

depths greater than approximately 200 m, variations in overall abundance are

not directly related to the mud content of the sea-floor sediments but are con-

trolled by the structure of the water column. In as much as changes in the water

346 ANNALS OF THE SOUTH AFRICAN MUSEUM

column will also influence the mud content of the sediments, locally there is a

sympathetic relationship in alterations in mud content and overall ostracod

abundance. On the continental shelf (above the thermocline and within the

influence of surface currents), there is a direct correlation between mud

content and total population abundance, but this is a topic we will address in a

later contribution on the shallow-water faunas.

_ The above observations are based on data that monitor variations in the

total ostracod population, but these may mask correlations for individual

species. In Figure 61A—C, we have plotted the abundance (as percentage total

ostracod population) against mud content of sediments for the three taxa in the

HKB assemblage and, in Figure 61D, have summarized the percentage of

records for each species that occurs in successive 20 per cent mud categories.

From these data, we conclude that all three taxa have a preference for sediments

with a mud content of more than 50 per cent but that the occurrences of Henry-

howella melobesioides and Krithe spp. are more mud-specific (57% and 55% of

records occur in sediments with >60% mud, respectively) than Buntonia rosen-

feldi (48%). However, the latter has a lower tolerance of low mud contents. We

did not record Buntonia rosenfeldi in sediments with less than 20 per cent mud,

whereas 7 per cent and 3 per cent respectively of occurrences of H. melo-

besioides and Krithe spp. were within this category. Further, B. rosenfeldi

appears to tolerate mud contents of more than 85 per cent less well than either

of the other two species. Its abundance (as percentage of total ostracod popu-

lation) in this category is never more than 25 per cent, whereas in very muddy

sediments both H. melobesioides and Krithe spp. are frequently the dominant

taxa. This is especially the case with H. melobesioides.

From this brief survey we can conclude that, although the abundance of the

overall ostracod population is less influenced by the mud content of the bottom

sediments than by factors associated with the ambient water mass, individual

species are so influenced.

OCEANOGRAPHIC FACTORS

Figure 62 summarizes the vertical changes in dissolved oxygen, salinity, and

temperature in transects across the continental margin off south-western Africa.

Using these profiles in conjunction with the vertical distribution of selected

ostracod taxa (Fig. 63) and variations in the composition of the overall fauna

(Figs 53, 56), we can assess the effectiveness of vertical changes in the physico-

chemical properties of the water column as barriers to ostracod distribution, and

hence the maintenance of the composition of the faunas of the various depth

zones.

On the continental shelf, temperature and salinity values are relatively high

(>12°C and >34,9%o, respectively) and sediment textures variable. In addition,

the pattern of dissolved oxygen values is complicated, with a single minimum

zone in the south (Stander 1964), and a double minimum in the north (Chapman

& Shannon 1985), with the result that the ostracods of this shallow zone have

DEEP-WATER QUATERNARY OSTRACODA 347

100

B. rosenfeldi

20 100

Krithe spp.

H. melobesioides

B. rosenfeldi

0 100 0) 20 40 60 80 100

% mud % mud

Fig. 61. Abundance of individual species (as % total ostracod fauna) of the HKB assemblage

plotted against mud content of samples. A. Buntonia rosenfeldi. B. Krithe spp. C. Henry-

howella melobesioides. D. Summary of variation of abundance versus percentage mud for the

three species. Values are shown as percentage of records within successive 20 per cent intervals

of mud, and have been equalized to avoid sampling bias.

a complex distribution pattern. We will be describing these faunas in a later

publication and defer further discussion of this zone until then.

The top of the AAIW mass lies at about 200 m (Shannon 1966, 1985) and is

associated with a relatively thick thermocline that is steepest between approxi-

mately 200 m and 400 m. At the top of the AAIW, water temperatures vary

348 ANNALS OF THE SOUTH AFRICAN MUSEUM

Vite layer

| AAIW NADW A ABW

shear] zone

A Sy 9, OP

Dissolved oxygen

water depth, km

34:7 ae

. }

Mi Salinity

34°3 vA

(0) ry 4

Hy water depth, km

c i

Or i)

1 Hy

5 HY

Temperature

0) 15 4

water depth, km

U. L.

NERITIC BATHYAL ABYSSAL

Fig. 62. Variations in physico-chemical parameters on the sea floor along transects off south-

western Africa. Water-column structure and faunal zones are correlated along the top and

bottom margins of the diagram, respectively. A. Dissolved oxygen (mf/€) at 20°S, 34°S, and a

composite profile between 28°S and 33,5°S (the deflection in the curve at 2,5 km is an artefact

caused by juxtaposition of data from two transects). B. Salinity (%o) at 24°S and 34°S. C. Tem-

perature (°C) at 24°S and 34°S. Constructed with data from Fuglister (1960), Stander (1964),

Bubnov (1966), Shannon & Van Rijswijk (1969), Welsh & Visser (1970), Gorshkov (1978),

Shannon (1985), and Chapman & Shannon (1985). Data points taken at 100 m intervals. Zones

have been shaded to aid correlation.

Fig. 63 (see facing page). Variations in abundance (% total ostracod population) of various

ostracod species correlated with water column barriers, and faunal zones. A—Henryhowella

melobesioides (five-point means); B—Krithe species (five-point means); C—Rugocythereis

horridus (raw data); D—Cytheropteron species (five-point means); E—Cytherella species

(five-point means); —Buntonia rosenfeldi (five-point means); G—Echinocythereis whatleyi

(three-point means).

DEEP-WATER QUATERNARY OSTRACODA

anne layer

AAIW NA DW

Ue zone

100 A Bi oa Poe z Vo

eerie Eee () H. melobesioides

a =)

core

Krithe spp.

R. horridus

(o}

Cytheropteron spp.

Cytherella spp.

percentages of total ostracod fauna

B. rosenfeldi

1 2

water depth, km

U. L.

NERITIC BATHYAL ABYSSAL

349

350 ANNALS OF THE SOUTH AFRICAN MUSEUM

from north to south between 11°C and 9°C, and these fall to c. 3,4°C at the

base. The gradient of the temperature changes is very low below 1 000 m but

increases steadily into shallower water, with the main temperature ‘break’ at

about 3,5°C. This bathyal thermocline approximately coincides with the base of

the salinity minimum zone (SMZ) at the core of the AAIW mass (Shannon

1966, 1985), which itself is a relatively low salinity body of water sandwiched

between the higher salinity continental shelf waters and the NADW mass

(Fig. 62). The lower limit of the SMZ lies at about 1 000 m along the whole of

the continental margin off south-western Africa and coincides with a dissolved

oxygen minimum zone in which values vary from 4,25 ml/I at 30°S to 3,8 ml/l at

34°S (Fig. 62A). The SMZ is thicker in the south (32°S), where the upper limit

occurs at about 500 m, in comparison with 600 m at 24°S. Minimum salinity

values in the SMZ vary from 34,36%o in the south to 34,48%c in the north. The

physico-chemical hiatus that controls the depth of the Neritic/Bathyal Zone

boundary appears, therefore, to be a combination of the bathyal thermocline

(below which the water temperature is <3,5°C), a steep increase in salinity

below the SMZ (with the ‘critical’ level around 34,50%c), and an oxygen

minimum zone.

The boundary between the AAIW and NADW masses lies at about

1 500 m off south-western Africa (Shannon 1985). There is no apparent change

in either the temperature or salinity gradients across the contact but, because

these bodies are flowing in opposite directions, there will be a relatively intense

zone of shearing across it (marked by turbulence and a sharp velocity gradient).

The slightly lower mud values detected between 1 400 m and 1 500 m (Fig. 58B)

may be related to turbulence in the lowermost part of the AAIW. Variability in

temperature, salinity and current strengths, rather than significant breaks in

their gradients, seem to be the main factors controlling the location of the

Upper/Lower Bathyal zone faunal boundary.

The core of the NADW lies between 2 000 m and 3 000 m (Shannon 1985)

and its upper boundary is marked by a sharp change in the salinity values, where

the gradient decreases rapidly and below which salinity values peak at about

34,9%o in the north and 34,86%o in the south. Below the depths at which these

peaks occur (2 000 m and 2 300 m, respectively), the salinity values decrease

very slowly. There are no accompanying temperature changes at the top of the

NADW core, so that the Bathyal/Abyssal Zone faunal boundary that is main-

tained by this feature must be related to the relatively large upslope decrease in

salinity and any water turbulence that is caused by the velocity gradient across

the top of the NADW core zone.

The NADW/AABW boundary lies at about 4 000m and is marked by

small, but significant, increases in both temperature and salinity gradients.

Because we have no ostracod-rich samples below 4 000 m, we cannot comment

on whether or not this water-mass contact causes a significant faunal hiatus.

Certainly, because the top of the AABW mass marks the upper limit of the

DEEP-WATER QUATERNARY OSTRACODA 351

carbonate lysocline, the chemical environment below this depth can be expected

to be severe.

To assess the effectiveness of these boundaries as barriers to the habitats of

various ostracod species, we have plotted the abundances of the numerically

most important species and genera against depth (Fig. 63), and can extract the

following salient points.

1. Base of salinity minimum zone/bathyal thermocline of AAITW

EFFECTIVE: Krithe spp. (including Parakrithe)—there is a decrease in

abundance of the overall population into and out of the SMZ, with a mid-

zone high. Two species turn over at lower boundary.

Cytherella spp.—very effective barrier; high abundances and number of

species in Neritic Zone do not persist across SMZ; bathyal species are

isolated by barrier.

Echinocythereis whatleyi—does not range above SMZ.

Rugocythereis horridus—does not range above SMZ.

Cytheropteron—ranges of individual species restrained by SMZ, but not

effective in altering overall population abundances, which reach a high in

the SMZ.

INEFFECTIVE: Henryhowella melobesioides—the drop in abundance at base

of SMZ may be related to a decrease in mud content.

Buntonia rosenfeldi—favours the conditions therein and reaches a minor

peak of abundance just above base of SMZ.

2. Boundary of AAIW and NADW masses (shear zone)

EFFECTIVE: Henryhowella melobesioides—very effective; dramatic decrease

of abundance into NADW.

Krithe species—very effective; dramatic increase in abundance into

NADW;; high species turnover.

Rugocythereis horridus—confines high abundances to the Upper Bathyal

Zone.

INEFFECTIVE: Buntonia rosenfeldi—reaches peak abundance in the shear

zone.

Cytherella species—C. serratula reaches maximum abundance in the shear

zone.

Echinocythereis whatleyi—reaches maximum abundance in the shear zone.

Cytheropteron species—no significant changes across this barrier.

3. Top of NADW core

EFFECTIVE: Krithe species—small abundance change across barrier, but

apparently no turnover of species.

Buntonia rosenfeldi—is severely restricted below boundary.

Cytherella species—is severely restricted below boundary.

Echinocythereis whatleyi— abundances low beneath barrier.

352 ANNALS OF THE SOUTH AFRICAN MUSEUM

Rugocythereis horridus— abundances low beneath barrier.

Cytheropteron species—C. cronini does not range below barrier.

Poseidonamicus major—does not range above barrier.

INEFFECTIVE: Henryhowella melobesioides—no_ significant change in

abundance across barrier.

Table 11 lists the barriers and the responses to them by individual species.

We can summarize the physico-chemical features of each barrier and how it

maintains the character of the various faunal zones as follows:

1. Neritic/Upper Bathyal Zone boundary (AAIW—base of SMZ/bathyal

thermocline). This barrier consists of: (a) change in temperature gradient

(‘critical’ temperature c. 3,5°C); (b) steep salinity gradient (i.e. a zone of rapid

change); and (c) oxygen low zone; and has the following effects: (a) prevents the

neritic populations of the diverse genera Cytheropteron, Buntonia, and

Cytherella from moving downslope and (b) prevents Rugocythereis horridus and

Echinocythereis whatleyi from moving upslope.

2. Upper/Lower Bathyal Zone boundary (AAIW/NADW contact and associated

shear zone). This barrier consists of turbulence, resulting in variable tempera-

TABLE 11

Summary of barrier effectiveness.

SMZ AAIW/ NADW

Approximate Temp. (°C) 4,0-3,4 3;

‘critical’ Salinity (°/,) 34,5 34,

parameters Oxygen O, low

Henryhowella melobesioides

Krithe spp. as = as

Buntonia rosenfeldi

Cytherella spp. +3 #2

Echinocythereis whatleyi oD #2

Rugocythereis horridus aD *1 me

*3 *

Cytheropteron spp.

Poseidonamicus major

* — effective barrier

moving from shallow to deeper depths, cannot tolerate:

‘ —lower temperature and higher salinity

—low temperature and high salinity

> — lower temperature and low oxygen

moving from deep to shallower depths, cannot tolerate:

a — higher temperature and lower salinity

> — higher temperature, higher salinity, and low oxygen

Ranges in ‘critical’ parameters relate to north to south variations

DEEP-WATER QUATERNARY OSTRACODA 353

tures, salinities and current strengths, and has the following effects: (a) separ-

ates the Henryhowella melobesioides-dominated Upper Bathyal fauna from the

mixed H. melobesioides/Krithe spp./Buntonia rosenfeldi Lower Bathyal fauna;

(b) limits the depth ranges of several Krithe species to produce the Upper and

Lower Krithe faunas; and (c) allows three species to opportunistically increase

their abundances— Buntonia rosenfeldi, Cytherella serratula, and Echino-

cythereis whatleyi.

3. Lower Bathyal/Abyssal Zone boundary (top of NADW core). This barrier

consists of: (a) change in salinity gradient (‘critical’ salinity c. 34,89%o in the

north and 34,86%oc in the south); and (b) ?turbulence, and has the following

effects: (a) maintains peak Krithe spp. population abundances downslope;

(b) prevents Buntonia rosenfeldi and Cytheropteron cronini from extending

farther downslope; (c) prevents Poseidonamicus major from extending farther

upslope. This regulates the upper level of a true abyssal taxon.

Finally, it is clear that, although we have been able to identify the efficiency

of these physico-chemical changes in the water column as regulators of overall

faunal character, the taxa involved react to these changes in different ways. To

some they are solid barriers and to others sieves, and it is not possible at this

stage to identify a predictable pattern.

A particularly good example of this apparently random response occurs at

the AAIW/NADW shear zone. Here, within what we can only tentatively

suggest is a narrow, turbulent layer of mixed water with variable temperatures,

salinities, and current strengths, there are relatively large increases in abun-

dances of Buntonia rosenfeldi, Cytherella serratula, and Echinocythereis what-

leyi. In this region, therefore, the combination of narrow, but unstable, temper-

ature and salinity ranges involved (3,18-3,25°C and 34,75-34,84%o in the

north, to 2,91—2,79°C and 34,68—34,73%o in the south) afford a highly favourable

ecological niche for at least three species to exploit opportunistically. At the

same time, this zone separates AAIW—in which H. melobesioides is abundant

and Krithe species relatively sparse, from NADW-—in which the roles of these

- two taxa are almost reversed. However, neither of these species finds the con-

ditions within the shear zone at all favourable. A further aspect of this complex

response can be seen in the distribution of H. melobesioides, where the portion

of the water mass in which it is most abundant (AAIW) has temperature and

salinity characteristics of 2,9-3,3°C (mean 3,1°C) and 34,65-34,68%o (mean

34,67%o), whereas the underlying water mass, which it finds so unfavourable, has

charactersitics of 2,78-3,1°C (mean 2,94°C) and 34,77-34,87%o (mean 34,82%c).

The differences involved are 0,16°C and 0,15%c, respectively, yet in the Neritic

Zone (across the upper part of the SMZ) changes in temperature and salinity

five times these values result in abundance changes only half as large.

354 ANNALS OF THE SOUTH AFRICAN MUSEUM

COMPARISON WITH RESULTS FROM OTHER AREAS

We will briefly review four recent studies on deep-water ostracod faunas in

which attempts were made to correlate distribution with various environmental

parameters, and then summarize the results in the light of our findings.

Cronin (1983) worked off the south-eastern USA but, because his survey

did not assess environmental factors below 1 100 m, his data relate primarily to

shallower depths than we have investigated. Nevertheless, there are similarities

in faunal content that make comparison relevant. Cronin found that the two

prime controls on depth ranges are the 15—8°C thermocline at 150 m, and the

oxygen minimum zone (3 ml/l) between 200-800 m. These barriers define two

main ostracod faunas: one within the O2 minimum zone, and one below it. The

latter includes some taxa similar to our bathyal faunas.

Benson et al. (1983) worked off the continental margin of north-eastern

North America. They identified three ostracod faunas (biofacies), which they

correlated with particular water masses. These faunas lie at 400-1 400 m

(Labrador Sea Water mass; Upper Slope Biofacies); 1 500—2 399 m (North East

Atlantic Deep Water mass; Transitional Biofacies); and >2 400 m (Denmark

Strait Overflow Water mass; Lower Slope and Rise Biofacies). Benson et al.

(1983) concluded that the limiting parameters are probably temperature, and

possibly salinity. No correlation was observed between sediment type or the

organic carbon content of sediments.

Rosenfeld & Bein (1978) worked off north-western Africa. Their study did

not extend to abyssal depths but, as with Cronin’s (1983) work, some similarity

with our faunas makes comparison relevant. On the north-western African

margin, there is a major faunal break on the upper slope that separates a

‘shallow-water’ (100-483 m) fauna from a ‘deep-water’ (470-2 859 m) fauna.

Rosenfeld & Bein (1978) did not discuss the nature of the environmental par-

ameters that maintain this boundary but assumed that it was temperature

controlled (i.e. it marks the top of ‘psychrosphere’). A northward elevation of

this level was attributed to local upwelling. No linkage was detected between

ostracod distribution and sediment texture.

Peypouquet & Benson (1980) compared the ostracod faunas from two

traverses in the south-eastern Atlantic (off Walvis Bay, and off northern

Angola). Their objective was to assess the role of the Walvis Ridge in limiting

the distribution of various taxa. They identified three major depth-related

faunas in the Angola Basin and two in the Cape Basin (no samples were

collected below 3 000 m in the latter), and these were correlated with major

water masses: epibathyal stage (400-1 500 m) = AAIW; mesobathyal stage

(1 500-3 000 m) = NADW,; and infrabathyal stage (3 700-4 700 m) = AABW.

They detected differences in the epibathyal and mesobathyal faunas on either

side of the Walvis Ridge, which they related to nutrient rich (particulary P and

Si), Antarctic-derived water affecting higher bathymetric levels on the southern

side of the gidge. It is the contrast in dissolved O2 values, rather than minimal

DEEP-WATER QUATERNARY OSTRACODA B55

variations in temperature and salinity, that is thought to maintain the faunal

differences between the two basins.

Temperature, salinity, and dissolved oxygen are all cited as parameters that

control the depth ranges of ostracod species, as well as regulating population

abundances and diversity. However, the four previous surveys that we have

reviewed, as well as our own results, illustrate that their roles vary from species to

species, and also vary for a given species within the water column. Peypouquet

& Benson (1980) also suggested that variations in nutrient levels and dissolved

oxygen can be responsible for major lateral taxonomic differences on a regional

scale. As barriers to vertical distribution, local high gradients in any of the

parameters we have mentioned can be expected to be limiting, and this is particu-

larly the case in relatively shallow water. Consequently, the shelf/slope

thermocline (e.g. Cronin’s 1983 data), and shelf oxygen minima (e.g. eastern

boundary upwelling systems, such as that off south-western Africa) can be

expected to constitute major faunal barriers. In deeper water, lower gradients

may not appear to have the same potential but nevertheless are equally

effective. It follows, therefore, that the deep-water taxa are less tolerant of, say,

temperature and salinity changes, or critical combinations thereof. The latter pre-

sumably must be the case for species, such as Henryhowella melobesioides, to cite

a local example, that have a wide depth range. In fact, the concept of a ‘depth

range’ is misleading because it merely reflects a range over which certain physico-

chemical parameters are tolerable. As all the studies we have cited confirm, these

tolerance ranges are governed by the characteristics of the ambient water masses.

In the deep sea, therefore, the vertical faunal zonation merely reflects the local

structure of the water column.

INTRA-OCEANIC RELATIONSHIPS

Table 12 shows the vertical distribution of key taxa from the deep-water

studies in the Atlantic Ocean. Although certain taxa are universally present and

often locally abundant, both in the lower neritic, bathyal and abyssal zones (in

particular various species of Henryhowella, Cytherella, and Krithe), there are

some regional contrasts, which can be related to differences in water-column

structure.

UPPER BATHYAL FAUNAS

Here we include ostracod populations between depths of 900-1 500 m. At

the lower level, faunal breaks have been recognized off north-eastern America

and south-western Africa (Peypouquet & Benson 1980 recorded a faunal bound-

ary at this depth off Angola, although they had no data between 650-2 000 m),

and this depth coincides with the upper limit of the NADW mass, which in the

south-eastern Atlantic is overlain by AAIW, and in the North Atlantic by the

Labrador Sea Water mass.

