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FiscHER, P.-H., DuvAL, M. & Rarry, A. 1933. Etudes sur les échanges respiratoires des littorines. Archs

Zool. exp. gén. 74: 627-634.

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

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Konn, A. J. 19605. Spawning behaviour, egg masses and larval development in Conus from the Indian Ocean.

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

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(continued inside back cover)

ANNALS OF THE SOUTH AFRICAN MUSEUM

ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM

Volume 89 Band

June 1982 Junie

Part 2 Deel

PHOCID PHYLOGENY

AND DISPERSAL

By

CH. DE MUIZON

Cape Town Kaapstad

The ANNALS OF THE SOUTH AFRICAN MUSEUM

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PHOCID PHYLOGENY AND DISPERSAL

By

CH. DE MUIZON

Institut de Paléontologie, Paris

(With 9 figures and 1 table)

[MS accepted 11 February 1982]

ABSTRACT

An attempt at a cladistic phylogeny of the Phocidae is presented. Potamotherium and

Semantor are regarded as representatives of the sister group of the Phocidae, i.e. the

Semantoridae (= Semantorinae of Tedford 1976). The Phocidae are divided into Phocinae and

Monachinae and both subfamilies are subdivided into tribes, with every suprageneric taxon

defined by synapomorphies. Poorly known fossil phocines and most of the Paratethyan seals are

not taken into account, while some badly defined monachines are regarded as incertae sedis.

This phylogeny, which envisages tribal divisions, allows for new hypotheses about the original

homelands and southward migrations of the monachines. The Monachinae most probably

originated in Europe and the three tribes of the subfamily crossed the Atlantic Ocean by way of

the equatorial currents. One crossing is supposed for the Lobodontini and the Miroungini,

while two east to west crossings seem to characterize the Monachini. It is also suggested that

the southward migration of the Monachinae followed the Atlantic coasts of Africa and South

America, and the Pacific coast of South America.

CONTENTS

PAGE

| WaLaRoys Wren Olt chs ere os See. Goede So SOO Gc OO eRa TT nig orto os 176

Bhocidiphylogenyir ree nec cee crite er ori caee 176

Relationship of phocids to other Musteloidea............. 176

MhesPhocidaeres pact ct te ite Hopkin salient tid sec pesioe 182

IPH CHEN OCI ACIS Se er coers ica ore epee eiere ea ihe Sas eects ace 187

Phoca-Pusa—HalichOcrusm tcc ee ee eee 188

Cystophora—Pagophilus—Histriophoca...............+45 190

DISCUSSION Ra Nt ot cree PPO ore asntbersrasitle Raita aa 191

ihe Monachinac erty vyaon Wt arise oe aa etaiia cone settee 193

ihe Mon achint rye cpccke ere esky tech: petals waite eeren 197

ihe MViTrouncinietrib nove scree eon 199

Mheikobodontinien yee kote ae eit lene 200

DISCUSSION Sere, 2 Sb yeierpe trea ieters oncieka = epakoas! oar he AD Gs 202

Phocid' paleobiogeo graphy acter cc. sc erie Oo eel eipieieast: 202

INotthernjoreinofsmonachines: sere eon 203

Modevotidispersaly Aa iirermtoria hich chee nt tre eaoieieee 203

Origin and dispersal routes of monachine tribes........... 203

iheyMonachinie mc acecusters eve erence fata ara 203

iheIMirouncininery ey cee met ere emcee 206

MheMobod ontinik Mec nee Tone e oases aon: 206

Conclustonsiersasaas he presses crs ati yeast esac tanec eye ee 208

NAGE TIGUIN ee sey ec se teeer users Medes es cecdieve sole ines arcsec «eats pte eae 210

FAICKNOWIEASEMENtSep Ro erect cere eect aCe 210

IRCLELENICES spree reste eet ovs ety tte canoe tater A cid oisle lols Aerob AG 210

ITs)

Ann. S. Afr. Mus. 89 (2), 1982: 175-213, 9 figs, 1 table.