ANNALS OF THE SOUTH AFRICAN MUSEUM

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DEEP-WATER QUATERNARY OSTRACODA

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Depth

800

1000

Upper

Bathyal 1 200

1 400

1600

Lower

Bathyal 1800

Sooaeaaaaa 2000

2 200

2 400

2 600

2 800

Abyssal 3000

3 200

3 400

3 600

4 000

4 200

4 400

4 600

4 800

TABLE 12

Key to the Atlantic Ocean distribution of deep-water ostracod taxa.

SE North

America

Trachyleberis

Cytherella-2

TecenEes

Krithe

Henryhowella

Others-37

Macrocypns

Henryhowella

Krithe-?

Cytherella

Others-23

NE North NW Africa Angola SW Africa

America

Macrocypnis

Cytherella-?

Others-20 Cytherella-?

EEREEEEECE SES Krithe-1 Krithe-2

PRS SEER Others-4 Henryhowella

TREES SEIS Buntonia

Rugocythereis

Krithe-1 Echinocythereis

(Gy 5/727 | SS

Others-9 no data Cytherella-1

Kyithe-3

Echinocythereis

Henryhowella Rugocythereis

Krithe-2 Buntonia

Se osasoeenanaa= Echinocythereis SEER ESSEC EET CaaS oo

Buntonia Henryhowella

Cytherella-? Buntonia

Krithe-2 no data Rugocythereis

Cytherella-1 Knithe-5

WIAA eerrecerccerey 9 SEESEEEEEEIESIISD

Others-6 Kriti

Buntonia Trachyleberis

Cytherella-? Krithe-7

Trachyleberis Cytherella-1

Seon nn on nna a= Henryhowella Dutoitella

Krithe-3 Echinocythereis Poseidonamicus

Echinocythereis Rugocythereis Abyssocythere

Henryhowella Macrocypris Echinocythereis

Trachylebers Others-5 Rugocythereis

Rugocythereis. srt Henryhowella

Poseidonamicus —————————aennsysnensarsens

Cytherella-1

Macrocypris-1 no data

Dutoitella

Others-11 seeeeecerenensees

3) AV Osea Buntonia no data

Trachylebens

Henryhowella

Echinocythereis

Poseidonamicus

Dutoitella

Krithe-4

Macrocypns

Others-6

pesgsagh te — limits of survey —

=~ -— faunal boundaries

Santrerrencons —limits of data set

-(n) —no. of species

Others— miscellaneous species

Henryhowella

Others-5

Echinocythereis

Others-5

OSE

WASAW NVOINAVY HLNOS AHL JO STVNNV

Not eA ee eam SS eee

VdOOVULSO AUVNAALVNO UALVM-daaa

LSE

358 ANNALS OF THE SOUTH AFRICAN MUSEUM

With the exception of north-eastern America (which has an atypical,

low-diversity Arctic shelf fauna displaced on to the slope by the southwardly

descending Labrador Sea Water), all the areas have a moderately diverse

ostracod fauna that includes various species of the universal taxa (Krithe,

Cytherella, Henryhowella, Legitimocythere (including ‘Thalassocythere’ of

Benson), and Cytheropteron), as well as numerous more localized species that

reflect the adjacent neritic populations. The latter, as we have intimated earlier,

are strongly influenced by local oceanographic and sedimentological regimes.

Consequently, the upper bathyal faunas vary considerably on a regional scale,

whilst retaining a large degree of similarity via their universal taxa. In particular,

the abundance of Henryhowella and a relatively abundant and diverse

component of Krithe (compared to the neritic faunas) are characteristic.

The Upper Bathyal fauna off south-western Africa differs from that at the

other localities in one important respect, viz. the presence of Rugocythereis and

Echinocythereis whatleyi, and the absence of Macrocypris and Bythocypris.

LOWER BATHYAL AND ABYSSAL FAUNAS

The depth of the faunal boundary between the abyssal and lower bathyal

assemblages varies regionally, depending on the local structure of water column.

In the Cape Basin, we find a faunal break at about 2 000m marked by

the appearance of Poseidonamicus major and the disappearance of Buntonia

rosenfeldi and other species. However, because Poseidonamicus occurs on the

continental shelf off south-western Africa, its presence may not be so significant

in indicating abyssal assemblages as previously assumed, and that more typical

abyssal faunas appear with Abyssocythere, Dutoitella, and Krithe peypouqueti at

2 916m. This distribution, in fact, is very similar to that off north-eastern

America, where Benson et al. (1983) found equivalent taxa appearing over

similar depth ranges— Poseidonamicus somewhere between 1500m _ and

2 500 m, and Dutoitella (recorded as ‘Suhmicythere’) at 3 000 m. These two

areas differ from the Angola Basin, where Poseidonamicus does not occur above

3 000 m and Dutoitella (as ‘Shumicythere’ [{sic]) above 3 797 m (Peypouquet &

Benson 1980). This is probably a result of structural differences in the water

column between the Cape and Angola basins, where AABW is largely pre-

vented from intruding into the latter by the Walvis Ridge. In fact, Peypouquet

& Benson (1980) suggested that the Angola Basin has a North Atlantic aspect to

its deep-water fauna (typified by the presence of Pterygocythere mucronalatum

(Brady, 1880)), which is caused by the Walvis Ridge shielding the area from the

nutrient-rich (particularly P and Si) Antarctic-derived waters. We are not con-

vinced that this effect is significant above the 4 000 m level, because the regional

gradients in both parameters do not seem anomalous either side of the ridge

(see Gorschov 1978, figs 237D, 238A, 239C-D), and suspect that oceanic

upwelling off south-western Africa may be a more important factor.

Rosenfeld & Bein (1978) sampled the margin off north-western Africa to a

maximum depth of 2 859 m but did not record any of the typical abyssal taxa,

DEEP-WATER QUATERNARY OSTRACODA 359

although both Buntonia rosenfeldi and Echinocythereis whatleyi occur at this

depth. This indicates that the Lower Bathyal fauna extends to greater depths off

north-western Africa than either in the north-western or south-eastern Atlantic

regions, and it may be significant that the temperatures and salinities at this

depth are higher off north-western than off south-western Africa: 2,75°C,

34,94%o, and 2,53°C, 34,89%o, respectively (Fuglister 1960).

In summary, the ostracod faunas off south-western Africa display a deep-

water aspect, both in their bathyal and abyssal elements, at shallower depths

than most of the more northerly sites that have previously been investigated.

Specifically, Rugocythereis and Echinocythereis whatleyi both range into the

lowermost Neritic Zone (i.e. above 950 m), Bythocypris and Macrocypris do not

range into the Bathyal Zone, and—with the possible exception of north-eastern

North America— Poseidonamicus (2 000 m) and Dutoitella and Abyssocythere

(3 000 m) occur above their counterparts elsewhere. We attribute these differ-

ences to lower water temperatures and salinities caused by a combination of

local oceanic upwelling (Benguela system), and the area’s proximity to and ease

of access for Antarctic water masses.

CONCLUSIONS

Important changes in the vertical distribution of deep-water ostracods off

south-western Africa occur at major physico-chemical boundaries between and

within the main water masses (Table 13). The faunas between these boundaries

have the following characteristics:

1. Between the base of the SMZ/bathyal thermocline and the AAIW/NADW

boundary there is a cosmopolitan bathyal assemblage, numerically dominated by

Henryhowella melobesioides, with a diverse Krithe species fauna, together with

important Cytherella serratula, Cytheropteron cronini, Echinocythereis whatleyi,

and Rugocythereis horridus.

2. Between the AAITW/NADW boundary and the top of the NADW core the

assemblage is dominated by Krithe species, with H. melobesioides rapidly

decreasing in numbers with increasing water depth.

3. An abyssal assemblage occurs below a level near the top of the NADW core

(between 1 780 m and 2 070 m), which marks the upper depth limit of Poseidon-

amicus major.

4. At a level somewhere between 2 070 m and 2 916 m there is a further influx

of abyssal taxa: e.g. Dutoitella suhmi, Abyssocythere australis, Krithe peypou-

queti, K. rex, and Trachyleberis sp. 3017 (= Legitimocythere).

5. The AABW assemblage consists of sparse, poorly preserved Krithe sp. and

Legitimocythere.

Our data suggest that migration of taxa up- and down-slope is regulated by

physico-chemical changes in the water column acting as barriers or filters. These

have the effect of maintaining the integrity of the assemblages of the intervening

sectors of the water masses.

360 ANNALS OF THE SOUTH AFRICAN MUSEUM

TABLE 13

Summary of species distribution in faunal zones and water masses.

Upper Lower

Bathyal Bathyal

Abyssal

Depth (km)

Water masses

Trachyleberis sp. 3017

Krithe peypouqueti

Krithe rex

Cytherella sp. 3027

Krithe sp. 22

Dutoitella suhmi

Abyssocythere australis

Poseidonamicus major

Ambocythere sp. 3057

Cytheropteron sp. 2914

Krithe sp. 6

Krithe sp. 19

Krithe sp. 7

Krithe sp. 4

Cytherella serratula

Cytheropteron cronini

Echinocythereis whatleyi

Rugocythereis horridus

Buntonia rosenfeldi

Henryhowella melobesioides

Krithe spatularis

Indet. sp. 23

Indet. sp. 62

Parakrithe sp. 10

Cytheropteron sp. 2909

Krithe sp. 8

Krithe capensis

Buntonia sp. 34*

Xestoleberis sp. nov.*

?Bradleya sp. 56*

Bythocypris sp. 42*

».4

6 PS Pd DS PS PO OK OOK OD OK OPS OO OD OOK

* — neritic taxa

These observations lead to the important conclusion that the major water

masses, and important structural features within them, can be characterized by

their ostracod assemblages. This provides a potential tool for environmental and

palaeo-oceanographic investigation, and Dingle et al. (1989) have presented a

preliminary discussion of its application, based on our results from south-

western Africa. Extension of this work, involving a comparison of the Cape

Basin data with previous studies from other parts of the Atlantic, indicate that

deep-water ostracod assemblages can be used to discriminate water masses

DEEP-WATER QUATERNARY OSTRACODA 361

on an ocean-wide basis (Dingle & Lord in press.). This suggests that benthic

ostracods can be employed in a similar manner to benthic foraminifera in

palaeo-oceanographic studies, and an _ ostracod assemblage/water-mass

correlation scheme, parallel to that achieved for foraminifera by, for example,

Schnitker (1980) and Douglas & Woodroff (1981), is a foreseeable development.

Distribution and environmental studies in other oceans (e.g. Whatley &

Ayress 1988; Hartmann & Hartmann-Schroder 1988; Steineck et al. 1988)

should permit the application of a correlation scheme for deep-water ostracod

assemblages and water masses world-wide. However, direct correlation between

species and the complex relationships linking conservative (e.g. temperature and

salinity) and non-conservative (e.g. dissolved oxygen and silica) water par-

ameters will probably require considerably more effort, if the progress achieved

in foraminiferal studies is a measure of the difficulties involved.

ACKNOWLEDGEMENTS

This study was undertaken on sediment samples collected by the Marine

Geoscience Unit at the University of Cape Town. Sea-time and laboratory work

were variously funded by the University of Cape Town, South African Commit-

tee for Oceanographic Research, Foundation for Research Development,

Geological Survey of South Africa, South African Museum (RVD), Department

of Education Northern Ireland (IDB), and University College London (ARL).

We are grateful to all these benefactors, and RVD especially thanks Mike

Cluver and Brett Hendey for providing the opportunity to work in the Depart-

ment of Cenozoic Palaeontology at the SAM. In addition, we thank numerous

colleagues who assisted with sample collection and, in particular, the officers

and men of the University of Cape Town research vessel Thomas B. Davie, on

which all the field work was undertaken. We gratefully acknowledge John

Rogers at UCT for providing sediment samples TBD 6851 and 6852 from an

unpublished data set.

Professor R. C. Whatley (Aberystwyth) is thanked for his constructive

criticism of the manuscript and for his opinion on the identification of certain

taxa. Two anonymous referees also suggested important improvements to the

text. Judy Woodford is thanked for drafting the diagrams.

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GUERNET, C. 1985. Ostracodes Paleogenes de quelques sites ‘D.S.D.P.’ de Ocean Indien

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of Ostracoda: its fundamentals and applications. Proceedings of the Ninth International

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fentlichungen des Geologischen Institutes der Universitat zu K6éln 51: 1-712.

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LeRoy, D. O. & Levinson, S. A. 1974. A deep-water Pleistocene microfossil assemblage

from a well in the northern Gulf of Mexico. Micropaleontology 20 (1): 1-37.

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abschnitte. Fauna u. Flora des Golfes von Neapell 21 (1-8): 1-404.

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NEALE, J. W. 1974. On Pennyella pennyi gen. et sp. nov. Stereo-Atlas of Ostracod Shells 2 (2):

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codes des genres Krithe et Parakrithe: relation possible avec la teneur en O2 dissous dans

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DEEP-WATER QUATERNARY OSTRACODA 365

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d’Angola: distribution bathymetrique en fonction de ’hydrologie. Bulletin de l'Institut de

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sediments off Northwest Africa. ‘Meteor’ Forschungergebnisse (C, Geologie und Geophy-

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Sars, G. O. 1922-28. An account of the Crustacea of Norway. 9. Ostracoda. Bergen: Bergen

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dell’Accademia nazionale dei Lincei. Rendiconti (3) 6: 1-446.

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tional Report, Division of Sea Fisheries, South Africa 58: 1-22.

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features and processes. Oceanography and Marine Biology. An Annual Review 23:

105-182. Aberdeen: University Press.

SHANNON, L. V. & vAN Ruswisick, M. 1969. Physical oceanography of the Walvis Ridge

region. Investigational Report. Division of Sea Fisheries, South Africa 70: 1-19.

STANDER, G. H. 1964. The Benguela Current off South West Africa. Investigational Report.

Marine Research Laboratory, Administration of South West Africa 12: 1-43.

STEINECK, P. L. 1981. Upper Eocene to Middle Miocene ostracode faunas and paleo-

oceanography of the North Coastal Belt, Jamaica, West Indies. Marine Micropaleon-

tology 6 (4): 339-366.

STEINECK, P. L., BREEN, M., Nevins, N. & O’Hara, P. 1984. Middle Eocene and Oligocene

deep-sea Ostracoda from the Oceanic Formation, Barbados. Journal of Paleontology 58

(6): 1463-1496.

STEINECK, P. L., DEHLER, D., HoosE, E. M. & McCatra, D. 1988. Oligocene to Quaternary

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applications. Proceedings of the Ninth International Symposium on Ostracoda, Shizuoka,

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Swain, F. M. 1963. Pleistocene ostracoda from the Gubik Formation, Arctic coastal plain,

Alaska. Journal of Paleontology 37 (4): 798-834.

366 ANNALS OF THE SOUTH AFRICAN MUSEUM

SwaIN, F. M. 1970a. Pliocene ostracodes from deep-sea sediments in the southwest Pacific

and Indian Ocean. Jn: FUNNEL, B. M. & RIEDEL, W. R. eds. The micropalaeontology of

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land and Ireland. Part 4. Ostracoda. Professional Papers. United States Geological

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off South Africa. Memoir. American Association of Petroleum Geologists 36: 145-163.

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gebietes (Niedersachsen und Hamburg, NW-Deutsches Tertiarbecken). Palaeontographica

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Maryland. Maryland Geological Survey, Miocene Report: 98-130.

WELSH, J. G. & Visser, G. A. 1970. Hydrological observations in the South-East Atlantic

Ocean. Investigational Report. Division of Sea Fisheries, South Africa 83: 1-24.

WHATLEY, R. C. 1983. Some aspects of the palaeobiology of Tertiary deep-sea Ostracoda

from the S.W. Pacific. Journal of Micropalaeontology 2: 83-104.

WuatTLey, R. C. 1985. Evolution of the ostracods Bradleya and Poseidonamicus in the deep-

sea Cainozoic of the south-west Pacific. Special Papers in Palaeontology 33: 103-116.

WHATLEY, R. C. & Ayress, M. 1988. Pandemic and endemic distribution patterns in Quater-

nary deep-sea Ostracoda. Jn: HANal, T., IkEYA, N. & IsHizaxki, K. eds. Evolutionary

biology of Ostracoda: its fundamentals and applications. Proceedings of the Ninth

International Symposium on Ostracoda, Shizuoka, Japan, 1985: 739-755. Tokyo:

Kodansha/Elsevier.

WHATLEY, R. C. & CoLes, G. P. 1987. The Late Miocene to Quaternary Ostracoda of Leg 94,

Deep Sea Drilling Project. Revista Espanola de Micropaleontologia 19 (1): 33-98.

WHatLey, R. C. & DINGLE, R. V. 1989. First record of an extant, sighted, shallow-water

species of Poseidonamicus (Ostracoda) from the continental margin of south-western

Africa. Annals of the South African Museum 98 (11): 437-457.

Wuat,Ley, R. C. & Masson, D. G. 1979. The ostracod genus Cytheropteron from the Quater-

nary and Recent of Great Britain. Revista Espanola de Micropaleontologia 11 (2):

223-277.

WHATLEY, R. C., HAarRLow, C. J., Downina, S. E. & KESLER, K. J. 1983. Observations on the

origin, evolution, dispersion and ecology of the genera Poseidonamicus Benson and

Bradleya Hornibrook. In: MAppocks, R. L. ed. Applications of Ostracoda. Proceedings

8th International Symposium on Ostracoda, Houston, 1982: 492-509. Houston:

Department of Geosciences, University of Houston.

cyemnntenaatinaenssirmshrstiesepenity jms tain

a 7 : 2

A Pp a = 1 Sa ae _ — = E — a —

6. SYSTEMATIC papers must conform to the International code of zoological nomenclature (particu-

larly Articles 22 and 51).

Names of new taxa, combinations, synonyms, etc., when used for the first time, must be followed

by the appropriate Latin (not English) abbreviation, e.g. gen. nov., sp. nov., comb. nov., syn. nov.,

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An author’s name when cited must follow the name of the taxon without intervening punctuation

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Family Nuculanidae

Nuculana (Lembulus) bicuspidata (Gould, 1845)

Figs 14-15A

Nucula (Leda) bicuspidata Gould, 1845: 37.

Leda plicifera A. Adams, 1856: 50.

Laeda bicuspidata Hanley, 1859: 118, pl. 228 (fig. 73). Sowerby, 1871: pl. 2 (fig. 8a—b).

Nucula largillierti Philippi, 1861: 87.

Leda bicuspidata: Nicklés, 1950: 163, fig. 301; 1955: 110. Barnard, 1964: 234, figs 8-9.

Note punctuation in the above example:

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counter to Recommendation 23 of the Code, to meet the requirements of Biological Abstracts.

R. V. DINGLE, A. R. LORD

I. D. BOOMER

DEEP-WATER QUATERNARY OSTRACODA

FROM THE CONTINENTAL MARGIN OFF

SOUTH-WESTERN AFRICA

(SE ATLANTIC OCEAN)

VOLUME 99 PART 10 DECEMBER 1990 ISSN 0303-2515

Me,

OF THE SOUTH AFRICAN

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BuLLouGH, W. S. 1960. Practical invertebrate anatomy. 2nd ed. London: Macmillan.

FiscHER, P. H. 1948. Données sur la résistance et de la vitalité des mollusques. Journal de conchyliologie 88 (3): 100-140.

FiscHeR, P. H., Duvat, M. & Rarry, A. 1933. Etudes sur les échanges respiratoires des littorines. Archives de zoologie

expérimentale et générale 74 (33): 627-634.

Koun, A. J. 1960a. Ecological notes on Conus (Mollusca: Gastropoda) in the Trincomalee region of Ceylon. Annals and

Magazine of Natural History (13) 2 (17): 309-320.

Koun, A. J. 1960b. Spawning behaviour, egg masses and larval development in Conus from the Indian Ocean. Bulletin of

the Bingham Oceanographic Collection, Yale University 17 (4): 1-51.

THIELE, J. 1910. Mollusca. B. Polyplacophora, Gastropoda marina, Bivalvia. In: SCHULTZE, L. Zoologische und anthro-

pologische Ergebnisse einer Forschungsreise im westlichen und zentralen Stid-Afrika ausgeftihrt in den Jahren

1903-1905 4 (15). Denkschriften der medizinisch-naturwissenschaftlichen Gesellschaft zu Jena 16: 269-270.

(continued inside back cover)

ANNALS OF THE SOUTH AFRICAN MUSEUM

ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM

Volume 99 Band

December 1990 Desember

Part 10 Deel

Kas SZ

WARIO D

S B:9.8:3.9)

A TOOTH-BEARING MAXILLA REFERABLE

TO LYCORHINUS ANGUSTIDENS HAUGHTON,

1924 (DINOSAURIA, ORNITHISCHIA)

Cc. E. GOW

Cape Town Kaapstad

The ANNALS OF THE SOUTH AFRICAN MUSEUM

are issued in parts at irregular intervals as material

becomes available

Obtainable from the South African Museum, P.O. Box 61, Cape Town 8000

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Verkrygbaar van die Suid-Afrikaanse Museum, Posbus 61, Kaapstad 8000

OUT OF PRINT/UIT DRUK

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AGL, tapi), TOD), 8, OGD, 7), 1OGES), 12, S, 7, tp.)

MIGED), 15S), 240), D7, Bi-B), SS), 38,

36(2), 43(1), 45(1), 84(2)

Kopieregnavrae aan die Suid-Afrikaanse Museum

ISBN 0 86813 117 2

Printed in South Africa by In Suid-Afrika gedruk deur

the, Rustica Press, Bty. lids. Die Rustica-pers, Edms., Bpk.,

Court Road, Wynberg, Cape Courtweg, Wynberg, Kaap

C973

A TOOTH-BEARING MAXILLA REFERABLE TO

LYCORHINUS ANGUSTIDENS HAUGHTON, 1924

(DINOSAURIA, ORNITHISCHIA)

C. E. Gow

Bernard Price Institute for Palaeontological Research, University

of the Witwatersrand, Johannesburg, South Africa

(With 7 figures)

[MS accepted 5 December 1989]

ABSTRACT

The taxonomic status of the genera Lycorhinus and Heterodontosaurus, and the various

specimens referred to them, is in an unsatisfactory state, due to incomplete preparation and

description of otherwise good material, a tendency to diagnose specimens rather than species,

and a lack of understanding of the anatomy and functioning of the teeth. A new tooth-bearing

maxilla is described in detail, and both it and the type and only specimen of Lanasaurus scalpri-

dens Gow, 1975, are referred to Lycorhinus angustidens Haughton, 1924, which is also

restudied and reinterpreted here. Although detailed descriptions of the dentition of Hetero-

dontosaurus tucki Crompton & Charig, 1962, have not yet appeared, L. angustidens and

H. tucki are readily distinguishable on postcanine tooth morphology, angle of wear facets, and

pattern of occlusion. Authors have ranked these differently specialized contemporary species as

primitive and advanced; this practice may be questioned.

CONTENTS

PAGE

Mr tnO GC WCEO Re ieee ae eta nee hae etna coe eh ras eon ee te 367

PMS se NWalM xd epee rn ee ON i ac PENA in AR wae te irc Bh ah 368

Lycorhinus angustidens ............... Bk ane ae 371

IBIS CUS SHO Marry ere rs Sree a as ee Ma Nt ary te a a 379

PNCKNOWICAEEMEMUSs arr sees eee ere ames sie ueAnon ies Gla Maen e oa eu § 379

IRCiCREINCCS tears Wr ee ee rn eel ee ee ae 5S 380

INTRODUCTION

In 1984 James Kitching and the author collected a tooth-bearing left maxilla

of an Early Jurassic ornithischian dinosaur. Any new material of these rare and

incompletely known animals is to be welcomed. As the specimen was studied it

became apparent that it is a larger specimen of the species Lanasaurus scalpri-

dens Gow, 1975, and that both are referable to Lycorhinus angustidens

Haughton, 1924. Impressions were accordingly made of the type of L. angusti-

dens, thus enabling a detailed study of the three specimens. The study shows

that Lycorhinus angustidens differs from Heterodontosaurus tucki Crompton &

Charig, 1962. Most described material resides comfortably in one or the other of

367

Ann. S. Afr. Mus. 99 (10), 1990: 367-380, 7 figs.

368 ANNALS OF THE SOUTH AFRICAN MUSEUM

these species, with the exception of Lycorhinus consors Thulborn, 1974. The

much discussed specimen UCL A100 (Thulborn 1970) was probably correctly

identified as L. angustidens; it cannot be grouped with L. consors as Abricto-

saurus Hopson, 1975. The intention of this paper is to refrain as far as possible

from discussing the work of previous authors but rather to concentrate on

presenting new facts and inferences.

The following abbreviations are used to indicate the repositories of the

material studied:

BP — Bernard Price Institute

SAM — South African Museum

UCL — University College, London.

THE NEW MAXILLA

Locality

The farm Bamboeskloof, Lady Grey: 30°45’S 27°12'E, map reference

Floukraal 3027CC.

This locality is less than 15 km from two Heterodontosaurus tucki localities

in the Herschel district (Crompton & Charig 1962; Santa Luca et al. 1976) and

approximately 130 km from the type locality (Mount Fletcher) of Lycorhinus

angustidens Haughton, 1924. Lanasaurus scalpridens Gow, 1975, was found

about 250 km to the north (Golden Gate Highlands National Park). (See

outcrop and locality map in Kitching & Raath 1984, fig. 1.)

Material

The specimen (BP/1/5253) had been exposed to the elements for some time

prior to collection, with the result that the more delicate dorsal and anterior pro-

jections of the maxilla are missing. The cutting edges of the teeth are also

damaged and two crowns are missing.

Preparation

Only a little mechanical preparation was necessary. This was followed by

treatment with thioglycolic acid, but this was discontinued as some damage to

the specimen became evident; this was in any case only cosmetic preparation.

Useful X-ray plates were made from the specimen.

Description (Figs 1, 3-5)

In occlusal view (Fig. 5) three important features are seen: the pit for recep-

tion of the lower canine, the deep cheek region, and the pronounced curvature

of the dental arcade. The dentition is fully developed and well worn, indicating

that this was a mature individual. There are 14 functional teeth and a rudimen-

tary 15th. The teeth invite several descriptive analogies; they are broadest

linguolabially and closely packed like a row of kernels on a maize cob. (The

TOOTH-BEARING MAXILLA OF LYCORHINUS ANGUSTIDENS 369

teeth of Lanasaurus scalpridens are broadest mesiodistally, but this difference

can be attributed to age—compare Fig. 6.) Lingually and labially the crowns

stand out from the roots (as evident in the photographs and indicated by dotted

lines in Fig. 1). This swelling of the crowns is reciprocated by swellings of the

roots at the mesial and distal ‘gum lines’ (for example see tooth 5). The final

analogy is that the teeth have a symmetrical cold-chisel shape with a constant

included angle of about 75° between wear facets and labial crown surfaces. (The

narrower teeth of L. scalpridens have an included angle of 45°. Thus, although

the angle is age dependent, it is worth stressing for comparison with Heterodon-

tosaurus that the new maxilla belonged to a mature individual.) This included

angle is a useful means of comparison as it is not affected by damage to the

cutting edge of the crown and it eliminates subjective reference to vertical and

horizontal axes.

More anterior teeth have taller crowns, whereas mesiodistal crown width

increases towards the back of the tooth row. The crowns have mesial and distal

ridges on their lingual and labial surfaces separated by grooves from the main

body of the crown; the distal ridges and grooves are more pronounced; on the

lingual surface grooves persist for some time as wear proceeds and are thus

important for assessing ages of teeth.

In the following text teeth are referred to by numerals for convenience. Part

of a wear facet is preserved on 2 but this tooth and 3 have lost much of the

crown tips; 5 is lightly worn with part of the posterior groove still present; 6 is

younger than its neighbours, being very little worn; 7 appears to have complex

wear, but the two small basal facets were probably induced by trapped food

rather than direct tooth on tooth contact (this is an old tooth); 8 is also well

worn. Here one begins to see the pattern that persists from this point pos-

teriorly, whereby adjacent wear facets on successive teeth were formed by a

lower tooth in staggered occlusion. This pattern becomes very clear when the

teeth are viewed normal to the wear facets (Fig. 1B—lines on the left in the

figure separate inferred lower teeth). Steps between adjacent teeth in this occlu-

sal view immediately show up young teeth and correlate with those teeth (in

Fig. 1C) that retain traces of a posterior groove (notably 6 and 9; 12 is more

worn). Tooth 9 is lightly worn, 10 is heavily worn with some blurring between

the two main facets, possibly the result of polishing by food but also possibly the

remnant of an earlier facet (as argued for Lycorhinus angustidens—see below).

Tooth 11 has a well-developed pair of wear facets. Tooth 12, though a moder-

ately young tooth (presence of posterior groove), is complicated, as its anterior

facet is actually paired—the result of being opposed by two successive lower

teeth. This tooth also has a large food polish facet. Teeth 13 and 14 are well

worn (retention of the posterior groove on the latter possibly due to delayed

eruption of a suitable antagonist). The rudimentary tooth 15 indicates that this is

a fully elaborated, mature dentition.

Teeth 6, 9 and 12 form a series of increasing age and are clearly younger

than the two teeth that follow each. Replacement thus proceeds from back to

370 ANNALS OF THE SOUTH AFRICAN MUSEUM

A B C

e—

SS 8

———

—=>

L i Clap)

Fig. 1. Lycorhinus angustidens, BP/1/5253, left maxillary dentition. A. Labial view.

B. Viewed normal to the wear facets. C. Lingual view. Note: In A and B hatching denotes

broken areas. In C wear facets are hatched. Lines to the left of B indicated where lower teeth

met each other.

TOOTH-BEARING MAXILLA OF LYCORHINUS ANGUSTIDENS 3

front in the row. This is the same as the pattern described by Gow (1975) for

Lanasaurus scalpridens (Fig. 6) and similar to that by Hopson (1975) for Lyco-

rhinus angusticeps but with a slightly modified interpretation (see below).

This has interesting implications. In the described dentition, teeth within

triplets are arranged in order of increasing age from front to back, but after two

more replacements a stage would be reached when this order would be reversed,

and it was just such a stage that pertained in the maxilla that opposed the type

dentary of Lycorhinus, as demonstrated below. X-rays of the specimen reveal

root canals filled with dense haematite; these show that only a very thin layer of

maxillary bone roofs the deep tooth sockets: the canal fillings terminate at the

alveolar border. In the tooth sequence 6 to 13, root-canal fillings are present for

all except tooth 7—this is probably a quirk of preservation as 7 should be the

last in the series 13—10—7 to be replaced. X-rays of L. scalpridens reveal a full

complement of roots. Although these X-rays show no signs of replacement activ-

ity, this is not a firm indication that replacement had ceased. X-raying is a non-

destructive technique that should be routinely applied and improved.

Lycorhinus angustidens

lanes ZS, 1

The specimen, SAM-—3606, has been well described by Hopson (1975, 1980)

but was re-examined for this study owing to the possibility (now considered

confirmed) that the new maxilla belongs to the same species. In order to take

impressions, the specimen was thoroughly wet and the excess water removed

with compressed air; a fabric-reinforced latex impression was then made, the

first layer being of a very watery consistency. Three impressions were taken and

all are equally good. The impressions were coated with a fine film of sublimating

ammonium chloride, and it is these that were studied and photographed.

The present interpretation differs slightly but significantly from that of

Hopson (1980). The first point, which has not been stressed previously, is the

marked curvature of the postcanine tooth row. When the canine is oriented with

its cutting edges in a sagittal plane, the postcanine row curves back strongly

labiad. (The new maxilla matches this curvature. The best way to see this is to

orientate the photographs of the occlusal view with the first three teeth in the

sagittal plane.) 3

The canine bears serrations on both edges (four per millimetre) as illus-

trated by Hopson (1980, fig. 1). However, most of the distal edge of the tooth is

missing.

Postcanine 1 bears a small mesial cusplet and above it the margin of the

crown is damaged (i.e. there may have been other cusplets). The posterior half

of the labial surface of the crown is damaged and this looks like wear, as the

damaged area has a sharp but smooth enamel edge (the worn area is covered

with matrix grains firmly adhering to the dentine surface).

Postcanine 2 has a worn occlusal edge to the crown; it also has a mesiolabial

wear facet almost certainly formed when the erupted tooth made contact with

—

372 ANNALS OF THE SOUTH AFRICAN MUSEUM

the opposing upper tooth that had earlier been responsible for making the facet

on 1M—the first indication of a staggered pattern of occlusion of upper and

lower cheek teeth, which is argued in detail later. The condition of the labio-

distal surface of 2 is not clear due to adherent matrix, but it does seem confluent

with the anterior facet on 3.

Postcanine 3 has a small distal cusplet high on the crown. There is some

conchoidal fracture of the dentine at the tip of the crown but this does not mask

two distinct wear facets dipping slightly away from each other. Tooth 4 is very

similar though more worn and better preserved. Hopson’s (1980) interpretation

of tooth 5, 1.e. one major wear facet and a small polished area, is accepted.

Hopson interpreted tooth 6 in the same way but the larger lower facet is in fact

in perfect contiguity with the anterior facet on tooth 7, thus demonstrating the

presence of an upper tooth in overlapping occlusion with 6 and 7.

Postcanine 7 is an old tooth; its posterior wear facet bears a wide, deep,

smoothly rounded groove. This groove must have been formed by a step

between adjacent edges of occluding upper teeth at different stages of wear. A

small facet is present on the mesial edge of 8. By tilting the specimen it is poss-

ible to see that this facet lies on the same arc as the distal facet on 7—these

facets are thus attributable to the same upper tooth. The author is not convinced

that there is sufficient evidence for the same situation pertaining between 8

and 9, but agrees with Hopson (1980) that it seems likely. The large wear facets

on 8 and 9 have deliberately been left unhatched in Figure 2 because these teeth

| 1cm |

Fig. 2. Lycorhinus angustidens, SAM-—3606. Impression of left dentary teeth. Hatching indi-

cates wear facets but has been deliberately omitted from teeth 8, 9 and 10. Teeth 8 and 9 bear

striations, 9 and 10 have heels shown by shading, and 10 bears a raised ridge with the same

orientation as the striations on 8 and 9. Wear facet on canine is on the lingual surface of the

tooth.

TOOTH-BEARING MAXILLA OF LYCORHINUS ANGUSTIDENS 373

bear patches of striations indicating direction of bite. These striations are helpful

to understanding the bite, which is seen to have a posteriad component. It is

important to note that the striations have the same orientation as the ridge on

tooth 10 discussed below. That such striations are rare suggests a degree of

imprecision in the bite such that occluding surfaces are continuously roughly pol-

ished. Teeth 9 and 10 have heels worn into the base of their facets. The present

interpretation of 10 and 11 differs from Hopson’s but is made with the benefit of

the hindsight afforded by the new maxilla. Tooth 10 has a raised ridge between

facets, such as would result if the edges of occluding uppers did not quite meet.

The preserved portion of the 11th tooth was clearly part of a perfectly

normal full-sized tooth; it is faceted and is raised labiad of 10, and it was thus

opposed by the successor to the tooth responsible for the posterior facet on 10.

It is suggested that the differences in wear facet orientation that Hopson (1980)

recorded (supposedly increasingly horizontal with age) are illusory, as witness

the continuity of facets on 7 with those of its neighbours. Indeed tooth 4 seem-

ingly has the most nearly horizontal wear facets, but is less worn than tooth 5,

which apparently has more oblique facets. This specimen represents a mature

animal of a species characterized by very oblique wear facets. Three more teeth

could have been present in the living dentary (see Fig. 3).

This dentition contains ample evidence of a staggered occlusal arrangement

between upper and lower teeth. In Figure 2 vertical lines above teeth indicate

where upper teeth would meet each other. Some of the most interesting and

instructive lower teeth are those that at first sight apparently do not conform to

this staggered pattern. The best place to begin is with tooth 6: here it is seen

that a second wear facet has started to encroach on a previously existing single

facet—the new facet would continue to enlarge and migrate forward as indi-

cated by the arrow. One can postulate that exactly the same thing would happen

in time to tooth 5. Teeth 8 and 9 differ in that they have very well-developed

1cm |

Fig. 3. Lycorhinus angustidens. Composite drawing of BP/1/5253 and SAM—3606. The speci-

mens fit rather well and give an indication of the degree of incompleteness of the dentary tooth

row. For reasons explained in the text, wear facets cannot be directly compared.

374 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 4. Lycorhinus angustidens, BP/1/5253. Above. Labial view. Below. Lingual view.

Scale bar = 1 cm.

TOOTH-BEARING MAXILLA OF LYCORHINUS ANGUSTIDENS 375

Fig. 5. Lycorhinus angustidens, BP/1/5253. Above. Occlusal view. Below. View normal to

wear facets. Scale bar = 1 cm.

376 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 6. Lycorhinus angustidens (Lanasaurus scalpridens), BP/1/4244. Above. Labial view.

Below. Lingual view. Scale bar = 1 cm.

TOOTH-BEARING MAXILLA OF LYCORHINUS ANGUSTIDENS 37

Fig. 7. Lycorhinus angustidens, SAM-3606. Original above. Positive impression below.

Scale bar = 1 cm.

378 ANNALS OF THE SOUTH AFRICAN MUSEUM

single facets, and incipient facets on their anterior edges. These latter facets

would migrate posteriad in time until these teeth reached the condition seen in

tooth 10, which has two distinct but very well-worn facets. After this the tooth

would be shed. The difference in direction of facet migration has little to do with

position in the tooth row, but seems rather to be related to the extent of wear of

the teeth. From the above, the following sequence can be inferred.

(a) A single wear facet forms fairly symmetrically over the labial surface of the

crown of a dentary tooth (as previously noted by Hopson such a facet is

concave—the opposing upper teeth would be well worn and would present a

convex surface). This is not apparent from Figure 1B and perceptions of facet

curves change as the specimen is rotated about its longitudinal axis. At its best

development each of a pair of facets on adjacent teeth is concave, hence a con-

vexity is formed where they meet. This is seen in the occlusal stereophotograph

(Fig. 5) between teeth 7 and 8, and 10 and 11.

(b) A second facet forms posteriorly when a new upper tooth comes into occlu-

sion. This facet migrates forward and eventually dominates the crown as the

tooth anterior to it is shed (this facet extends further down the crown—quite

obviously this must be so).

forms, this time on the anterior edge of the tooth, and this migrates backwards

to result in the condition seen on tooth 10. At this stage the tooth would be

replaced.

This interpretation highlights, and is itself supported by, the pattern of trip-

lets in the Lycorhinus jaw. Arranged from youngest to oldest, these are 5, 6

and 7, and 8, 9 and 10. This interpretation differs from that of Hopson (1975,

1980), who proposed the following triplets: 4, 5 and 6, and 7, 8 and 9. Turning

to the anterior teeth, it appears that 4 is more worn than 3, but both have two

facets, whereas 2 has a single (first wear stage) facet; thus these teeth conform to

the pattern of triplets proposed here.

We now have the interesting situation where both maxilla and dentary bear

triplets of teeth that consistently range in age from front to back. For the lower

jaw one can demonstrate that each triplet would require to be opposed by a

battery of teeth in which the reverse situation pertained. To do this we can look

at the hypothetical maxillary (M) triplet 6, 7 and 8 that occluded with dentary

(D) teeth 6, 7, 8 and 9 at the time the bearer of the Lycorhinus type died.

Tooth M6 was well ground in, M7 had only recently made contact with D8,

whereas M8 may just have made contact with D9. We can also look at D9, 10

and 11: the oldest tooth in the next maxillary series should be M9—that fits;

M10 should be mature but not as old as M9 and again this is borne out by the

wear facet on D11. All this makes eminently good sense, as, if occluding teeth

were to erupt together, the amount of attrition would presumably be greater and

the teeth would wear faster.

The pattern of wear on the teeth in the new maxilla has been frozen at a

different stage in the cycle, which makes it look different and more difficult to

TOOTH-BEARING MAXILLA OF LYCORHINUS ANGUSTIDENS 379

interpret. The teeth appear more regularly bifaceted. That the same sequence as

demonstrated for the dentary still applies, is shown by the following teeth: 9 has

first and second wear stage facets, 12 is unusual in that first, second and third

stage facets are present, whereas 7 has a partially obliterated second wear stage

facet and a well-developed third wear stage facet. (Polish facets on 7 and 12 are

ignored.)

DISCUSSION

As a result of the foregoing description and analysis, tooth morphology,

function and replacement are well understood, and the variation inherent in the

system must lead to the conclusion that there is a high probability that Lana-

saurus scalpridens and the new maxilla BP/1/5253 belong to the species

Lycorhinus angustidens. The much discussed but poorly known specimen

UCL A100 (Thulborn 1970) may also belong to this species.

The very similar species Heterodontosaurus tucki is known from a complete

skeleton (Santa Luca et al. 1976), a complete skull (Crompton & Charig 1962),

and possibly an undescribed jaw fragment (Charig & Crompton 1974).

Lycorhinus consors Thulborn, 1974, is an enigma, apparently possessing the

teeth and wear pattern of Lycorhinus and the occlusal pattern of Heterodonto-

saurus.

Heterodontosaurus has more strongly ridged teeth with more transverse

wear facets, and occlusion is nearly if not entirely opposite. Hopson (1980)

demonstrated the same pattern of replacing triplets for Heterodontosaurus, as 1s

now well documented for Lycorhinus.

Hopson (1980) remarked that the Lanasaurus maxilla was larger than the

maxilla of Heterodontosaurus. The new maxilla is still larger, and fits the Lyco-

rhinus dentary rather well; thus Lycorhinus could well have been a larger animal

than Heterodontosaurus.

On the basis of the foregoing discussion, the maxilla BP/1/5253 is referred

to Lycorhinus angustidens Haughton, 1924, and a revised synonymy for this

species is presented below.

Lycorhinus angustidens Haughton, 1924

Lycorhinus angustidens Haughton, 1924: 343-344, fig. 8. Thulborn, 1970: 236-241, figs 1-5.