176 ANNALS OF THE SOUTH AFRICAN MUSEUM

INTRODUCTION

The problem of the pinniped relationships to other carnivores has been

abundantly discussed by various authors (e.g. Mivart 1885; Scheffer 1958;

McLaren 1960b; King 1964; Mitchell 1967; Mitchell & Tedford 1973; Sarich

1969a, 1969b, 1975). Tedford (1976) summarized the data of this problem and

reached the conclusion that the group is biphyletic. The pinnipeds (phocid and

otarioid seals) are included by Tedford in the infraorder Arctoidea. Within this

group the otarioid seals are more closely related to the parvorder Ursida and

the phocid seals to the parvorder Mustelida. The purpose of this paper is to

analyse the relationships within the Phocidae as defined by Tedford (1976)

(= Phocidae s./.). The problem of relationships of the phocids to the genera

Potamotherium and Semantor and to the lutrines, although frequently

considered by previous writers, will be briefly discussed; the relationships of

these musteloids to the other carnivores will not be considered here, having

been clearly outlined by Tedford (1976).

PHOCID PHYLOGENY.

RELATIONSHIP OF PHOCIDS TO THE OTHER MUSTELOIDEA

The study of Mivart (1885) represents the first record in the literature of a

discussion on phocid-lutrine relationship. In this work Potamotherium was

definitely considered to be a lutrine, which has been the opinion of most

authors since that time. In his study Mivart exposed several features that

closely relate seals to otters and otariids to bears, thus demonstrating for the

first time the polyphyletism of the pinnipeds. This idea is now almost uni-

versally accepted among palaeontologists. The features outlined by Mivart

(1885: 498) mostly concern the skull (orbitary and auditory region), the mand-

ible, and the femur.

Potamotherium valetoni (Lower Miocene of France) is so lutrine-like that it

was for a long time considered to be a very specialized otter. It is regarded as

such by Kellogg (1922) who ratifies Mivart’s arguments about lutrine—phocid

similarities and notes several characters of Potamotherium that ‘... may

indicate relationships with the Phocidae’, and concludes that ‘... one of the

forbears of Potamotherium was the source and that the Lutrinae and the

Phocidae are both descendants of that type’ (Kellogg 1922: 86). This definitely

anticipates the interpretation given here (Fig. 1).

The striking similarities of Potamotherium and the Phocidae have been

noted elsewhere. Some authors consider the resemblance to be of phylo-

genetical significance (Kirpichnikov 1955; McLaren 1960b; Mitchell & Tedford

1973; Tedford 1976), while others believe Potamotherium to be related to

lutrines, the phocid-like features of this aquatic carnivore being due to conver-

gence (among others, Thenius 1949a, 19496, 1969; Viret 1955, Piveteau 1961).

AT)

PHOCID PHYLOGENY AND DISPERSAL

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178 ANNALS OF THE SOUTH AFRICAN MUSEUM

Another frequently discussed phocid-like aquatic carnivore is Semantor

macrurus from the Upper Miocene of Pavlodar (Kazakstan). The phocid

features of Semantor macrurus are so striking that they led Orlov (1933) to

classify this form in a new family of Pinnipedia, the Semantoridae. Thenius

(1949b) regards the similarities between Semantor and phocids to be not as

numerous or as important as stated by Orlov, and he supports Friant (1947) in

ascribing them to convergence. However, many authors (Kirpichnikov 1955;

McLaren 1960b; Mitchell & Tedford 1973; Tedford 1976) have also argued that

these similarities are of phylogenetical significance.