Abrictosaurus consors (Thulborn, 1974) Hopson, 1975: 304 (part. —-UCL A100 only).

Lanasaurus scalpridens Gow, 1975: 336-339, text-figs 1-2, pl. 1.

ACKNOWLEDGEMENTS

I wish to thank the Director of the South African Museum, Dr M. A.

Cluver, for the loan of the Lycorhinus type, Dr J. van den Heever who packed

it so beautifully and Mrs Ann Lawton who kindly added the package to her

family holiday luggage.

380 ANNALS OF THE SOUTH AFRICAN MUSEUM

REFERENCES

Cuaric, A. J. & Crompton, A. W. 1974. The alleged synonomy of Lycorhinus and Hetero-

dontosaurus. Annals of the South African Museum 64: 167-189.

Crompton, A. W. & Cuaric, A. J. 1962. A new ornithischian from the Upper Triassic of

South Africa. Nature, London 196 (4859): 1074-1077.

Gow, C. E. 1975. A new heterodontosaurid from the Redbeds of South Africa showing clear

evidence of tooth replacement. Zoological Journal of the Linnean Society of London 57

(4): 335-339.

Haucuton, S. H. 1924. The fauna and stratigraphy of the Stormberg Series. Annals of the

South African Museum 12 (8): 323-497.

Hopson, J. A. 1975. On the generic separation of the ornithischian dinosaurs Lycorhinus and

Heterodontosaurus from the Stormberg Series (Upper Triassic) of South Africa. South

African Journal of Science 71 (10): 302-305.

Hopson, J. A. 1980. Tooth function and replacement in early Mesozoic ornithischian dino-

saurs: implications for aestivation. Lethaia 13 (1): 93-105.

KITCHING, J. W. & RaatH, M. A. 1984. Fossils from the Elliot and Clarens formations (Karoo

sequence) of the Northeastern Cape, Orange Free State and Lesotho, and a suggested

biozonation based on tetrapods. Palaeontologia africana 25: 111-125.

SANTA Luca, A. P., Crompton, A. W. & Cuaric, A. J. 1976. A complete skeleton of the Late

Triassic ornithischian Heterodontosaurus tucki. Nature, London 264 (5584): 324-328.

THULBORN, R. A. 1970. The systematic position of the Triassic ornithischian dinosaur Lyco-

rhinus angustidens. Zoological Journal of the Linnean Society of London 49 (3): 235-245.

THULBORN, R. A. 1974. A new heterodontosaurid dinosaur (Reptilia: Ornithischia) from the

Upper Triassic Redbeds of Lesotho. Zoological Journal of the Linnean Society of London

55 (2): 151-175.

6. SYSTEMATIC papers must conform to the International code of zoological nomenclature (particu-

larly Articles 22 and 51).

Names of new taxa, combinations, synonyms, etc., when used for the first time, must be followed

by the appropriate Latin (not English) abbreviation, e.g. gen. nov., sp. nov., comb. nov., syn. nov.,

etc.

An author’s name when cited must follow the name of the taxon without intervening punctuation

and not be abbreviated; if the year is added, a comma must separate author’s name and year. The

author’s name (and date, if cited) must be placed in parentheses if a species or subspecies is trans-

ferred from its original genus. The name of a subsequent user of a scientific name must be separated

from the scientific name by a colon.

Synonymy arrangement should be according to chronology of names, i.e. all published scientific

names by which the species previously has been designated are listed in chronological order, with all

references to that name following in chronological order, e.g.:

Family Nuculanidae

Nuculana (Lembulus) bicuspidata (Gould, 1845)

Figs 14-15A

Nucula (Leda) bicuspidata Gould, 1845: 37.

Leda plicifera A. Adams, 1856: 50.

Laeda bicuspidata Hanley, 1859: 118, pl. 228 (fig. 73). Sowerby, 1871: pl. 2 (fig. 8a—b).

Nucula largillierti Philippi, 1861: 87.

Leda bicuspidata: Nicklés, 1950: 163, fig. 301; 1955: 110. Barnard, 1964: 234, figs 8—9.

Note punctuation in the above example:

comma separates author’s name and year

semicolon separates more than one reference by the same author

full stop separates references by different authors

figures of plates are enclosed in parentheses to distinguish them from text-figures

dash, not comma, separates consecutive numbers.

Synonymy arrangement according to chronology of bibliographic references, whereby the year is

placed in front of each entry, and the synonym repeated in full for each entry, is not acceptable.

In describing new species, one specimen must be designated as the holotype; other specimens

mentioned in the original description are to be designated paratypes; additional material not regarded

as paratypes should be listed separately. The complete data (registration number, depository, descrip-

tion of specimen, locality, collector, date) of the holotype and paratypes must be recorded, e.g.:

Holotype

SAM-—A13535 in the South African Museum, Cape Town. Adult female from mid-tide region, King’s Beach, Port Eliza-

beth (33°51’S 25°39’E), collected by A. Smith, 15 January 1973.

Note standard form of writing South African Museum registration numbers and date.

7; SPECIAL HOUSE RULES

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e.g. “. . . the Figure depicting C. namacolus ...’: *. . . in C. namacolus (Fig. 10)... .’

(b) The prefixes of prefixed surnames in all languages, when used in the text, if not preceded by

initials or full names

e.g. Du Toit but A.L. du Toit; Von Huene but F. von Huene

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Punctuation should be loose, omitting all not strictly necessary

Reference to the author should preferably be expressed in the third person

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Specific name must not stand alone, but be preceded by the generic name or its abbreviation to initial

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Name of new genus or species is not to be included in the title; it should be included in the abstract,

counter to Recommendation 23 of the Code, to meet the requirements of Biological Abstracts.

C. E. GOW

A TOOTH-BEARING MAXILLA

REFERABLE TO

LYCORHINUS ANGUSTIDENS

HAUGHTON, 1924

(DINOSAURIA, ORNITHISCHIA)

7x VOLUME 99 PART 11 FEBRUARY 1991 ISSN 0303-2515

‘

“OF THE SOUTH AFRICAN -

MUSEUM

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paper, using the Harvard System (ibid., idem, loc. cit., op. cit. are not acceptable):

(a) Author’s name and year of publication given in text, e.g.:

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Examples (note capitalization and punctuation)

BuLLouGH, W. S. 1960. Practical invertebrate anatomy. 2nd ed. London: Macmillan.

FiscHER, P. H. 1948. Données sur la résistance et de la vitalité des mollusques. Journal de conchyliologie 88 (3): 100-140.

FiscHer, P. H., Duvat, M. & Rarry, A. 1933. Etudes sur les échanges respiratoires des littorines. Archives de zoologie

expérimentale et générale 74 (33): 627-634.

Koun, A. J. 1960a. Ecological notes on Conus (Mollusca: Gastropoda) in the Trincomalee region of Ceylon. Annals and

Magazine of Natural History (13) 2 (17): 309-320.

Koun, A. J. 1960b. Spawning behaviour, egg masses and larval development in Conus from the Indian Ocean. Bulletin of

the Bingham Oceanographic Collection, Yale University 17 (4): 1-51.

THIELE, J. 1910. Mollusca. B. Polyplacophora, Gastropoda marina, Bivalvia. In: ScHULTZE, L. Zoologische und anthro-

pologische Ergebnisse einer Forschungsreise im westlichen und zentralen Siid-Afrika ausgeftihrt in den Jahren

1903-1905 4 (15). Denkschriften der medizinisch-naturwissenschaftlichen Gesellschaft zu Jena 16: 269-270.

(continued inside back cover)

ANNALS OF THE SOUTH AFRICAN MUSEUM

ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM

Volume 99 Band

February 1991 Februarie

Part 11 Deel

NSA |

S BBdBe

ww! {

Q. &

Svouig novi NS

A REVISED DESCRIPTION OF THE SKULL OF

MOSCHORHINUS

(THERAPSIDA, THEROCEPHALIA)

J. F. DURAND

Cape Town Kaapstad

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C970

A REVISED DESCRIPTION OF THE SKULL OF MOSCHORHINUS

(THERAPSIDA, THEROCEPHALIA)

J. F. DURAND

Bernard Price Institute for Palaeontology, University of the Witwatersrand*

(With 17 figures)

[Paper presented at the Palaeontological Society of southern Africa Symposium, Cape Town,

September 1986 |

ABSTRACT

Certain aspects of the external morphology of the Moschorhinus skull have been misinter-

preted or overlooked in previous studies. In this paper the external morphology of the posterior

half of the Moschorhinus skull is discussed in detail. The bony elements forming the braincase

and the morphology of the foramina, fossae and grooves visible on the exterior surface of the

braincase are described, and their possible functions are discussed. Certain misconceptions con-

cerning the morphology of the prootic, opisthotic, quadrate, pterygoid, squamosal and

epipterygoid are corrected. In the light of these findings the taxonomic position of Moscho-

rhinus relative to other therocephalians is discussed.

CONTENTS

PAGE

MMO CICLO Ieee ere aer ent ees a erent e vA ah ONE 381

WiatenralvandsniGthiod Savy ete sesh erceerect cs eee SNe nee irRlemsl lance aes 382

DCS CHILO Meer ar crate et wiftiaceate cette any Siauccger a uate Alera 383

DISCUSSION Seer ee eee ey ieee ee eo en Mme ere he ee ek Eo 406

PXCKMOWIEASEMEN(S arene Gein oe mor caheern ae var etna nar aie renee Bak 410

IRRENETRSINCES Oe ie 1 neh Nears ae ane AE MONAT Sn a TU peer a ge ee 411

JNO OFREREUBIOIINS: aaron cscs veneer aCe ean OURO sae ORR MIR) atten ei een 413

INTRODUCTION

The interrelationships of the Therocephalia and their relationship with the

Cynodontia are not adequately known. Certain authors, such as Broom (1938),

Brink (1951), Hopson & Crompton (1969), and Kemp (1982), are of the opinion

that the cynodonts had a therocephalian ancestor, whereas others such as

Romer (1969) and Kermack & Kermack (1984) have argued that the cynodonts

arose independently of the Therocephalia, from a more primitive ancestor. Most

of the former authors accepted scaloposaur ancestry for the cynodonts, whereas

Kemp (1972, 1982) argued that the cynodont ancestor was closely related to the

whaitsiids.

To unravel therapsid phylogeny it is essential to know more about thero-

cephalian morphology. The present study attempts to broaden our knowledge of

* Present address: Geological Survey, Private Bag X112, Pretoria.

381

Ann. S. Afr. Mus. 99 (11), 1991; 381-413, 17 figs.

382 ANNALS OF THE SOUTH AFRICAN MUSEUM

Moschorhinus kitchingi, which is an interesting therocephalian with a mixture of

primitive and advanced characteristics.

Moschorhinus seems to be more advanced than the pristerognathids and

scaloposaurids, even though it has certain features in common with the gor-

gonopsians. Moschorhinus shares more characteristics with the whaitsiids than

with any other therocephalian group. Moschorhinus is also more primitive than

the whaitsiids but does not seem to be ancestral to them. The taxonomic pos-

ition of Moschorhinus will be discussed in detail later.

The skull of Moschorhinus has been described by Broom (1920), Boonstra

(1934), Brink (1959), and Mendrez (1974a). The elements forming the anterior

half of the skull are well known from these descriptions. However, due to the

poorly preserved braincase in most Moschorhinus specimens, or insufficient

preparation thereof, certain misconceptions arose concerning the relations of the

elements constituting the posterior half of the skull.

Two Moschorhinus skulls were selected for this study. Although these skulls

are somewhat damaged and distorted, the posterior parts of the skulls are in

such a condition that, with careful preparation it was possible to discover a

wealth of information that adds to our knowledge of the Moschorhinus skull. In

this paper the elements constituting the posterior half of the skull and the inter-

relationships between these elements are described, and the possible courses of

certain blood-vessels and nerves are discussed.

MATERIAL AND METHODS

Two previously undescribed specimens were selected for this study:

Moschorhinus kitchingi (Broom) BP/1/2788 and BP/1/4636. BP/1/2788 was found

by J. W. Kitching in Stoffelton, Afdeel Native Trust (now part of KwaZulu),

near Bulwer, Natal, in the Daptocephalus zone (Kitching 1977) (Dicynodon

lacerticeps—Whaitsia Assemblage-zone—S.A.C.S. 1980). BP/1/4636 was found

by J. W. Kitching on the farm Fairydale in the Bethulie district, Orange Free

State in the Lystrosaurus zone (Kitching 1977) (Lystrosaurus—Thrinaxodon

Assemblage-zone—S.A.C.S. 1980).

Moschorhinus kitchingi, BP/1/2788 (Figs 1-4)

Most of the matrix surrounding this skull had been removed with a hammer

and chisel prior to this study. The matrix within the temporal cavities had not

been removed. This distorted specimen is 21,5 cm long. The major parts of the

skull roof and occiput are missing and the jugal and postorbital arches are

damaged. Teeth are present in the damaged and distorted mandible. Aspects of

this specimen’s teeth and mandible were used in the reconstruction of the lateral

view of the skull (Fig. 14).

Moschorhinus kitchingi, BP/1/4636 (Figs 5-11)

The whole skull was prepared for this study by means of an air-hammer and

engraving tool. This distorted skull is 25 cm long. Parts of its jugal and post-

REVISED DESCRIPTION OF MOSCHORHINUS 383

orbital arches are missing and the occiput is damaged. Although this skull is

severely damaged, it yielded vital information. The descriptions and reconstruc-

tion of the posterior part of the skull and the dental formula are those of this

specimen (Figs 12-17).

DESCRIPTION

The posterior half of the Moschorhinus skull consists of the following

endochondral elements: the epipterygoid, prootic, opisthotic, quadrate, supra-

occipital, exoccipital and basioccipital, and the following dermal elements: the

squamosal, quadratojugal, jugal, interparietal, parietal, postorbital, tabular and

pterygoid. The parasphenoid and basisphenoid are of endochondral and dermal

origin.

The lateral wall of the braincase can be seen within the jugal arch (Fig. 16).

The large parietal forms the sharp-crested roof of the braincase and the dorsal

border of the temporal fossa. The posterior wall of the temporal fossa is largely

formed by the squamosal. The medial wall of the temporal fossa is formed by

the epipterygoid, the prootic, the ventrolateral part of the pterygoid, the lateral

part of the opisthotic, and anterior parts of the supraoccipital and interparietal.

Several features relating to blood-vessels and nerves can be seen within the

temporal fossa.

The posterior surfaces of the parietal, interparietal and supraoccipital form

the medial surface of the occiput, dorsal to the foramen magnum (Fig. 15).

These elements are flanked by the tabulars, which cover part of the squamosal

posteriorly. The lateral part of the occiput is formed by the posterior parts of the

squamosal and the opisthotic. The foramen magnum is flanked by the exoccipi-

tals. The ventromedial border of the occiput is marked by the basioccipital. Two

of the most salient features of the occiput are the large post-temporal fenestra

and the paroccipital fossa.

EPIPTERYGOID (Figs 12-14, 16)

In lateral view (Figs 14, 16), the flattened, blade-like epipterygoid can be

seen. It contacts the parietal, supraoccipital and prootic dorsally and the ptery-

goid, prootic and squamosal ventrally. The upper part of the processus

ascendens (dorsal lamina—Mendrez 1972, 1974a, 1974b) expands anteriorly to

form an anterodorsal process and posteriorly to form a posterodorsal process.

The basal part of the epipterygoid expands anteriorly to form an anteroventral

process and posteriorly to form a posteroventral process (Mendrez 1972, 1974a,

1974b). A small posterior apophysis is present on the posterior edge of the pro-

cessus ascendens, which probably made contact with the lateral part of the base

of the anterodorsal process of the prootic (unfortunately damaged in all Mos-

chorhinus specimens examined). The ventromedial part of the posterodorsal pro-

cess of the epipterygoid contacts the anterolateral part of the anterodorsal process

of the prootic just above the contact of the posterior apophysis with the prootic,

384 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 1. Moschorhinus kitchingi. BP/1/2788. Dorsal view.

Fig. 2. Moschorhinus kitchingi. BP/1/2788. Ventral view.

REVISED DESCRIPTION OF MOSCHORHINUS 385

Fig. 3. Moschorhinus kitchingi. BP/1/2788. Lateral view.

Fig. 4. Moschorhinus kitchingi. BP/1/2788. Oblique anterior view.

386 ANNALS OF THE SOUTH AFRICAN MUSEUM

thus forming a circular foramen—the posterior foramen of the epipterygoid

(‘foramen veineux’—Mendrez 1974a) (see Fig. 16). There is a shallow funnel-

like indentation surrounding the foramen on the lateral surface of the epiptery-

goid. A low ridge runs diagonally across the lateral surface of the epipterygoid

from the tip of the posterodorsal process, passes anterior to the foramen, and

terminates in the middle of the ventral part of the epipterygoid as a small tuber-

osity. This posterior foramen of the epipterygoid should not be confused with

the dorsal venous foramen (see discussion). The dorsal border of the epiptery-

goid fits in snugly under the parietal. The central part of the dorsal border of the

epipterygoid is overlapped laterally by the ventrolateral descending flange of the

parietal. The tip of the posterodorsal process curves slightly downwards, away

from the parietal, exposing the interparietal upon which the dorsal part of the

posterodorsal process lies.

The anteroventral process of the epipterygoid is quite small in relation to

the posteroventral process. It originates anteroventrally from the base of the

processus ascendens. The anteroventral process terminates anteriorly to the

dorsolateral ridge of the pterygoid and is in confluence with the posterior corner

of this ridge. The term anteroventral process of the epipterygoid is preferred to

the ‘pterygoid process of the epipterygoid’ (Crompton 1955) since the whole of

the ventral border of the epipterygoid contacts the pterygoid. The foot of the

epipterygoid covers the dorsal surface of the anterolateral third of the quadrate

ramus of the pterygoid (see Figs 12, 16).

The posteroventral process of the epipterygoid originates at the base of the

processus ascendens from where it flares out posterolaterally as an elongated,

horizontal fan, overlying the middle third of the quadrate ramus of the ptery-

goid. These two processes are confluent laterally and posteriorly but not

medially and anteriorly. The posteroventral process is slightly raised medially

along its whole length, producing a medially facing groove that originates under

the vertically inclined anterior part of the posteroventral process. The groove

tapers off as it approaches the posterior border of the posteroventral process.

The term posteroventral process of the epipterygoid is preferred to the

‘quadrate process of the epipterygoid’ (Crompton 1955), since it is doubtful

whether the epipterygoid actually did contact the quadrate in Moschorhinus.

The posterior part of the posteroventral process of the epipterygoid is fan-

shaped. The lateral half of the posterior border stretches across the dorsal

surface of the quadrate ramus of the pterygoid. The posterior border contacts

the anterior border of the anteroventral process of the squamosal medially, the

contact being visible in dorsal and ventral views. This region of the epipterygoid

forms part of the anterolateral corner of the pterygo-paroccipital foramen (see

Jers 1172, 113),. ING):

In lateral view (Fig. 16), the ventral suture of the epipterygoid runs in the

middle of the lateral side of the structure formed with the quadrate ramus of

the pterygoid. The suture dips anteriorly and then curves upwards delimiting the

border of the anteroventral process. Posteriorly the suture runs diagonally

REVISED DESCRIPTION OF MOSCHORHINUS 387

Fig. 5. Moschorhinus kitchingi. BP/1/4636. Dorsal view.

Fig. 6. Moschorhinus kitchingi. BP/1/4636. Ventral view.

388 ANNALS OF THE SOUTH AFRICAN MUSEUM

upwards in a straight line delimiting the ventral border of the posteroventral

process laterally on the dorsal side of the quadrate ramus of the pterygoid.

The processus ascendens of the epipterygoid juts upwards and slightly

inwards. The middle part of the processus ascendens is relatively constricted in

comparison with the dorsal and ventral parts, giving the epipterygoid an hour-

glass shape in lateral view. The ventral part of the epipterygoid is directed out-

wards posteriorly and inwards anteriorly. This closely reflects the orientation of

the quadrate ramus of the pterygoid, whereas the dorsal part of the epipterygoid

is more parasagittally inclined.

A very distinct and large cavum epiptericum is present, bordered medially

by the anteroventral process of the prootic and laterally by the epipterygoid.

Certain nerves and veins traverse the cavum epiptericum (see discussion).

Fig. 7. Moschorhinus kitchingi. BP/1/4636. Left lateral view.

Fig. 8. Moschorhinus kitchingi. BP/1/4636. Right lateral view.

REVISED DESCRIPTION OF MOSCHORHINUS 389

Fig. 9. Moschorhinus kitchingi. BP/1/4636. Occipital view.

PROOTIC (Figs 12-17)

The prootic and opisthotic are two separate elements. The sutures dividing

these bones will be discussed later.

The prootic is a complex bone with five major processes. The terminology

used by Mendrez (1972) to describe these processes will be followed here. The

prootic meets the basisphenoid ventrally, the squamosal and opisthotic postero-

laterally, the epipterygoid anterolaterally, and the supraoccipital dorsally.

In lateral view (Fig. 16), two distinct ridges can be seen running diagonally

across the prootic, more or less parallel to each other. The ridge running from

the central process to the anterodorsal process is here called the central ridge of

the prootic (the ‘delicate rising crest’ of Mendrez 1972: 205). The ridge running

from the lip of the fenestra ovalis to the anteroventral process of the prootic, is

here called the ventral ridge of the prootic (the ‘sharp crest—Mendrez 1972:

203; the ‘strong crest’ —Mendrez 1972: 205; 1974b: 76).

In lateral view it can be seen that the prootic has two distinct anterior pro-

cesses directed diagonally anterodorsally, viz: the anterodorsal process above

and anteroventral process below. These two processes are separated by the

incisura prootica. Olson (1944), Crompton (1955), Mendrez (1972) and others

used these terms to describe the anterior part of the prootic.

The anterior part of the anterodorsal process makes contact with the medial

surface of the epipterygoid, whereas the anteroventral process passes medially

to the epipterygoid, forming a large vacuity between it and the epipterygoid—

390 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 10. Moschorhinus kitchingi. BP/1/4636. Detail of left temporal region.

Fig. 11. Moschorhinus kitchingi. BP/1/4636. Dorsolateral view of left temporal region.

REVISED DESCRIPTION OF MOSCHORHINUS 391

the cavum epiptericum, which will be discussed later. The anterodorsal process

runs more or less parallel to the sagittal plane, whereas the anteroventral

process points inwards.

The anterodorsal process of the prootic (processus anterior superior—

Siebenrock 1893; posterior prootic process—Boonstra 1934) is a flattened,

broad, projection that originates more or less in the middle of the prootic. Its

dorsal border is continuous with the dorsal border of the rest of the prootic, and

its ventral border is a continuation of the central ridge of the prootic. The antero-

dorsal process is rather broad posteriorly but tapers anteriorly, the thinnest part

being its anterior edge, which contacts the posteromedial edge of the epi-

pterygoid laterally. This region is damaged in the specimen described by

Mendrez (1974a). The anteroventral edge of the anterodorsal process forms the

posterior border of the posterior foramen of the epipterygoid. There is a slight

lateral protrusion on the posterior part of the ventral border of the anterodorsal

process, causing a ventrolaterally directed protuberance in the central ridge of

the prootic. This is probably where the prootic made contact with the posterior

apophysis of the epipterygoid, because of its inclination towards, and proximity

to, the apophysis.

Bordering the anterodorsal process of the prootic dorsally and meeting the

anterodorsal process of the epipterygoid is the flat, finger-like anterolateral

process of the supraoccipital. The suture between the supraoccipital and prootic

is not continuous. Posterior to the ventral edge of the posterodorsal process of

the epipterygoid, a small triangular gap is formed between the supraoccipital

and prootic. This is the dorsal venous foramen commonly found in many

therapsids (see discussion).

The plane of the anterodorsal process is diagonally inclined in cross-section.

The ventral border flares out laterally, whereas the dorsal border is medially

inclined, reflecting the orientation of the epipterygoid.

The anteroventral process of the prootic (processus anterior inferior—

Siebenrock 1893; anterior prootic process—Boonstra 1934) originates below the

contact between the posterior apophysis of the epipterygoid and the antero-

dorsal process. This process is the ossified pila antotica (pleurosphenoid)

(De Beer 1937; Olson 1944; Save-Sdderbergh 1947; Crompton 1955). The

dorsal border of the anteroventral process curves upwards in a crescent shape.

The anteroventral process is vertically inclined in cross-section and curves

inwards anteriorly. The anteroventral process is traversed anteriorly by a

horizontal groove. Above this shallow indentation, a low ridge runs from the

posterior border of the incisura prootica anteriorly. This low ridge flares out

anteriorly, forming two small, anteriorly jutting projections.

The incisura prootica is wide and deep. It is bordered ventrally by the

concave dorsal border of the anteroventral process and dorsally by the straight

ventral border of the anterodorsal process.

The foramen for the facial nerve (VII) is situated between the central and

ventral ridges of the prootic. This foramen is nearer the former ridge and on the

392 ANNALS OF THE SOUTH AFRICAN MUSEUM

dpSq

ipSq

O 3cm loe

Fig. 12. Moschorhinus kitchingi. Dorsal view.

same level as the ventral border of the anteroventral process of the prootic

anterior to it, and the central process of the prootic posterior to it.

There is a small ventral notch between the ventral border of the antero-

ventral process and the braincase floor. Its posterior border is formed by the

anterior border of the basal region of the prootic. The ventral border is formed by

the basisphenoid. This is the same as the notch described by Crompton (1955) for

the Scalaposauridae, though here it is more open anteriorly.

The prootic has three prominent lateral processes of approximately the

same length. The central process of the prootic (lateral process of the prootic—

REVISED DESCRIPTION OF MOSCHORHINUS 393

mpSq

ptpf

Fig. 13. Moschorhinus kitchingi. Ventral view.

Kemp 1972) can be seen in lateral (Fig. 16), dorsal, ventral and occipital views.

It juts out laterally and slightly posteroventrally towards the squamosal. Its

anterolateral corner contacts the posteromedial corner of the posteroventral

process of the epipterygoid. The medial part of the anteroventral process of the

squamosal (prootic process of the squamosal—Mendrez 1974b) contacts this

central process in a complex manner: the distal part of the central process forms

two flanges, one anterodorsally, the other posteroventrally, between which the

thin medial blade of the anteroventral process of the squamosal is wedged.

394 ANNALS OF THE SOUTH AFRICAN MUSEUM

Soc

Fig. 14. Moschorhinus kitchingi. Lateral view.

These two elements form an anterodorsally curving bar that forms the anterior

border of the pterygo-paroccipital foramen. The dorsal crest-like border of this

bar is a continuation of the central ridge of the prootic. The anteroventral

border of this bar forms a sharp concave crest running from the dorsal lip of the

fenestra ovalis medially to the posteromedial corner of the posteroventral

process of the epipterygoid laterally. The distal part of the céntral process is

spindle-shaped in cross-section. The base of the central process, however, is

triangular in cross-section, because of a short, sharp crest that forms the

posteromedial corner of the process. This crest originates on the posteromedial

part of the central process, curves posteromedially and terminates on the

anterior surface of the posteroventral process of the prootic.

Behind the central process of the prootic, a more posteriorly inclined,

flattened process, the posteroventral process of the prootic, originates. This

process can be seen in occipital view. It contacts the opisthotic ventrolaterally.

This unified structure forms the posterior wall of the pterygo-paroccipital

foramen, the ventral border of the post-temporal fenestra and the anterior wall

of the paroccipital fossa. The posteroventral process forms only the dorsomedial

quarter of the posterior wall of the pterygo-paroccipital foramen and the medial

half of the ventral border of the post-temporal fenestra.

A third process, the posterodorsal process of the prootic, contacts the

intermediate process of the squamosal dorsally. It can be seen in lateral view

Pro

REVISED DESCRIPTION OF MOSCHORHINUS 35

pdpPro Ic

PvpPro

ipOp

ioc pvfpp qpOp

tom Tipe Bs

O 38cm mpep

Fig. 15. Moschorhinus kitchingi. Occipital view.

(Fig. 16). The posterodorsal process forms most of the anterodorsal rim of the

post-temporal fenestra. This process tapers off from a relatively broad base

medially to a point jutting laterally, terminating in the lateral part of the roof of

the post-temporal fenestra. This process protrudes from under the intermediate

process of the squamosal anteromedially but, as it progresses laterally, it is

gradually covered by the intermediate process of the squamosal anteriorly. Its

posteromedial half is covered by the posterodorsal process of the opisthotic.

In lateral (Figs 16, 17) and ventral (Fig. 13) views, it can be seen that the

basal region of the prootic is in sutural contact with the basisphenoid. The

lateral suture runs diagonally from the floor of the braincase anterodorsally to

the fenestra ovalis posteroventrally. The anterodorsal part of the lip surrounding

the fenestra ovalis is formed by the basal region of the prootic (see Fig. 17).

As Mendrez (1972, 1974a) has remarked, the opisthotic and prootic are two

quite separate bones. A clearly distinguishable suture divides them. The

posterodorsal process of the opisthotic does not make contact with the lateral

border of the posterodorsal process of the prootic, nor is it visible in anterior

view as Mendrez (1974a) stated to be the case. The posterodorsal process of the

opisthotic covers the posteromedial half of the posterodorsal process of the

prootic posteriorly. In occipital view, one can observe within the post-temporal

fenestra a part of the suture dividing the posterodorsal processes of the prootic

and the opisthotic. This suture runs vertically for a short distance, skirting the

lateral border of the posterodorsal process of the opisthotic, and then curves

medially along its ventral border to where the posteromedial borders of the

posteroventral and posterodorsal processes of the prootic originate. Laterally to

396 ANNALS OF THE SOUTH AFRICAN MUSEUM

this, the suture divides the medial lip formed by the posteroventral process of

the prootic and the posteroventral flange of the paroccipital process of the

opisthotic. Ventrally to this medial lip, the suture that divides the posteroventral

process of the prootic from the anterodorsal flange of the opisthotic, runs

laterally. It can be traced posteriorly in the paroccipital fossa (Mendrez 1972:

203) and anteriorly between the anterodorsal flange of the paroccipital process

of the opisthotic and the posteroventral process of the prootic. The suture

curves first ventrally then medially along the border of the posteroventral

process of the prootic. The suture then skirts the base of the central process of

the prootic anteroventrally and the posterior corner of the dorsal lip of the

fenestra ovalis, before it enters the roof of the fenestra ovalis medially (see

lee, WY).

The concave, dorsal border of the prootic can be seen in lateral view,

curving posterodorsally to meet the medial border of the intermediate process of

the squamosal. The central part of the dorsal border of the prootic (dorsal limit

of the ‘lame dorsale’ of the prootic—Mendrez 1974a) contacts the supra-

occipital. The largest part of the ventral border of the lateral supraoccipital fossa

is formed by the dorsal border of the prootic. (This fossa is discussed below. )

OPISTHOTIC (Figs 12-17)

The opisthotic contacts the exoccipital and basioccipital posteromedially,

the prootic anteromedially, the tabular, supraoccipital and squamosal dorsally,

the squamosal, pterygoid and quadrate laterally, and the stapes ventrally.

The opisthotic consists of a robust transverse bar—the paroccipital process,

a T-shaped ventromedial tuberosity—the internal process, and a small, flattened

dorsomedial projection—the posterodorsal process. This is the terminology

Mendrez (1972, 1974a, 1974b) used to describe the opisthotic.

The paroccipital process of the opisthotic is V-shaped in parasagittal

section. This V-shaped process is formed by two flanges joined anteroventrally.

The posteroventral flange is more massive than the anterodorsal flange. The

V-shaped cavity formed by these two flanges is the paroccipital fossa of the

opisthotic. This fossa can be seen in dorsal and occipital views (Mendrez 1972,

1974a, 1974b).

The paroccipital process is laterally subdivided into two processes that can

be distinguished in ventral view, viz: the mastoid process of the opisthotic

posteriorly, and the quadrate process of the opisthotic anteriorly (see Fig. 13).

The mastoid process is marked by a ventral ridge originating approximately

in the middle of the paroccipital process and terminating near the bulbous

lateral end of the mastoid process. This ventrolaterally curving ventral ridge

adds to the robustness of the mastoid process. The mastoid process is thickest

near its distal end where the ventral ridge terminates. The posterior margin of

the mastoid process marks the posteroventral border of the rim of the

paroccipital fossa. The posterolateral part of the mastoid process contacts the

squamosal laterally, whereas its anterolateral part is free. A shallow indentation

REVISED DESCRIPTION OF MOSCHORHINUS 397

doppf

Isfo ae |p

dvf

dpSq

eopc bspPt

kPs tso

virPt

alpSoc

adpPro

papEpt

crPro

pdpPro

pvpPro

cpPro

pasEpt avpPro_ ipro

O 3cm

Fig. 16. Moschorhinus kitchingi. A. Detail of left temporal region. B. Detail of left

temporal region.

398 ANNALS OF THE SOUTH AFRICAN MUSEUM

separates the mastoid and quadrate processes of the opisthotic and forms the so-

called roof of the middle ear (‘toit de ’oreille moyenne’— Mendrez 1974a). The

quadrate process of the opisthotic, which juts outwards anterolaterally, is

thinner, broader and longer than the mastoid process. It becomes broader

laterally, similarly to the mastoid process, to form a bulbous lateral end. The

quadrate process projects further laterally than the mastoid process. The pos-

terior third of the dorsolateral surface of the quadrate process of the opisth-

otic contacts the quadrate process of the squamosal and the anterior two-thirds

contact the posterior part of the quadrate ramus of the pterygoid. This can be

seen in lateral (Fig. 16) and dorsal (Fig. 12) views. The lateral surface of the

quadrate process of the opisthotic loosely articulates with the quadrate and its

anteroventral surface loosely contacts the stapes.

The anterodorsal flange of the paroccipital process (anterior wall of

the paroccipital process—Mendrez 1972) contacts the posteroventral process

of the prootic medially. This combined structure forms the posterior wall of

the pterygo-paroccipital foramen (seen in dorsal view), the ventral border

of the post-temporal fenestra and the anterodorsal border of the paroccipital

fossa (both seen in occipital view). The anterior ridge of the paroccipital

process, marking the anterior border of the opisthotic, originates at the

anterolateral edge of the quadrate process of the opisthotic and terminates

near the dorsal lip of the fenestra ovalis. The base of the central process of

the prootic and the dorsal lip of the fenestra ovalis (also formed by the

prootic) contact the anteromedial part of the opisthotic (see Fig. 17). The

suture dividing the prootic and opisthotic has already been described.

The opisthotic forms the posterior third of the fenestra ovalis. The suture

dividing the opisthotic and the basioccipital can been seen in ventral and occipi-

tal view. It emerges from the posteroventral corner of the fenestra ovalis and

then turns medially across the ventral surface of the lip of the fenestra ovalis

(Fig. 17). The suture then curves posteromedially behind the tuberculum

spheno-occipitale, runs around the internal process of the opisthotic and then

curves laterally after passing medially to the jugular foramen. On reaching the

posteroventral lip of the jugular foramen, the suture extends into the jugular

foramen in an anterodorsal direction.

The internal process of the opisthotic can be seen in ventral and occipital

views. It is formed by a ridge originating on the ventromedial part of the par-

occipital process, curving and expanding ventromedially and terminating as a

ventromedial tuberosity between the jugular foramen and fenestra ovalis. From

this tuberosity a thin anterolateral and thicker, blunter posteromedial extension

project. The posterior extension forms the ventral lip of the jugular foramen and

the anterior extension forms the posteroventral corner of the lip of the fenestra

ovalis (Fig. 17). There is a small groove dividing the anterior extension from the

medial part of the opisthotic that forms the posterior border of the fenestra

ovalis. Similarly the posterior extension is separated ventrally from the part of

the opisthotic that forms the anterior part of the roof of the jugular foramen by

REVISED DESCRIPTION OF MOSCHORHINUS 399

eopc

Fig. 17. Moschorhinus kitchingi. Detail of left fenestra ovalis.

a shallow groove (see Fig. 17). This groove runs from inside the jugular foramen

anteromedially, more or less parallel to the ventrolateral suture of the exoccipi-

tal, and terminates on the posteromedial surface of the paroccipital process. The

part of the opisthotic that is overlain by the posterior extension of the internal

process projects into the jugular foramen and, with the exoccipital posteriorly,

forms the roof of the jugular foramen. A short groove is present on the pos-

terior face of the ridge and tuberosity, ventral to the groove at the jugular

foramen (see Figs 13, 15).

In occipital view, the suture between the anterolateral part of the exoccipi-

tal and the posteromedial surface of the opisthotic can be seen. This suture runs

from inside the jugular foramen, around the exoccipital ventrolaterally, and

then dorsomedially. Also visible in occipital view is the suture dividing the

medial corner of the posterodorsal process of the opisthotic and the ventro-

lateral corner of the supraoccipital. It originates half-way along the dorsal

border of the exoccipital.

The posterodorsal process of the opisthotic (visible in occipital view) orig-

inates medially to the paroccipital fossa and the lip (formed by the postero-

ventral process of the prootic and the posteroventral flange of the par-

occipital process) covering the dorsomedial part of the paroccipital fossa. The

posterodorsal process of the opisthotic is a flat projection that curves dorso-

laterally. It forms the posteromedial surface of the post-temporal fenestra. Its

lateral border stretches as far medially as the lip covering the dorsomedial part

of the paroccipital fossa (a medial indentation separates these two structures).

The posterodorsal process of the opisthotic makes sutural contact along its

dorsomedial border with the supraoccipital. This suture continues in a dorso-

lateral direction as it follows the dorsal border of the posterodorsal process. The

suture dividing the supraoccipital and tabular originates half-way along this

border. Part of the dorsal border of the posterodorsal process contacts the

400 ANNALS OF THE SOUTH AFRICAN MUSEUM

ventral border of the tabular. The lateral border of the posterodorsal process

contacts the posteroventral part of the intermediate process of the squamosal.

The short ventral border of the posterodorsal process of the opisthotic contacts

the posterior part of the posterodorsal process of the prootic. The posterodorsal

process of the opisthotic is not visible in anterior view as Mendrez (1974a) has

observed in Moschorhinus kitchingi, SAM-—K118. It rather resembles the con-

dition found by Mendrez (19746) in Promoschorhynchus platyrhinus, RC 116,

where the posterodorsal process is completely covered anteriorly by the inter-

mediate process of the squamosal and the anterodorsal process of the prootic.

SQUAMOSAL (Figs 12-16)

The squamosal is a large, complex bone with several processes; the termin-

ology used by Mendrez (1972) will be used to describe these processes. The

squamosal makes contact with the parietal, interparietal, supraoccipital, prootic,

opisthotic and tabular medially, the pterygoid and epipterygoid anteriorly, and

with the jugal and quadrate laterally.

The major part of the posterior wall of the temporal fossa is formed by the

three large medial processes of the squamosal. The laterally sloping dorsal

border of the squamosal forms the posterodorsal border of the temporal fossa

and anterior part of the lambdoid crest. The three medial processes occur one

above the other (see Fig. 16). The anteroventral process (third squamosal

process—Crompton 1955) is separated from the intermediate process (second

squamosal process of Crompton) by the post-temporal fenestra. The inter-

mediate and dorsal processes (first squamosal process of Crompton) are

separated by the posterior fold forming part of the lateral supraoccipital fossa.

The medial part of the broad dorsal process of the squamosal covers the

posterolateral part of the parietal (see Fig. 12). The lateral surface of the dorsal

process is confluent with that of the parietal, as are their dorsal and ventral

borders. The dorsal process of the squamosal is fused to the tabular along most

of its posterior surface. Its ventral border is marked by the fold forming the

posterior part of the lateral supraoccipital fossa (see Fig. 16). Part of this fold is

occupied by the anterior extension of the interparietal, which contacts the

ventral border of the dorsal process posterodorsally.

In lateral view it can be seen that the dorsal border of the intermediate

process of the squamosal forms the ventral border of the above-mentioned fold

and contacts the posteroventral area of the part of the interparietal that is

laterally exposed. The anterior part of the intermediate process makes sutural

contact with the anterolateral process of the supraoccipital dorsally and with the

prootic ventrally. The medial part of the ventral border of the intermediate

process of the squamosal forms a V-shaped notch in which the posterodorsal

process of the prootic is wedged. This fused structure forms the dorsomedial

part of the roof of the post-temporal fenestra, whereas the dorsolateral part of

the roof is formed by the lateral part of the ventral border of the intermediate

process.

REVISED DESCRIPTION OF MOSCHORHINUS 401

In occipital view it can be seen that the medial part of the intermediate

process contacts the ventrolateral part of the tabular, and the dorsolateral part

of the posterodorsal process of the opisthotic ventromedially.

In lateral view the ventral border of the intermediate process can be seen. It

curves ventrolaterally in a crescent-shape, delimiting the dorsolateral rim of the

post-temporal fenestra, until it becomes the dorsal border of the anteroventral

process of the squamosal. The dorsal border of the anteroventral process forms

the lateral part of the pterygo-paroccipital foramen. The medial blade of the

anteroventral process of the squamosal (the prootic process of the squamosal—

Mendrez 1974b) is wedged into a V-shaped notch formed by the lateral part of

the central process of the prootic. The posteromedial border of the postero-

ventral process of the epipterygoid contacts the anteroventral process of the

Ssquamosal anteromedially. The whole anterolateral border of the anteroventral

process of the squamosal, except for its distal end, contacts the posteromedial

edge of the quadrate ramus of the pterygoid. This suture runs posterolaterally

from the contact between the posterior part of the posteroventral process of the

epipterygoid and the squamosal, to the suture connecting the squamosal and

opisthotic.