Tedford (1976), in a cladistic analysis of the pinniped relationships, relates

the Semantoridae (in which he includes the genera Potamotherium and Seman-

tor) to the Phocidae, both being the sister group of the Mustelidae. Tedford’s

classification introduces a slight ambiguity because the Phocidae (sensu

stricto = sensu Simpson 1945 and Romer 1966) and the Semantoridae are

considered to be subfamilies. The Phocidae (sensu lato = sensu Tedford 1976)

include the Phocinae (s.J.), which correspond to the Phocidae (s.s. = sensu

Simpson 1945), and the Semantorinae (sensu Tedford 1976). The taxon Phoci-

dae now has two interpretations: s.J. (= sensu Tedford 1976) and s.s. (= sensu

Simpson 1945). Although Tedford’s classification is logical in a strictly cladistic

sense, both groups are, for the sake of convenience, here regarded as families.

Moreover, according to the interpretation of the relationships of the four

groups given here, Phocidae, Semantoridae, Lutrinae and other Mustelidae

(Fig. 1), the Lutrinae will be given family rank (i.e. Lutridae). This is an

application of the sequency process as defined by Nelson (1974). The four

families are grouped into the Musteloidea. Be that as it may, these terminologi-

cal points are considered to be of little significance here since the present study

focuses on the relationships of the groups cited above rather than their

classification.

Tedford (1976) has pointed out three characteristics that could define the

Semantoridae and the Phocidae:

(i) swimming mainly by flexion of the trunk,

(ii) dentition reduced to homeodonty,

(iii) an enlarged process for the teres major muscle, which occupies the lateral

border of this process.

These three features cannot all be regarded as synapomorphies. Among

the carnivores, swimming mainly by flexion of the trunk is found not only in

phocids but also in otters and this characteristic is, therefore, inappropriate as a

synapomorphy of Phocidae and Semantoridae. Homeodonty is also found

among carnivores in the Otariidae and represents a general tendency in all

toothed marine mammals. Furthermore, Potamotherium does not, in fact, have

a homeodont dentition, and that of Semantor is unknown. Therefore, this

characteristic is also an inadequate synapomorphy for the Phocidae and the

Semantoridae. The enlarged insertion for the teres major muscle of the phocids

PHOCID PHYLOGENY AND DISPERSAL 179

and Potamotherium is absent from all other carnivores, as clearly demonstrated

by Tedford (1976), and the teres process of these musteloids is very different

from the one observed in ursids and procyonids. Although the scapula of

Semantor is unknown, the enlarged insertion for the teres major muscle is

hypothetically regarded as a synapomorphy of phocid (s.s.) and semantorids.

The pelvis of the phocids (s.s.) is very typical and distinct from those of

other carnivores. The ilium is very short, wide, triangular shaped and extro-

verted, while the ischiopubis is very enlarged. Considering the coxal of Pota-

motherium, Savage (1957: 215) has already stated that it ‘more resembles

Phoca than Lutra’. In fact, the short outwardly flexed ilium, the weak symphy-

sis, and the long and dorsally elevated ischium enclosing a large obturator

foramen are definitely phocid-like and show in Potamotherium an obvious

tendency towards the phocid coxal condition. The coxal of Semantor is so

phocid-like that, if founded isolated, it would almost certainly be identified as a

primitive phocid. The ilium is even shorter and more extroverted than in

Potamotherium, and approaches more a primitive phocid condition than a

lutrid one. The enlargement of the ischiopubis, even longer than in some

Monachinae, and the pubic symphysis orientated downward are also typically

phocid-like. The coxal in otters is very different from that in Semantoridae. In

otters the ilium is always very long and the ischiopubis short (this condition is

especially well marked in the sea otter). In all otters, as in all terrestrial

carnivores, the ilium is longer than the ischiopubis or approximately of the

same size (see Taylor 1914, figs 10-12). In the Semantoridae and obviously in

the Phocidae, the ilium is always much shorter than the ischiopubis. These

conditions have been noted on all the coxae of semantorids and lutrids

examined during this study.