The laterally directed flange of the squamosal overlies most of the

opisthotic, the only contact formed being where their distal borders meet (see

Fig. 15). The ventrolateral part of the anteroventral process of the squamosal

(the quadrate process of the squamosal—Mendrez 1974b) contacts the dorsal

part of the posterolateral tip of the quadrate process of the opisthotic posterior

to the squamosal-pterygoid contact (see Fig. 16). This suture is visible anteriorly

to the quadrate notch in the squamosal. (This notch is described below.) The

ventrolateral part of the squamosal seen in occipital view is the mastoid process

of the squamosal. The suture connecting the dorsolateral border of the mastoid

process of the opisthotic to the ventromedial border of the mastoid process of

the squamosal is visible in occipital and ventral views. Except for these two

above-mentioned distal sutures and the suture with the posterodorsal process of

the opisthotic, the rest of the squamosal overlies, but does not contact, the

opisthotic. It thus forms the lateral parts of the roof of the pterygo-paroccipital

foramen and the roof of the paroccipital fossa.

A deep, dorsally directed quadrate notch of the squamosal is present

anteriorly, in the distal part of the squamosal; it houses the dorsal part of the

quadrate (see Fig. 16). This notch is surrounded by the jugal laterally, the pos-

terolateral part of the anteroventral process of the squamosal (which covers the

quadrate process of the opisthotic) anteroventrally and the thick lip formed by

the jugal process of the squamosal dorsally. A shallow indentation is present

anteroventrally to this notch in the bones covering the quadrate process of the

opisthotic, namely, the quadrate process of the squamosal and the posterior end

of the quadrate ramus of the pterygoid. This indentation, the quadrate recess of

the squamosal, is probably synonymous with that described by Kemp (1969) and

with the squamosal recess (‘recessus squamosal’) of Mendrez (1974a). The

402 ANNALS OF THE SOUTH AFRICAN MUSEUM

posterior part of the quadrate fits into this recess. The quadrates are lost in most

of the Moschorhinus specimens, because they were loosely articulating bones

with no sutural connections.

In occipital view the following features can also be seen: the posteroventral

border of the intermediate process of the squamosal curves ventrolaterally,

forming the posterolateral border of the post-temporal fenestra and part of the

posterolateral border of the paroccipital fossa. A ridge runs in a dorso-ventral

plane on the mastoid process of the squamosal laterally to its contact with the

opisthotic. A posteroventral facing indentation on the mastoid process of the

squamosal borders this ridge laterally. Ventrally to this indentation and ridge,

and medially to the posterior part of the quadrate, a notch is situated posteriorly

between the two lateral processes of the opisthotic.

The dorsolateral part of the squamosal (the jugal process) curves anteriorly

to join the posterior end of the jugal. Unfortunately, in those specimens studied,

the jugal arch is either lost or damaged to such a degree that a detailed descrip-

tion is impossible.

SUPRAOCCIPITAL AND INTERPARIETAL (Figs 14, 15)

Both the supraoccipital and the interparietal are visible in occipital and

lateral view. In occipital view, the broad supraoccipital contacts the interparietal

dorsally, the tabulars dorsolaterally, the posterodorsal processes of the opis-

thotics ventrolaterally and the exoccipitals ventrally. The exoccipitals cover the

ventromedial part of the supraoccipital, except for a narrow gap between

the exoccipitals where the supraoccipital forms the dorsomedial part of the roof

of the foramen magnum. The suture between the tabular and supraoccipital runs

diagonally in a dorsomedial direction from its origin at the junction of the ven-

tral borders of the tabular and supraoccipital, to the dorsal border of the

supraoccipital. The suture between the ventral border of the interparietal and

the dorsal border of the supraoccipital is horizontal and short. A large, deep

occipital indentation is present in the region of the interparietal. Two smaller,

ventral indentations, forming part of the larger indentation, are present on

the dorsal part of the supraoccipital. These flank a short ridge originating in

the middle of the dorsal part of the supraoccipital and continuing dorsally on

the interparietal.

In occipital view, the interparietal is a small, laterally ovate bone bordered

ventrally by the supraoccipital, laterally by the tabulars and dorsally by the

parietal.

The aforementioned occipital indentation causes the interparietal, parietal,

medial part of the tabular, and the dorsal part of the supraoccipital to be set

deeper than the rest of the surrounding elements. This indentation was for the

attachment of certain neck muscles.

In lateral view, ventral to the posteromedial angle of the temporal foramen

(Mendrez 1974a: 80), is the lateral supraoccipital fossa, a large oval indentation

bordered dorsally by the parietal, whose ventral border forms a concave over-

REVISED DESCRIPTION OF MOSCHORHINUS 403

hang. The ventral border of this fossa is formed by the concave dorsal edge of

the anterodorsal process of the prootic, and the anterior border by the antero-

ventrally curving posterior edge of the posterodorsal process of the epi-

pterygoid. The fossa tapers off posteriorly into a short, horizontal fold. The

anteromedial part of the intermediate process of the squamosal forms the pos-

terior border of the fossa and the ventral part of its posterior fold. The dorsal

border of this fold is formed by the ventral border of the parietal and the dorsal

process of the squamosal. The dorsal venous foramen is situated in the anterior

region of this fossa.

The anterior extensions of the supraoccipital and interparietal are visible

within the lateral supraoccipital fossa. The anterolateral process of the supra-

occipital lies at a more medial level than any of the surrounding elements,

forming the medial wall of the lateral supraoccipital fossa. The anterolateral

process of the supraoccipital contacts the parietal dorsally, the posterodorsal

process of the epipterygoid anteriorly, the anterodorsal process of the prootic

ventrally, the intermediate process of the squamosal posteroventrally, and the

anterior extension of the interparietal posterodorsally. The dorsal venous

foramen is visible ventral to the epipterygoid-supraoccipital contact and anterior

to the prootic-supraoccipital contact.

The anterior extension of the interparietal fills the posterodorsal corner of

the lateral supraoccipital fossa. The interparietal is triangularly shaped and con-

tacts the anterolateral process of the supraoccipital anteroventrally, the dorsal

border of the intermediate process of the squamosal posteroventrally, the

ventral border of the parietal anterodorsally, and the ventral border of the

dorsal process of the squamosal posterodorsally.

PARIETAL (Figs 12, 14-16)

The parietal forms the posterodorsal part of the skull. It contacts the squam-

osal and tabular posteroventrally, the prootic and epipterygoid ventrolaterally,

the postorbital anterolaterally, and the frontal anteriorly.

In occipital view the parietal is situated between the dorsomedial borders of

the tabulars and the dorsal border of the interparietal. Its dorsal border is in

confluence with those of the tabular and squamosal. These borders form the

ventrolaterally curving, dorsal border of the occiput.

The parietal has a pronounced sagittal crest. The anterodorsal rim of the

temporal fossa is formed by an acute curving ridge on the posterodorsal and

dorsolateral surfaces of the postorbital (see Fig. 12). These postorbital ridges

bow posteriorly and are continued on the dorsomedial surface to produce the

sagittal crest. The sagittal crest is widest at its origin, anterior to the parietal

foramen. Posteriorly it becomes narrower and splits into two posterolaterally

flaring lambdoid crests, which form the dorsomedial border of the occiput pos-

teriorly and part of the posterodorsal rim of the temporal fossa laterally.

The parietal, in dorsal view, has an hour-glass shape. It is broad and robust

anteriorly, constricted in the middle above the epipterygoid, and forms two

404 ANNALS OF THE SOUTH AFRICAN MUSEUM

posterolaterally flaring flanges that form the anterior parts of the lambdoid

crests.

The broad anterior part of the parietal contacts the frontal and postorbitals

(see Figs 12, 14, 16). In dorsal view, it can be seen that the suture between the

posterodorsal border of the frontal and the anterodorsal border of the parietal

has a zig-zag arrangement. The anteroventrally sloping area between the

anterior border of the parietal and the parietal foramen, i.e. the broad origin of

the sagittal crest, is corrugated. In BP/1/4636, four small but distinct parasagittal

ridges are present in this region. The two medial ridges join up with the sagittal

ridge of the frontal anterior to them. This sagittal ridge runs on the dorsal

surface of the skull, from the middle of the nasals, over the frontals, and joins

the medial ridges of the parietal, which terminate on the slope anterior to the

parietal foramen.

The posteromedial flange of the postorbital and the anterolateral part of the

parietal are separated by a suture that can be seen in dorsal and lateral view.

The parietal foramen for the pineal organ is situated in the anterior part of

the sagittal crest, on the same level as the posterior border of the posteromedial

flange of the postorbital (see Fig. 12). The external opening of the parietal

foramen is a narrow spindle-shaped slit, similar to the condition in the

Moschorhinus specimens described by Brink (1959) and Mendrez (1974a).

In lateral view, the vertically curving suture between the dorsal process of

the squamosal and the posterior flange of the parietal can be seen. This suture

closely reflects the occipital suture between the parietal and interparietal and the

tabular. The ventral border of the parietal forms the roof of the braincase. The

anterior third of the ventral border of the parietal does not make sutural contact

with any bony elements, since this part of the braincase was unossified. The

middle part of the parietal is triangular in cross-section. The lateral edges of the

ventral border of this triangle contact the dorsal border of the epipterygoid and

the dorsal part of the anterolateral process of the supraoccipital on each side.

The short ventrolateral descending flange of the parietal overlaps the anterior

two-thirds of the dorsal border of the epipterygoid. The posterior part of the

ventral area of the parietal contacts the dorsal border of the interparietal. The

ventrolateral edge of the parietal, posterior to its suture with the epipterygoid,

forms the dorsal border of the lateral supraoccipital fossa.

EXOCCIPITAL (Figs 12, 13, 15, 17)

In occipital view, it can be seen that the exoccipital contacts the

posteroventral part of the supraoccipital dorsally, the posteromedial part of the

opisthotic laterally, and the posterior part of the basioccipital ventromedially.

The concave medial side of the exoccipital forms the lateral wall of the foramen

magnum.

The exoccipital is divided externally into a flat anterodorsal part and a

posteroventral boss. The ventrolateral half of the anterodorsal part overlaps the

posteromedial part of the opisthotic and the dorsolateral half contacts the

REVISED DESCRIPTION OF MOSCHORHINUS 405

posteroventral part of the supraoccipital. The anterodorsal part has two

pronounced, acute rims; one medially, the other ventrally. The medial rim

forms the dorsolateral lip of the foramen magnum. The ventral rim forms a

ridge demarcating the posterodorsal lip of the jugular foramen.

The posteroventral bosses of the exoccipitals form, together with the

posterior part of the basioccipital, the occipital condyle. The exoccipitals form

the dorsolateral parts of the occipital condyle and the basioccipital the ventral

third. The occipital condyle in BP/1/4636 has a central indentation on its

articular surface, not described before in Moschorhinus (Figs 12, 15). This

indentation involves the posterodorsal part of the basioccipital third of the

condyle and the posteromedial parts of the exoccipitals. The indentation and the

associated lateral bosses hint at a double condyle condition, and are similar to

those described by Watson (1913). The suture dividing the exoccipital and the

basioccipital runs parasagittally from dorsomedially inside the foramen magnum

(see Fig. 12), over the dorsal rim of the occipital condyle, and diagonally to a

point ventrolaterally on the convex ventral rim of the occipital condyle. From

here the suture runs anteriorly for a short distance on the ventral surface of the

occipital condyle and then curves dorsolaterally, over the ventromedial lip of the

jugular foramen, from whence it plunges into the jugular foramen in an

anterodorsal direction. The dorsomedial side of the posteroventral boss of the

exoccipital forms the posterior part of the ventrolateral wall of the foramen

magnum (and the concave dorsomedial border of the occipital condyle), and its

posterodorsal rim demarcates the posterior border of the foramen magnum. The

ventrolateral side of the posteroventral boss forms the ventrolateral border of

the occipital condyle, and the anterior border of the ventrolateral side forms the

posterior lip of the jugular foramen (Fig. 13). Near the mouth of the jugular

foramen, the lateral wall of the posteroventral boss is penetrated by two small

foramina for the hypoglossal nerve (XII) (see Fig. 17).

BASIOCCIPITAL (Figs 12, 13, 15-17)

The basioccipital forms the posterior part of the basicranium and the

ventral part of the occiput. In ventral view, the basioccipital contacts the

basisphenoid anteriorly, the opisthotic laterally, and the exoccipitals

posterolaterally.

The anteroventral part of the basioccipital and the posteroventral part of

the basisphenoid form the two spheno-occipital tubercles. The suture between

the anterior border of the basioccipital and posterior border of the basisphenoid

can be seen in ventral view. It dips diagonally in an anteroventral direction from

the ventral lip of the fenestra ovalis, curves medially, and surrounds the

posterior part of the spheno-occipital tubercle. The suture in the indentation

between the two tubercles is set further posteriorly than those parts that bisect

the tubercles.

Of the four elements that form the lip surrounding the fenestra ovalis,

viz: the basioccipital, opisthotic, basisphenoid and prootic, the basioccipital

406 ANNALS OF THE SOUTH AFRICAN MUSEUM

contributes least to the formation thereof after the basisphenoid (see Fig. 17).

Posterolateral to each spheno-occipital tubercle occurs the small laterally

directed process of the basioccipitals that forms part of the ventral lip of the fen-

estra ovalis. This small process is wedged between the posterolateral corner of

the basisphenoid anteriorly and the anterior border of the internal process of the

opisthotic posteriorly.

The suture between the internal process of the opisthotic and the basioccipi-

tal has a roughly diagonal arrangement. Seen in ventral view, it emerges from

the fenestra ovalis and runs medially across its ventral surface for a short dis-

tance. The suture turns posteromedially and skirts the anterolateral extension of

the internal process of the opisthotic, then curves slightly posterolaterally

around the ventromedial tuberosity and the posteromedial extension of the

internal process of the opisthotic.

Between the posterior border of the internal process of the opisthotic and

the posteroventral edge of the occipital condyle, a short parasagittal flange sep-

arates the ventrolateral border of the basioccipital and the ventromedial border

of the occipital boss of the exoccipital. This suture can be seen in ventral view.

The posterior part of the basioccipital has a rugose ventral surface. This

rectangular part of the basioccipital, situated posteriorly to the level of the jugal

foramina, forms the convex base of the occipital condyle.

In dorsal view, the posterior part of the basioccipital that participates in the

formation of the occipital condyle is visible as a thin strip flanked by the postero-

ventral bosses of the exoccipitals. The basioccipital is wedge-shaped in occipital

view; the broad concave base of the wedge is formed by the ventral surface of

the basioccipital. The suture between the basioccipital and exoccipital has been

described above.

DISCUSSION

In his paper on the Scaloposauridae, Crompton (1955) describéd a fused

periotic and mentioned that Olson (1944) had not found any dividing suture in

the periotic of those therocephalians he had studied either. The specimen known

as “Therocephalian A’ (Olson 1944) was discovered in the Tapinocephalus zone.

Its locality (Boonstra 1969; Kitching 1977) and size indicate that it is most prob-

ably a pristerognathid. Olson (19385) described this specimen as having a

periotic, but Boonstra (1954) and Van den Heever (pers. comm.) found a

prootic and opisthotic in the Pristerognathidae. It has been shown by Van den

Heever & Hopson (1982) that ‘Therocephalian B’ (Olson 1944) is actually a gor-

gonopsian. Olson (1944) described a periotic in this specimen, as well as in the

other gorgonopsians he studied. Authors such as Sigogneau (1970, 1974)

described a prootic and opisthotic in the Gorgonopsia. However, it is possible

that, in certain adult Gorgonopsia and Pristerognathidae, the suture between

the prootic and opisthotic is difficult or impossible to detect in the region sur-

REVISED DESCRIPTION OF MOSCHORHINUS 407

rounding the fenestra ovalis, but the co-ossification of these elements is not

complete enough to consider these groups as having a periotic. The Scalopo-

sauridae also have an opisthotic and prootic as described by Mendrez (1972),

and not a periotic as Crompton (1955) described. Neither the Whaitsiidae (pers.

obs.) nor the Moschorhinidae have a periotic, a clearly distinguishable prootic

and opisthotic being present. It seems quite clear that the Therocephalia have a

prootic and opisthotic, and not a periotic.

The pterygoid process of the quadrate, as it is described by Mendrez

(1974a), is actually not part of the quadrate but is the posterior end of the quad-

rate ramus of the pterygoid. The quadrates have been lost in the Moschorhinus

kitchingi specimen described by Mendrez (1974a) and the specimens described

here.

Judging from the shape of the squamosal recess, the quadrate was a rela-

tively large, broad bone, approximately the same shape and size as that

described by Mendrez (1974b) in Promoschorhynchus platyrhinus. In contrast to

the condition understood in Promoschorhynchus, the quadrate in Moschorhinus

seems to have had a small dorsal process that fitted into the quadrate notch of the

squamosal (described below). This notch and slot arrangement allowed the qua-

drate to articulate with the squamosal in a hinge-like manner. The quadrate lay

upon the quadrate process of the squamosal and the lateral tip of the quadrate

process of the opisthotic that is not covered by the squamosal or pterygoid.

The shape of the quadrate notch of the squamosal indicates that the

quadrate had a posterolaterally directed process that articulated medially with

the lateral end of the quadrate process of the opisthotic and the quadrate

process of the squamosal, and posteriorly with the posterior wall of the quadrate

notch that is formed by the squamosal. This process is probably synonymous

with the ‘squamosal process of the quadrate’ described by Mendrez (19745) in

Promoschorhynchus platyrhinus. The posteroventral part of the quadrate

probably contacted the squamosal in the same manner as in Promos-

chorhynchus. If this was the case, the stapes would be longer than Mendrez

(1974a) indicated in Moschorhinus kitchingi, and would extend laterally past the

lateral end of the opisthotic. The lateral side of the quadrate would have

contacted the medial part of the quadratojugal. Because of the absence of the

stapes and quadratojugal, it is not possible to describe the relations between

these elements and the quadrate.

In her paper on Moschorhinus, Mendrez (1974a) referred to the opening

dorsal to the posterior apophysis of the epipterygoid and the anterodorsal

process of the prootic as the ‘foramen veineux’. It would seem that the dorsal

part of the anterodorsal process of the prootic is damaged in her specimen. The

posterior foramen of the epipterygoid and dorsal venous foramen are separated

by the anterodorsal process of the prootic. This process is expanded dorsally to

contact the supraoccipital and the posterodorsal process of the epipterygoid.

(The term ‘dorsal venous foramen’ is preferred to venous notch—Boonstra

1934; Cox 1959; dorsal notch—Mendrez 1972; and venous foramen— Mendrez

408 ANNALS OF THE SOUTH AFRICAN MUSEUM

1974b, because it is a foramen completely surrounded by bone, and distinguishes

between the two above-mentioned venous foramina.)

The root of the trigeminal nerve (V) exits through the incisura prootica into

the cavum epiptericum, which housed the trigeminal ganglion. From this

ganglion the three trigeminal rami branched. The ramus opthalmicus passed

mesial to the processus ascendens of the epipterygoid into the orbit. The ramus

maxillaris and ramus mandibularis passed posterior to the processus ascendens

into the temporal cavity (see Presley & Steel 1976). Certain authors (Brink

1957; Mendrez 1972, 1974a, 1974b) argue that the posterior apophysis of the

epipterygoid divided these two rami. Others (Watson 1920; Kemp 1972) argued

that both rami emerged through the foramen dorsal to the posterior apophysis

(the posterior foramen of the epipterygoid). Crompton (1955) proposed a third

alternative, namely that both rami emerged ventral to the posterior apophysis.

The greatest part of the cavum epiptericum (and therefore also the trigeminal

ganglion) lies below the level of the posterior foramen of the epipterygoid. Since

the ramus maxillaris must have been directed ventrally, as is the ramus

mandibularis, it is unlikely that it would first be deflected dorsally from the

ganglion to pass through the posterior foramen of the epipterygoid and then

ventrally towards the maxilla. It is more feasible that the ramus maxillaris

passed, together with the ramus mandibularis, ventral to the posterior

apophysis.

The root of the abducens nerve (VI) usually exits through a foramen in the

base of the anteroventral process of the prootic (ossified pila antotica) (see

Haughton 1918; Goodrich 1958; Starck 1979). In Moschorhinus (Mendrez

1974a; pers. obs.) and Promoschorhynchus (Mendrez 1974b) this foramen is

absent. Olson (1938a) mentioned that a foramen for the abducens nerve may be

absent in certain gorgonopsids and would, in this case, pass anterior to the

prootic. This seems to have been the case in Moschorhinus as well.

The root of the facial nerve (VII) exits through its foramen between the

central and ventral ridges of the prootic. No impression for the geniculate

ganglion (gasserian ganglion—Mendrez 1972) could be found on the lateral

surface of the prootic.

There is no separate glossopharyngeal foramen in Moschorhinus. The

glossopharyngeal (IX) exited through the jugular canal together with the vago-

accessory (X and XI). This is a common feature in the therapsids (see Watson

1911; Haughton 1918; Kemp 1979). The hypoglossal (XII) enters into the

jugular foramen through two foramina in its dorsomedial wall (see Fig. 17).

The primary head vein of Moschorhinus probably ran mesially to the epi-

pterygoid (see Goodrich 1958; Presley & Steel 1976), then laterally to the otic

capsule where it received the vena cerebralis media. This united vessel passed

ventral to the paroccipital process of the opisthotic (see Presley & Steel 1976). It

is postulated that the vena cerebralis media most probably exited through the

incisura prootica via the posterior foramen of the epipterygoid. The posterior

foramen of the epipterygoid coincides with the dorsal part of the incisura

REVISED DESCRIPTION OF MOSCHORHINUS 409

prootica, as the anteroventral border of the anterodorsal process of the prootic

forms the foramen’s posterior border (see Fig. 16). If the vena cerebralis media

passed through this foramen, it would be in line with the dorsal opening of the

pterygo-paroccipital foramen through which it would pass ventrally to join the

primary head vein. Many authors (Watson 1920; Parrington 1946; Cox 1959;

Fourie 1974) described a groove running from the pterygo-paroccipital foramen

to the incisura prootica (foramen for the trigeminal nerve—Parrington 1946).

Most authors since Watson (1920) have claimed that the vena capitis lateralis

ran in this groove, but it seems unlikely that this large vein could pass through

the small posterior foramen of the epipterygoid in Moschorhinus. Moreover, the

vena cerebralis media, which is a very important vein in extant reptiles (usually

ignored by these writers), must have left some trace on the lateral wall of the

prootic.

The vena capitis dorsalis, which was situated in the sinus canal in cynodonts

(Watson 1911), seems to have been expanded anteriorly to form a broad sinus

that was situated in the lateral supraoccipital fossa in Moschorhinus. This sinus

would have been confluent anteriorly with a vein that passed through the dorsal

venous foramen. The vena capitis dorsalis would have been connected to the

vein that passed through the pterygo-paroccipital foramen (probably the vena

cerebralis media) and the vein that passed through the post-temporal fenestra

(see Watson 1920; Parrington 1946; Cox 1959; Fourie 1974).

The internal carotid artery ran anteriorly, ventral to the paroccipital process

of the opisthotic, and entered the external opening of the parabasal canal. The

stapedial artery branched off from the internal carotid in the proximity of the

stapes. It probably ran in an anterodorsal direction in the depression below the

central ridge of the prootic towards the cavum epipterycum, where it ramified

into three branches, each of which accompanied a trigeminal nerve ramus (see

O’Donoghue 1920).

Moschorhinus has many primitive characteristics, such as large suborbi-

tal vacuities similar to those of the pristerognathids (see Boonstra 1969), a

gorgonopsid-like dentition (see Parrington 1955), and a robust skull compared

to other Therocephalia (see Crompton 1955; Romer 1956; Brink 1959). Its

epipterygoid is not as expanded, and therefore not involved to the same degree

in the formation of the lateral wall of the braincase as are those of Promoscho-

rhynchus (Mendrez 19746) or whaitsiids (Kemp 1972). No ossified ethmoid or

orbitosphenoid elements could be found, as in gorgonopsids (see Olson 1944;

Kemp 1969) or in whaitsiids (see Kemp 1972). Moschorhinus has large post-

temporal fenestrae compared to cynodonts (see Watson 1920; Romer 1969;

Kemp 1979), but this may be a characteristic peculiar to the Therocephalia (see

Kemp 1972) because they are also larger than those of primitive therapsids (see

Romer 1956).

Derived and advanced characteristics in Moschorhinus include the par-

occipital fossa of the opisthotic, which seems to be shared with all the other

therocephalians except the pristerognathids (see Hopson & Barghusen 1986).

410 ANNALS OF THE SOUTH AFRICAN MUSEUM

The epipterygoid and its relations with the surrounding bony elements are more

advanced in Moschorhinus than in primitive Therocephalia (see Boonstra 1934;

Crompton 1955; Mendrez 1972). Moschorhinus has a much larger epipterygoid

than the gorgonopsids, scaloposaurids or certain pristerognathids. Its epiptery-

goid makes sutural contact with the parietal and supraoccipital dorsally and the

prootic posterodorsally, thus forming a substantial part of the lateral wall of the

braincase. The posterior apophysis of the epipterygoid is present in certain

Therocephalia (see Brink 1957; Kemp 1972; Mendrez 1974b), but in Moschorhi-

nus it most probably made contact with the prootic, a condition unique amongst

the Therocephalia. The posterior foramen of the epipterygoid is shared with the

whaitsiids (see Kemp 1972). The venous notch of the primitive therapsids (see

Boonstra 1934; Olson 1937; Mendrez 1972) is closed anteriorly by the epiptery-

goid in Moschorhinus forming a venous foramen, as happens in whaitsiids (see

Kemp 1972).

Looking at all the above-mentioned characteristics it would seem that Mos-

chorhinus was more advanced than the pristerognathids or scaloposaurids. Mos-

chorhinus was more primitive than, but not ancestral to, the whaitsiids.

Moschorhinus has a more primitive palatine region (see Mendrez 1974a), large

suborbital vacuities, postcanines, and a robust skull. Theriognathus, on the other

hand, does not possess suborbital vacuities nor postcanines and has a more deli-

cate skull. Moschorhinus did not have an ossified orbitosphenoid or interorbital

septum as in whaitsiids. Its epipterygoid is also much smaller and participates

less in the formation of the lateral wall of the braincase (see Kemp 1972). The

posterior foramen of the epipterygoid may have a different function in Moscho-

rhinus than in whaitsiids, because in Moschorhinus it is formed differently and

the posterior apophysis in the whaitsiid described by Kemp (1972) obstructs the

passage between the posterior epipterygoid foramen and the pterygo-parocci-

pital foramen. In whaitsiids the posteroventral process of the epipterygoid

(quadrate ramus of the pterygoid—Kemp 1972) is also apparently much closer

to the prootic than in Moschorhinus.

Moschorhinus has too many derived characteristics to be a cynodont

ancestor. It has paroccipital fossae, large post-temporal fenestrae and suborbital

vacuities. It has few postcanine teeth, a small dorsal parietal foramen and, as in

all Therocephalia, no stapedial foramen (see Mendrez 1974a). Furthermore, the

posterior epipterygoid foramen is unique to the moschorhinids and the

whaitsiids, and not homologous to the cynodont trigeminal foramen.

ACKNOWLEDGEMENTS

I wish to thank Dr C. E. Gow and Prof. J. W. Kitching for their help and

advice, and my wife Juanita for typing the manuscript.

REVISED DESCRIPTION OF MOSCHORHINUS 411

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Crompton, A. W. 1955. A revision of the Scaloposauridae with special reference to kinetism

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DE BEER, G. 1937. The development of the vertebrate skull. Oxford: Oxford University Press.

Fouriz, S. 1974. The cranial morphology of Thrinaxodon liorhinus Seeley. Annals of the

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Haucuton, S. H. 1918. Some new carnivorous Therapsida, with notes upon the brain-case in

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Kemp, T. S. 1979. The primitive cynodont Procynosuchus: functional anatomy of the skull and

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Kemp, T.S. 1982. Mammal-like reptiles and the origin of mammals. London: Academic Press.

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KITCHING, J. W. 1977. The distribution of the Karoo vertebrate fauna. Memoirs. Bernard

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MENpDREZ, C. H. 1972. On the skull of Regisaurus jacobi, a new genus and species of Bauria-

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412 ANNALS OF THE SOUTH AFRICAN MUSEUM

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(Moschorhinidae) from the Daptocephalus-zone (Upper Permian) of South Africa.

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(36): 506-524.

REVISED DESCRIPTION OF MOSCHORHINUS

413

ABBREVIATIONS

adfpp —anterodorsal flange of the

paroccipital process

adpEpt —anterodorsal process of the

epipterygoid

adpPro —anterodorsal process of the prootic

aelIp —anterior extension of the

interparietal

alpSoc —anterolateral process of the

supraoccipital

Ang —angular

Art —articular

avpEpt —anteroventral process of the

epipterygoid

avpPro —anteroventral process of the prootic

avpSq —anteroventral process of the

squamosal

Bo —basioccipital

Bs —basisphenoid

bspPt —basisphenoid process of the

pterygoid

ce —cavum epiptericum

cpPro —central process of the prootic

crPro —central ridge of the prootic

D —dentary

dirPt —dorsolateral ridge of the pterygoid

doppf —dorsal opening of the pterygo-

paroccipital foramen

dpSq —dorsal process of the squamosal

dvf —dorsal venous foramen

Ec —ectopterygoid

Eo —exoccipital

eopc —external opening of the parabasal

canal

Ept —epipterygoid

F —frontal

fEpt —foot of the epipterygoid

fm —foramen magnum

fo —fenestra ovalis

10C —indentation in occipital condyle

Ip —interparietal

ipOp —ainternal process of the opisthotic

ipro | —incisura prootica

ipSq —intermediate process of the

squamosal

J —jugal

jf —jugular foramen

jpSq —Jjugal process of the squamosal

kPs —keel of the parasphenoid

IG —lacrimal

Ic —lambdoid crest

Isfo —lateral supraoccipital fossa

M —maxilla

mpOp —mastoid process of the opisthotic

mpSq —mastoid process of the squamosal

—nasal

Op — opisthotic

J? —parietal

Pal —palatine

papEpt —posterior apophysis of the

epipterygoid

parf —parietal foramen

pasEpt —processus ascendens of the

epipterygoid

pdpEpt—posterodorsal process of the

epipterygoid

pdpOp —posterodorsal process of the

opisthotic

pdpPro—posterodorsal process of the prootic

pfEpt —posterior foramen of the

epipterygoid

pfo —paroccipital fossa

Pm —premaxilla

Po —postorbital

ppOp —paroccipital process of the opisthotic

pr —parasphenoid rostrum

Prf — prefrontal

Pro —prootic

Pt —pterygoid

ptf —post-temporal fenestra

ptpf —pterygo-paroccipital foramen

pvipp —posteroventral flange of the

paroccipital process

pvpEpt —posteroventral process of the

epipterygoid

pvpPro —posteroventral process of the prootic

qnSq —dquadrate notch of the squamosal

qpOp —dquadrate process of the opisthotic

qr —quadrate recess

qrPt —dquadrate ramus of the pterygoid

Sm —septomaxilla

Soc | —supraoccipital

Sq —squamosal

SV —suborbital vacuity

al —tabular

tpPt |—transverse process of the pterygoid

tso —tuberculum spheno-occipitale

Vv —vomer

vidfP —ventrolateral descending flange of the

parietal

virPt —ventrolateral ridge of the pterygoid

vn —ventral notch

vrPro —ventral ridge of the prootic

VII | —foramen for the facial nerve (VII)

(XII) at the mouth of the jugular

foramen

BP/1 —Bernard Price Institute for

Palaeontology catalogue number

RC —Rubidge collection

SAM —South African Museum

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6. SYSTEMATIC papers must conform to the International code of zoological nomenclature (particu-

larly Articles 22 and 51).

Names of new taxa, combinations, synonyms, etc., when used for the first time, must be followed

by the appropriate Latin (not English) abbreviation, e.g. gen. nov., sp. nov., comb. nov., syn. nov.,

etc.

An author’s name when cited must follow the name of the taxon without intervening punctuation

and not be abbreviated; if the year is added, a comma must separate author’s name and year. The

author’s name (and date, if cited) must be placed in parentheses if a species or subspecies is trans-

ferred from its original genus. The name of a subsequent user of a scientific name must be separated

from the scientific name by a colon.

Synonymy arrangement should be according to chronology of names, i.e. all published scientific

names by which the species previously has been designated are listed in chronological order, with all

references to that name following in chronological order, e.g.:

Family Nuculanidae

Nuculana (Lembulus) bicuspidata (Gould, 1845)

Figs 14-15A

Nucula (Leda) bicuspidata Gould, 1845: 37.

Leda plicifera A. Adams, 1856: 50.

Laeda bicuspidata Hanley, 1859: 118, pl. 228 (fig. 73). Sowerby, 1871: pl. 2 (fig. 8a—b).

Nucula largillierti Philippi, 1861: 87.

Leda bicuspidata: Nicklés, 1950: 163, fig. 301; 1955: 110. Barnard, 1964: 234, figs 8-9.

Note punctuation in the above example:

comma separates author’s name and year

semicolon separates more than one reference by the same author

full stop separates references by different authors

figures of plates are enclosed in parentheses to distinguish them from text-figures

dash, not comma, separates consecutive numbers.

Synonymy arrangement according to chronology of bibliographic references, whereby the year is

placed in front of each entry, and the synonym repeated in full for each entry, is not acceptable.

In describing new species, one specimen must be designated as the holotype; other specimens

mentioned in the original description are to be designated paratypes; additional material not regarded

as paratypes should be listed separately. The complete data (registration number, depository, descrip-

tion of specimen, locality, collector, date) of the holotype and paratypes must be recorded, e.g.:

Holotype

SAM-—A13535 in the South African Museum, Cape Town. Adult female from mid-tide region, King’s Beach, Port Eliza-

beth (33°51’S 25°39’E), collected by A. Smith, 15 January 1973.

Note standard form of writing South African Museum registration numbers and date.

7. SPECIAL HOUSE RULES

Capital initial letters

(a) The Figures, Maps and Tables of the paper when referred to in the text

e398. 4). the Figure depicting C. namacolus... >. ..in C. namacolus (Fig. 10) . .:.’

(b) The prefixes of prefixed surnames in all languages, when used in the text, if not preceded by

initials or full names

e.g. Du Toit but A.L. du Toit; Von Huene but F. von Huene

e.g. Therocephalia, but therocephalian

Punctuation should be loose, omitting all not strictly necessary

Reference to the author should preferably be expressed in the third person

Roman numerals should be converted to arabic, except when forming part of the title of a book or

article, such as

‘Revision of the Crustacea. Part VIII. The Amphipoda.’

Specific name must not stand alone, but be preceded by the generic name or its abbreviation to initial

capital letter, provided the same generic name is used consecutively. The generic name should

not be abbreviated at the beginning of a sentence or paragraph.

Name of new genus or species is not to be included in the title; it should be included in the abstract,

counter to Recommendation 23 of the Code, to meet the requirements of Biological Abstracts.

J. F. DURAND

A REVISED DESCRIPTION OF THE SKULL

OF MOSCHORHINUS

(THERAPSIDA, THEROCEPHALIA).

TY.

- VOLUME 99 PART 12 MARCH 1991 | ISSN 0303-2515

em THSOM ages

OF THE SOUTH AFRICAN |

CAPE TOWN

INSTRUCTIONS TO AUTHORS

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ANNALS OF THE SOUTH AFRICAN MUSEUM

ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM

Volume 99 Band

March 1991 Maart

Part 12 Deel

GEOGRAPHY AND CLIMATOLOGY OF THE

LATE CARBONIFEROUS TO JURASSIC

KAROO BASIN IN SOUTH-WESTERN

GONDWANA

JOHAN N. J. VISSER

Cape Town Kaapstad

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D118

GEOGRAPHY AND CLIMATOLOGY

OF THE LATE CARBONIFEROUS TO JURASSIC

KAROO BASIN IN SOUTH-WESTERN GONDWANA

JOHAN N. J. VISSER

Department of Geology, University of the Orange Free State, Bloemfontein

(With 9 figures)

[Paper presented at the Palaeontological Society of southern Africa Symposium, Cape Town,

September 1986 |

ABSTRACT

The major late Palaeozoic to early Mesozoic basins of south-western Gondwana were

located on a platform partly surrounding a highland interior. A palaeo-Pacific Ocean formed

the margin of the platform. The Karoo Basin had an oblong shape with a long axis of more than

2 000 km but, following the late Palaeozoic glaciation, it changed in size to small enclosed

fluvial basins during the early Mesozoic. A migrating tectonic region, attributed to subduction

of the palaeo-Pacific plate, caused the shrinking of the basin.

The climate in the Karoo Basin during the late Carboniferous varied from polar to cold.

The early Permian cold stage showed distinct climatic fluctuations, resulting in glacials and

interglacials, and a short-term warm period during which part of the Prince Albert Formation

was deposited. Temperatures rose sharply during the late Permian and early Triassic. An

abnormal cold, wet, middle Triassic resulted in the deposition of the Molteno Formation.

During the late Triassic and early Jurassic, warm to warm desert conditions prevailed. Tectonic-

ally and geographically induced regional climatic patterns in the Karoo Basin were super-

imposed on global climatic trends. The basin was also consistently positioned at high to inter-

mediate latitudes, suggesting that the principle of uniformitarianism cannot be applied without

constraint.

CONTENTS

PAGE

RMtROGUCH OME eet ee ye ee Sere ano Ree ae eek nee as 415

alacOPCOsraphyerese eto een ae Meranda a Mit Bees fe 416

alacochimatolopyna arn hinge sare iad Re oe via ea a aN 425

CONCUSSIONS eRe eras ct RNs oh aa s Benes 429

ENE THOWMSUTSTUA TIONS 5 Se Ubi Gate Aa oo 50 Bom Enc oe 430

INCISIONS 5 008 6 weme eas CHEE Ch atm oOn Oe One ha 430

INTRODUCTION

Knowledge on the configuration of the late Carboniferous to Jurassic Karoo

Basin in space and time is absolutely necessary in understanding the distribution

of lithofacies, climatic zones, and biological provinces extending beyond the

domain of the southern African continent. At the present stage of our know-

ledge of the Palaeozoic, it is impossible to separate climatology from geography

(Spjeldnaes 1981). Furthermore, sedimentation in the Karoo Basin was primar-

ily controlled by the palaeoclimate and tectonism.

415

Ann. S. Afr. Mus. 99 (12), 1991: 415-431, 9 figs.

416 ANNALS OF THE SOUTH AFRICAN MUSEUM

The objectives of this study are to define the position of the Karoo Basin in

south-western Gondwana; to illustrate basin evolution from the late Carbonifer-

ous to the early Jurassic; to draw a macro-scale climatic curve for Karoo

sedimentation; and to focus attention on anomalous climatic—geographic

relationships.

For the palaeogeographic and palaeoclimatological analysis, raw data were

taken from Tankard et al. (1982), Smith (1984), Visser (1983, 1984, 1987) and

Anderson & Anderson (1985), as well as from field notes made by the author

over several years of study on Karoo rocks. The palaeogeographic reconstruc-

tions are based on palaeotopographic maps, sediment dispersal patterns,

thickness of stratigraphic units, depositional environments and lithofacies. In the

interpretation of the palaeoclimate, use was made of palaeolatitudinal maps

(Irving 1977; Smith et al. 1981; Hallam 1985) and the lithology of the Karoo

rocks, as well as their fossil content. Although maps based on palaeomagnetic

evidence suffer from considerable uncertainties in areas where reliable determi-

nations are scarce, the apparent polar wander curve for the late Carboniferous

to Jurassic shows a fairly consistent trend from various sources of literature.

A modified Gondwana reconstruction, based on one by Norton & Sclater

(1979), was used for south-western Gondwana. In this reconstruction the Falk-

land Islands were considered as part of a rotated microplate and were

repositioned alongside the Transkei coast of southern Africa to achieve a better

fit for the palaeomagnetics, geology and palaeontology between the two regions

(Mitchell et al. 1986; Visser 1987). In the palaeoclimatic reconstruction a pro-

visional stratigraphic time scale for the Karoo Sequence, based on fossil evi-

dence, depositional rates and isotopic age determinations, was used. However,

more refined age data are needed, particularly for the Ecca Group above the

Whitehill Formation, which forms a highly significant basin-wide climatic marker

at the end of the early Permian. The age of the Dwyka Formation was partly

taken from Loock & Visser (1985). The subdivision of the Palaeozoic and Meso-

zoic follows that of Harland et al. (1982), except for the Triassic where an

informal subdivision of ‘early’, ‘middle’ and ‘late’, based on climatic trends, is

used.

PALAEOGEOGRAPHY

Karoo Basin in south-western Gondwana

To understand the tectonic evolution of the Karoo Basin, it is essential to

briefly refer to the regional geography of south-western Gondwana during the

late Palaeozoic. This part of Gondwana consisted of southern South America,

southern Africa, Falkland Islands, East Antarctica, and other microplates in

West Antarctica (cf. Storey et al. 1988), as well as inundated microplates in the

southern Atlantic Ocean (Fig. 1).

South-western Gondwana consisted of an elevated continental interior (e.g.

Transvaal and Windhoek highlands) with trough-faulted, intracratonic basins

417

GEOGRAPHY AND CLIMATOLOGY OF THE KAROO BASIN

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418 ANNALS OF THE SOUTH AFRICAN MUSEUM

(e.g. Kalahari Basin). Southwards the uplands merged into a broad platform

region on which the major depositional basins (e.g. Parana, Karoo and Beacon

basins) were located. A prominent mountain belt (proto-Precordillera), formed

by the continued subduction of the oceanic palaeo-Pacific plate below the Gon-

dwana plate since the Devonian or early Carboniferous, separated the platform

region from the palaeo-Pacific Ocean (Lock 1980; Smellie 1981; Forsythe 1982).

As a result of possible underplating (cf. Park 1988), this tectonic zone migrated

northwards during the late Palaeozoic and early Mesozoic, until it reached the

present southern Cape.