The femora of semantorids and phocids differ radically (as stated below),

the former having a second trochanter while it is always absent in the latter. In

this respect the similarity existing between the non-phocid carnivores (including

the semantorids) is regarded here as a symplesiomorphy. Nevertheless, the

femora of phocids and semantorids show a common apomorphic tendency to

develop an epicondylar ridge on the medial side of the distal extremity. This

tends to give an oblique position to the condylar surface of the distal extremity

of the femur relative to the axis of the bone [already observed by Savage (1957)

in Potamotherium]. In otters (including sea otters) the epicondylar ridge is

totally absent and, contrary to the phocid condition, this region of the femur is

somewhat concave; moreover, in otters the condylar surface is perpendicular to

the shaft of the bone. The tendency to develop an epicondylar ridge on the

semantorid femur bears resemblance to the S-shape of the medial border of the

phocid femur; in otters this border is C-shaped (in anterior view). These

conditions are related to the fact that the condyles of the femur seem to have

moved laterally and distally in the phocids and the semantorids, while the

movement is medial and proximal in otters (this is especially clear in the sea

otter, Enhydra lutris).

180 ANNALS OF THE SOUTH AFRICAN MUSEUM

Another similarity between the femora of phocids and semantorids is the

tendency for the size of the epicondyles to be strongly developed, while in all

otters the epicondyles are very little developed. As with the development of the

epicondylar ridge, this condition is related to an important use of the flexor and

extensor muscles of the foot (peroneus longus, extensor digitorum longus,

gastrocnemius caput laterale and caput mediale, flexor digitorum superficialis).

This clearly indicates that, as in the phocids, the movements of the foot were

essential in semantorid swimming. In the otters, the action of the foot is not as

important and the propulsive movement of the hind limb is a powerful

backward extension of the whole limb (see below), being, therefore, a more

generalized movement.

These two similarities between the femora of phocids and semantorids, i.e.

a tendency to develop an epicondylar ridge and to increase the size of the

epicondyles on the femur, are synapomorphic trends of the group.

As in the phocids, but to a lesser degree, Potamotherium and Semantor

show a tendency towards a shorter femur; in this respect these two genera are

closer to the phocids than to the lutrids.

The tibia of Semantor is typically phocid-like and the same could be said of

this bone as of the coxal—if found isolated it would have been classified as

belonging to a primitive phocid. It definitely differs from the lutrid tibia in

having its medial border very convex in its proximal third. This well-marked

convexity, where the popliteus is inserted, gives the tibiae of phocids and

Semantor an S-shape that is never seen in any otter. In this group the medial

side of the tibia is, on the contrary, deeply concave. The condition observed in

Potamotherium, although less marked than in Semantor, is similar and its tibia

resembles more closely that of Semantor than that of Lutra or Enhydra.

Although McLaren (1960b) stated that the tibia and fibula of Semantor

were fused proximally as in the phocids, Orlov (1933: 196) in his description

definitely noted proximally articulated bones.

As stated by McLaren (1960b), the talus of Semantor, as in phocids, has

lost the groove of the trochlea, which is usually well marked in the terrestrial

carnivores. Savage (1957) stated that the groove of the trochlea of Potamothe-

rium talus is shallower than in the lutrids, therefore approaching the phocid and

semantorid condition. However, both tali of Semantor and Potamotherium are

lacking the posterior process that is a typically phocid condition.

In the foot of Potamotherium miocenicum the MtV is so phocid-like that

one specimen from the Tortonian deposits of Neudorf (CSR) (Thenius 1950)

was at first referred by Toth (1944) to Miophoca vetusta. This misunderstanding

is indicative of the great similarity that exists between Potamotherium and the

Phocidae.