Glaciated Dwyka Basin

Very little is known about the pre-Dwyka landscape, as a non-depositional

period of at least 30 Ma (end of Visean to the end of the Westphalian) preceded

Ye -_

Area of major \erosion

of Witteberg Group

Palaeo-escarpment

Mountainous region

Shallow sea

' \

Major drainage OX Subduction

yA XXX? RY

ae DOOYOO zone

Fig. 2. Pre-Karoo (late Carboniferous) geography (after Visser 1987).

Palaeolatitudes (at +310 Ma) after Smith et al. (1981). AFR = Africa,

SAM = South America, FI = Falkland Islands.

GEOGRAPHY AND CLIMATOLOGY OF THE KAROO BASIN 419

glacial sedimentation (Loock & Visser 1985). Continental uplands dissected by a

major river system, the later Kalahari Basin, and a fairly flat-lying basinal plain

in the south were probably the major morphological elements (Fig. 2). Sea-level

was low as a result of the global Namurian regression (cf. Veevers & Powell

1987) and in the south-western corner of the Karoo Basin, up to 200 m of lower

Carboniferous Witteberg strata were eroded from the plain’s surface (Visser &

Loock 1982). Drainage was westwards into a shallow sea arm, which can be

attributed to abortive rifting of this part of south-western Gondwana.

The Dwyka Basin, during maximum glaciation, consisted of an elongated

(>2 000 km) east-west depository extending into Antarctica (Fig. 3). It was

bounded on the north by highlands, extending from East Antarctica across

southern Africa to South America, and on the south by an alpine-type mountain

range (proto-Precordillera). The northern mountainous plateau probably

attained elevations of 2 000 to 3 000 m, whereas the alpine-type mountains were

about 1 500 m above sea-level (Martin 1981; Visser 1987). A palaeo-escarpment,

up to 400 m high, separated the northern highlands from the basin in the south.

The subsidiary intracratonic Kalahari Basin was fault controlled.

Both basin and highlands were completely ice covered for most of the time,

but the western sea arm probably only had a sea-ice cover during winter. During

two interglacials this sea transgressed eastwards, almost up to the Falkland

EAST ANTARCTICA

Magnetic South

+ Pole

FALKLAND

Shallow {¢ “AI SLANDS

sea

Major source area

|ce-f low

direction

500 km

Fig. 3. The Permo-Carboniferous Dwyka basin during maximum glaciation.

Palaeolatitudes (at +290 Ma) after Smith ef al. (1981).

420 ANNALS OF THE SOUTH AFRICAN MUSEUM

Islands, along the basin axis that was isostatically depressed by the weight of the

ice as well as accumulated glacial debris. At the beginning, ice flow into the

basin was mainly from the north and south. Where the ice flowed over bedrock,

its thickness at the basin centre was probably in the order of 4 000 m but later,

when the ice advanced over diamicton, its thickness decreased to about 1 000 m.

Ice thickness over the northern highlands at maximum glaciation varied from

about 2 600 to 3 000 m (Visser 1987).

The early Permian post-glacial basin shows rapidly changing geography

(Fig. 4). After ice retreat only small local ice caps remained on the highest

mountains. The inundation of large parts of south-western Gondwana can be

attributed to a combination of sea-level rise (Stavrakis (1986) suggested a rise of

100 to 150 m on deglaciation) and isostatic depression. Although post-glacial

rebound took place, the depth of isostatic subsidence was such that this uplift

did not elevate the sediment—water interface above sea-level.

The Irati Sea, which covered the Parana Basin, was in continuity with the

Whitehill sea in the Karoo Basin (Oelofsen 1981). An eastern limit for the

Whitehill sea is defined by the absence of black shales on East Falkland (pre-

SOUTH sais:

Shallow sea

Fluvial and deltaic

deposition

Region of isostatic

rebound

Fig. 4. Post-glaciation (+260 Ma) palaeogeography of the Karoo Basin and surrounding areas.

Shoreline of the Irati and Whitehill seas modified after Oelofsen (1981). Palaeolatitudes after

Smith et al. (1981).

GEOGRAPHY AND CLIMATOLOGY OF THE KAROO BASIN 421

rotation and drift), but the original extent of the sea to the south-west is

unknown. The shallow seas had a typical fjord coastline in the north, whereas in

the south uplift along the proto-Precordillera caused northward regression of

shorelines, especially in South America. Water conditions ranged from fresh

through brackish to normal marine, depending on the rate of meltwater inflow

from the mountains. Isostatic rebound along sections of the northern highlands

caused extensive erosion of the glacial deposits and basement rocks. Debris was

deposited as deltaic and fluvial beds in fjord heads and shallow embayments

(Fig. 4) that were favourable for coal formation (Falcon 1986).

Epicontinental Ecca Basin

The large marine to non-marine basin formed a transition from an open

shelf to an enclosed basin with major source areas in the south, west and north

Source area

Palaeocurrent

direction

Fig. 5. The later Permian Ecca basin. Palaeolatitudes (at +255 Ma) after

Smith et al. (1981). NA = Namibia, BO = Botswana, ZI = Zimbabwe,

MO = Mogambique, FI = Falkland Islands, RSA = South Africa.

422 ANNALS OF THE SOUTH AFRICAN MUSEUM

(Fig. 5). Subsidence of part of the northern highlands led to large-scale inun-

dation of the region. Water depths in the south were up to 700 m (Kingsley

1981), although it was much shallower in the north. The bottom sediments con-

sisted mostly of black mud. The presence of abundant pyrite in the black shale is

also suggestive of highly reducing benthic conditions, probably well above the

water—sediment interface. Such a soft muddy bottom with toxic conditions

would have been unfavourable to a benthic fauna and, if such conditions were

associated with a low pH, the destruction of all organisms settling on the bottom

after death would have occurred. This could account for the scarcity of body

fossils in these rocks.

A new development in the basin evolution was the appearance of a source

area in the west that may be attributed to uplift caused by hot spot migration

(cf. Anderson 1982) preceding the break-up of Gondwana. The prominent

southern mountains, located a few hundreds of kilometres from the present

outcrop area of the Ecca Group, consisted of low-grade metamorphic rocks

Source area

Palaeocurrent

direction

\ 2 4 i

Flood-‘plain basin ;

-- /

Basin margin

Fig. 6. Early Triassic intracratonic Beaufort basins. Palaeolatitudes (at

+245 Ma) after Smith et al. (1981). NA = Namibia, BO = Botswana,

ZI = Zimbabwe, MO = Mocambique, RSA = South Africa,

FI = Falkland Islands.

GEOGRAPHY AND CLIMATOLOGY OF THE KAROO BASIN 423

associated with synorogenic intrusive and extrusive magmatic activity (Elliot &

Watts 1974; Kingsley 1981).

Intracratonic Beaufort basins

During the Triassic, south-western Gondwana underwent a dramatic change

in basin evolution with the formation of enclosed intracratonic basins. In

addition to the major Karoo Basin in the south, a much smaller one developed

in northern Zimbabwe (Fig. 6). The true extent of the basins will never be

known, except where prominent highlands defined their margins. These fluvial

basins had a largely centripetal drainage but the size of the rivers depositing the

widespread flood-plain muds and silts suggests there must have been a basin

outflow, probably towards the north-west and west (Botswana and northern

Namibia?), where the most distal fluvial facies were deposited. However, these

sediments are not fully preserved, as they were probably removed by uplift and

erosion during the pre-Stormberg hiatus.

Fluvial

Pv ial

basin /

Source area

Palaeocurrent

direction

Basin margin aes

SOugherm we

Range?

Fig. 7. Middle to late Triassic fluvial Stormberg basins. Palaeolatitudes

(at +225 Ma) after Smith et al. (1981). NA = Namibia, BO = Botswana,

ZI = Zimbabwe, MO = Mocambique, RSA = South Africa,

FI = Falkland Islands.

424 ANNALS OF THE SOUTH AFRICAN MUSEUM

Plate tectonics in the far south greatly influenced the palaeogeography.

Crustal deformation and uplift migrated northwards so that during Beaufort

deposition prominent mountain ranges were then located close to the present

southern African coastline. Crustal uplift in the west also resulted in basinward

migration of source areas.

Fluvial Stormberg* basins

An erosional period of up to 10 Ma separated the fluvial Stormberg sedi-

mentation from the underlying Beaufort beds in the south. During this period

large areas were probably stripped of their Beaufort sediment cover. The Storm-

berg beds were deposited in small isolated fault-controlled basins (Fig. 7) with

mountainous sources located mostly in the south-east, east and north. Typical

Major wind

direction

Basin margin

Fig. 8. The early Jurassic aeolian Stormberg Basin. Palaeolatitudes (at

+205 Ma) after Smith et al. (1981). NA = Namibia, BO = Botswana,

ZI = Zimbabwe, MO = Mocambique, RSA = South Africa,

FI = Falkland Islands.

* The term ‘Stormberg’ is informally used for the combined Molteno, Elliot and Clarens

formations.

GEOGRAPHY AND CLIMATOLOGY OF THE KAROO BASIN 425

thick clastic wedges accumulated at depocentres that showed a progressive shift

towards the east and north (Visser 1984). The noticeable absence of deposition

in the west may be attributed to those regions preceding break-up of Gondwana.

The mountainous sources in the south-east had an elevation of up to

4000 m (Turner 1975) and were initially drained by predominantly braided

streams during deposition of the Molteno Formation and by meandering streams

at a later stage. The distal fluvial facies of these stream systems probably

accumulated in Okavango-type swamps in the west (Visser 1984).

Aeolian Stormberg Basin

During the early Jurassic, fluvial sedimentation was largely replaced by

aeolian deposition over a large part of south-western Gondwana, as a result of a

climatic change (Fig. 8). The lateral extent of the aeolian basin margin is highly

speculative, as deposition was independent of the palaeoslope. Westerly winds

reworked and transported the unlithified fluvial sediments (including the distal

facies) of the Stormberg basins (Visser 1984). The highlands in the south-east,

east and north formed a barrier to the transportation of sand and airborne silt.

This resulted in thick accumulations of sediment on the windward side of the

uplands.

PALAEOCLIMATOLOGY

Climatology is the net result of a number of integrated parameters (admis-

sion of solar energy, atmospheric composition, configuration of landforms and

ocean basins, sea-level, pole position, and oceanic and atmospheric circulation),

the relative importance of which we do not yet fully understand. In the dis-

cussion of late Palaeozoic and early Mesozoic climates, reference will be made

to some of these parameters, although those of extraterrestrial origin are not

dealt with. Furthermore, to simplify discussion, only polar, cold, temperate,

warm and warm desert climatic zones are referred to.

Carboniferous

Globally the early Carboniferous (320-360 Ma) had a warm climate with

small latitudinal gradients (Frakes 1979; Boucot & Gray 1982). No Karoo rocks

of this age were preserved and the upper part of the Witteberg Group thus

constitutes the only source of evidence for reconstructing the pre-Karoo

climatology, which appears to have been cool to cold (pers. comm. J. C. Loock;

Fig. 9). This conclusion is substantiated by a palaeolatitude of >60°S for the

region (Smith et al. 1981). Although global temperatures were apparently high

during the early Carboniferous, the proximity of the basin to the south pole and

the location of the pole largely over land, resulted in the anomalous climate of

this region. As suggested by Spjeldnaes (1981), it is suspected that the cold

climate was confined to a narrow zone around the pole during globally warmer

periods.

ANNALS OF THE SOUTH AFRICAN MUSEUM

426

STRATI-

COLD <—»WARM | GRAPHY

LITHOLOGY

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ology of the Karoo Basin.

Fig. 9. The middle Carboniferous to early Jurassic clima

GEOGRAPHY AND CLIMATOLOGY OF THE KAROO BASIN LOM

Global temperatures dropped during the late Carboniferous (286-320 Ma)

and the climate became cool and humid (Frakes 1979). Although there was a

period of non-deposition in the Karoo Basin during the late Carboniferous that

precludes climatological interpretation, some facts suggest the presence of a

polar to cold climate (Fig. 9). Pre-Dwyka palaeosols are noticeably absent, rock

fragments at the base of glacial deposits indicate blocky weathering and, on

parts of the basinal plain, very little erosion took place during the hiatus. These

phenomena suggest the existence of dry polar conditions without sufficient

moisture for major ice cap formation over the Karoo Basin and adjoining areas.

The location of the Karoo Basin at latitude 70° to 80°S and unfavourable atmos-

pheric circulation patterns (polar easterlies blowing over a vast interior plateau)

support such a climatic interpretation.

The duration of polar conditions is a matter of contention. Glacial sedi-

ments of Oligocene age (31 Ma) are preserved at McMurdo Sound, Antarctica,

and give an indication of the age of the Cainozoic glaciation (Harwood 1986).

By about 15 Ma ago the Antarctic Ice Sheet was well established and reached its

maximum about 6,5 Ma when its effects were recorded in southern South

America (Tyson 1986; Van Zinderen Bakker & Mercer 1986). South-western

Gondwana probably had its total maximum ice cover between the end of the

Westphalian and the Permo—Carboniferous boundary. If the 25 Ma period of

the Antarctic Ice Sheet build-up is used as a standard, then the onset of regional

polar conditions in south-western Gondwana could have occurred between 310

and 320 Ma (Fig. 9). At least during the lower part of the Namurian (+12 Ma),

the Karoo Basin and surrounding area were thus completely ice free, but sub-

jected to cold-climate weathering.

During the latest Carboniferous (Stephanian) when the Karoo Basin was

situated between latitudes 60° and 75°S (Fig. 3), extensive deposition of glacial

debris occurred. The diamictites and associated rock types are suggestive of a

temperate to subpolar glaciation. At that stage the pole was located over Ant-

arctica and the large continental ice mass resulted in overall stronger air

circulation patterns. Strong westerlies thus supplied abundant moisture main-

taining an extensive ice cover.

Permian

Globally the lower third of the Permian is considered to have been cold,

whereas the upper two thirds were temperate to relatively warm (Frakes 1979;

Hallam 1985). The early Permian (Asselian—Kungurian; 258—286 Ma) climate in

the Karoo Basin was very unstable, with alternating cold and temperate stages.

Glaciation continued for most of the time but the main ice thrust into the basin

was from the east at this stage, when the ice cap was situated over Antarctica.

As the basin was located at the unstable margin of the ice sheet, well-developed

interglacials are recognized (Fig. 9). Although the area lay between latitudes 50°

and 65°S (Fig. 4), the large Antarctic ice mass still had a profound effect on cir-

culation patterns in the Southern Hemisphere. The abundance of dropstone

428 ANNALS OF THE SOUTH AFRICAN MUSEUM

argillite and the presence of wood fragments, together with a variety of fossils in

the interglacial beds, suggest cold water and the existence of subarctic woodlands.

The Prince Albert Formation was deposited during one of these short-term

warmer periods, but overall the climate was cold and wet (Fig. 9). Microflora

from the coal-bearing strata indicate fluctuating cool—cold temperatures with

cool temperate woodlands on exposed land areas (Falcon 1986). During this

stage a small ice cap could have been maintained over the highlands. Cool con-

ditions also prevailed during deposition of the lower part of the Whitehill

Formation, but then a dramatic climatic change to higher temperatures took

place (Fig. 9). Water temperatures rose sufficiently for reptiles (Mesosaurus) to

invade the Irati and Whitehill seas (Oelofsen 1981). Suitable explanations for

these short-term climatic fluctuations (third order Vail cycles) during the early

Permian are not yet available. It might be that global climate ameliorated in a

pulsating manner after the extensive Permo—Carboniferous glaciation.

The late Permian (Ufimian—Tatarian: 248-258 Ma) climate was warm and

seasonal with a savanna-type plant cover in the basin (Falcon 1986; Fig. 9). This

conclusion is substantiated by the appearance of reptiles on land, annual growth

rings in trees, and the presence of reddish palaeosols with calcrete nodules in the

lower Beaufort Group. At this stage the basin was situated between latitudes 50°

and 60°S and anticlockwise rotation of south-western Gondwana (strike of the

palaeo-Pacific margin changed from north-south to north—north-west to south—

south-west) probably accelerated the climatic change from cold to warm.

Triassic

Globally the Triassic climate was warm and probably seasonal, with atmos-

pheric circulation sluggish in the absence of polar ice caps (Hallam 1985). In the

Karoo Basin the early Triassic (Anisian and Ladinian; 231-248 Ma) climate was

also warm and very similar to that of the late Permian, except that it was

perhaps more equable (Tyson 1986). The basin was situated between latitudes

45° and 55°S (Fig. 6). At this stage the magnetic south pole was located over the

palaeo-Pacific ocean, and the orientation of the palaeo-Pacific margin of south-

western Gondwana changed from north—north-west to north-west. This caused a

partial obstruction of the flow of cold water towards the equator, which in turn

would have restricted the width of the cold circum-polar zone.

The apparent cold climate in the Karoo Basin during the middle Triassic

(Norian and Carnian; 219-231 Ma) was anomalous to the global pattern. A

sudden appearance of Dicroidium flora, an absence of red palaeosols and rep-

tilian fauna, and the change in fluvial systems during the deposition of the

Molteno Formation, suggest dramatic climatic changes. Unfortunately, the for-

mation unconformably overlies the Beaufort Group with a hiatus of about

10 Ma (Fig. 9). This prevents the recognition of any transition from a warm

early to a cold middle Triassic.

This dramatic drop in temperature is attributed to a change in tectonic style

of the Karoo Basin (small fault-controlled basins), severe uplift in certain

GEOGRAPHY AND CLIMATOLOGY OF THE KAROO BASIN 429

regions, and a rapid basinward displacement of the south pole (cf. Smith et al.

1981). Turner (1975) suggested that the southern mountain ranges, which were

situated at latitude 60°S, could have maintained small ice caps during this cold

and wet stage, which was, however, of very limited duration.

The late Triassic (Rhaetian; 213-219 Ma) was warm and dry. This is sug-

gested by the return of a reptilian fauna and the formation of reddish palaeosols

with calcrete nodules (Fig. 9). Climatic conditions were very similar to those of

the late Permian. The contact between the Molteno and Elliot formations is

transitional and implies a gradual change from a cold to a warm climate.

However, the interbedded coarse-grained sandstones near the base of the Elliot

Formation, which are identical to those of the Molteno Formation, are sugges-

tive of a change in temperature rather than a decrease in rainfall during the

beginning of the Elliot sedimentation.

Jurassic

Global climate during the Jurassic was warm and dry (Frakes 1979). This

conclusion is substantiated by the warm desert conditions prevalent in the early

Jurassic Karoo Basin (Fig. 9). The aeolian sandstones, flash-flood deposits and

greenish playa lake mudstones also point to the extreme aridity of the region.

This warm sand desert was located between latitudes 30° and 50°S (Fig. 8) and

suggests that overall climatic conditions during the Jurassic must have been

warmer than those of today. At this stage the strike of the palaeo-Pacific margin

of south-western Gondwana had changed to almost east-west and the southern

mountain ranges (part of the proto-Precordillera) obstructed moisture reaching

the interior. Dry westerlies were predominantly responsible for sediment trans-

portation in the interior desert.

Extensive volcanic eruptions started at about 200 Ma and altered the

regional climate profoundly (Tyson 1986). Although conditions were still warm,

rainfall probably increased considerably.

CONCLUSIONS

The Karoo Basin experienced an evolutionary tectonic pattern as a result of

plate subduction and uplift since the Devonian—Carboniferous along the palaeo-

Pacific margin of south-western Gondwana. This event determined the location

and altitude of the major source areas, the size of the basin, and the isolation of

the fluvial basins during the Mesozoic.

Regions of locally self-induced climate profoundly influenced life and

sedimentation in south-western Gondwana. These climatic anomalies can be

attributed to crustal uplift, isostatic depression, proximity to ice caps, and the

configuration of the land areas.

The palaeoclimatic reconstruction of the Karoo Basin shows that the prin-

ciple of uniformitarianism cannot be applied without constraint. Some of the

climatic anomalies can only be explained by globally warmer or colder periods

430 ANNALS OF THE SOUTH AFRICAN MUSEUM

than the present. This implies that present-day latitudinal climatic zones cannot

be uniformably projected for the Palaeozoic.

ACKNOWLEDGEMENTS

The author wishes to thank Johan Loock and Burger Oelofsen for fruitful

discussions on the early Carboniferous and early Permian climates, respectively.

Bruce Rubidge is thanked for critically reading an earlier draft of the manuscript.

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names by which the species previously has been designated are listed in chronological order, with all

references to that name following in chronological order, e.g.:

Family Nuculanidae

Nuculana (Lembulus) bicuspidata (Gould, 1845)

Figs 14-15A

Nucula (Leda) bicuspidata Gould, 1845: 37.

Leda plicifera A. Adams, 1856: 50.

Laeda bicuspidata Hanley, 1859: 118, pl. 228 (fig. 73). Sowerby, 1871: pl. 2 (fig. 8a—b).

Nucula largillierti Philippi, 1861: 87.

Leda bicuspidata: Nicklés, 1950: 163, fig. 301; 1955: 110. Barnard, 1964: 234, figs 8-9.

Note punctuation in the above example:

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JOHAN N. J. VISSER

GEOGRAPHY AND CLIMATOLOGY

OF THE LATE CARBONIFEROUS

TO JURASSIC KAROO BASIN

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