It is also worth noting that Potamotherium and Semantor have a long tail, a

character that seems to relate them to the lutrids (Thenius 1949b). However,

the tail of these musteloids is much shorter even than the short tail of the sea

otter (Enhydra lutris) which could approach that of a primitive terrestrial

PHOCID PHYLOGENY AND DISPERSAL 181

musteloid in size. The wing-like transverse process of the first three caudal

vertebrae of Potamotherium and Semantor is much less developed than in

lutrids and indicates less use of the tail in swimming. As indicated by Savage

(1957: 191), in aquatic mammals, where the primary organs of propulsion are

usually situated posteriorly, the tail and hind limbs develop in inverse propor-

tions. In Potamotherium and Semantor the little developed tail (compared to

otters) is in accord with an important use of the hind limb in swimming. As a

matter of fact, the anatomy of the semantorid hind limb indicates that it was

used in swimming, probably in a different way from that of the otters, but more

similar to that of the phocids. The swimming action of the hind limbs of otters

is an alternating or simultaneous paddling (Fischer 1939, and personal observa-

tions). This movement is made anteroposteriorly and the plane of the foot is

always approximately perpendicular to the sagittal plane of the animal. The

action of the limb is simply a full backward extension. When seals swim the

paddling of the hind limbs is always alternating, lateromedial, and the plane of

the foot is always parallel to the sagittal plane. One of the actions of the limb is

an adduction of the leg. In such swimming the feet are always posterior to the

pelvis. The adduction of the leg is facilitated by the enlarged ischiopubis and by

the torsion of the tibia and of the distal extremity of the femur, two conditions

that tend to place the tibia in front of the ischiopubis (the limb being orientated

backward). Such a position increases the lever arm of the adduction of the leg

and reinforces the action of the adductor muscles (semimembranosus, semiten-

dinosus, gracilis, and biceps femoris). The anatomy of the hind limbs of the

semantorids (mentioned above) clearly indicates a phocid-like use of these

limbs in swimming, which is a condition that separates the phocids and

semantorids from the lutrids. The conclusion of Helbing (1921) concerning

swimming in Potamotherium, although not very clear, seems to indicate a lesser

mobility of the femur and a more important role of the leg (tibia and fibula)

and of the foot than in the lutrines. This definitely agrees with the interpreta-

tion given here. All the similarities of the semantorids to the lutrids have most

probably to be considered as symplesiomorphies within the ‘phocid—semanto-

rid—lutrid’ group. So too must be considered the fairly well-developed tail of

the semantorids.

The Phocidae, the Semantoridae and the Lutridae constitute a monophyle-

tic group defined by the following synapomorphies:

(i) aquatic Musteloidea,

(ii) swimming by flexion of the posterior part of the spinal column, with the

hind limbs playing an important role.

The lutrid synapomorphies are not examined in detail, this group being

considered here only in its relation to the phocid-semantorid group. However,

it is worth noting that the clear tendency to increase the size and the power of

the tail could represent an important synapomorphy of the Lutridae.

The Semantoridae—Phocidae may be defined by at least five synapomor-

phies:

182 ANNALS OF THE SOUTH AFRICAN MUSEUM

(i) large insertion fossa for the teres major (?),

(ii) shortening of the ilium and enlarging of the ischiopubis,

(iii) tendency to develop an epicondylar ridge and to increase the size of the

epicondyles on the femur,

(iv) tendency to develop a popliteal angulation on the tibia,

(v) reduction of the trochlear groove of the talus.

The definition of the semantorid synapomorphies is problematical because

the anterior half of the skeleton of Semantor is largely unknown (one humerus

was referred by Kirpichnikov (1955) to Semantor, and perhaps belongs to the

holotype). Most of the synapomorphies of Potamotherium and Semantor are

either synapomorphies of the phocid—semantorid group, or symplesiomorphies

of the phocid—semantorid-lutrid group. Nevertheless, in view of the great

similarities between Potamotherium and Semantor, it is here tentatively con-

cluded that they belong to the same group. Moreover, Potamotherium, which

comes from the European Lower and Middle Miocene, is temporally well

situated to be on the lineage leading to Semantor from the Upper Miocene of

western Siberia. This is corroborated by the fact that the features cited above

are all more pronounced in Semantor. However, the presumed relationship of

these two musteloids will have to be confirmed by the discovery of new material

(in particular cranial material) of Semantor.

The present interpretation of the relationship of Potamotherium and

Semantor to the other Musteloidea differs from that of Thenius (1949a, 1949b,

1969, 1972) who relates them to the lutrids rather than to the phocids, as is

done in this paper. However, the opinion presented here is in agreement with

Kirpichnikov (1955), McLaren (19605), and Tedford (1976).

THE PHOCIDAE

The Phocidae (s.s.) are defined by three features, two of them are unique

among the mammals. In non-phocids the psoas major distal insertion is located

posteromedially on the second trochanter of the femur, while in the phocid it is

inserted on the ventral edge of the ilium on the posteroventral ischiatic spine,

just anterior to the iliopectineal eminence (Figs 2-3). This modification of the

psoas major distal insertion represents an adaptation to aquatic life in the

Phocidae (De Muizon 19816). The swimming of true seals is achieved by

alternating adductions of the hind limbs in conjunction with strong undulations

of the posterior part of the spinal column. Both movements are almost always

on a horizontal plane. The quadratus lumborum and the psoas minor (like the

psoas major) both have their proximal insertion on the ventral side of the

lumbar vertebrae, their distal insertion being on the ventral edge of the ilium;

when contracted alternatively, they emphasize the lateral flexion of the spinal

column. In the phocid swimming action, the insertion of the psoas major on the

ventral edge of the ilium obviously reinforces the horizontal undulatory

movements, while in terrestrial mammals the psoas major inserted on the

femur acts as a flexor of the thigh, which assists the forward movement of the

PHOCID PHYLOGENY AND DISPERSAL 183

Fig. 2. Left innominates in lateral aspect. A. Zalophus californianus (from Howell 1929).

B. Pusa hispida (from Howell 1929). C. Monachus monachus (from Ray 1976). Pmi—pos-

teroventral ischiatic spine where the insertion of the psoas major is located (in the Phocidae);

Pmni—iliopectineal eminence, where the insertion of the psoas minor is located.

ANNALS OF THE SOUTH AFRICAN MUSEUM

184

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PHOCID PHYLOGENY AND DISPERSAL 185

hind limb in walking and running. The psoas major insertion on the ilium, a

synapomorphy of the Phocidae s.s., is not found in the Semantoridae where the

second trochanter of the femur, absent in the Phocidae, is always present.

In other respects the talus of the Phocidae shows a very strong posterior

process of the corpus tali, which has a groove on its plantar aspect indicating

the passage of the flexor hallucis longus tendon. This condition is due to the

very important action of the flexor hallucis longus in phocid swimming. During

the adduction of the leg, which takes place in the alternating movement of the

hind limb, this muscle prevents the flexion of the foot and the extension of the

fingers; this causes resistance to the water current induced by this adduction of

the leg and, as a result, creates the propulsion. At the end of the movement it

reinforces its propulsive action by a powerful extension of the foot. This muscle

is probably the most active in the ankle movement during the phocid swim-

ming. The posterior process of the corpus tali considerably increases the

leverage of the extension of the foot, and hence strengthens this movement

which is essential to phocid swimming. In fact, the flexor hallucis longus of

phocids is better developed than in any other mammals and, as noted by

Howell (1929), its tendon is by far the strongest one of the foot. On land this

characteristic, among others, prevents significant anterior flexion of the foot

and explains why these animals always keep their feet as an extension of the

body. The condition of the phocid talus is unique among mammals and is

considered here as another synapomorphy of the family.

The Phocidae are also defined by an appreciable reduction of the tail,

which, as with the two synapomorphies cited above, is correlated to the

important action of the hind limbs in swimming.

The Phocidae (s.s.) are here divided into two subfamilies: the Phocinae s.s.

and the Monachinae. The subfamily Cystophorinae Simpson, 1945, is no longer

recognized as valid, its taxa having been assigned instead to the Phocinae and

to the Monachinae (King 1966). Although some authors still regard the

Cystophorinae as a monophyletic group (Thenius 1969, 1972), King’s interpre-

tation is followed here.

The Phocinae may be defined by three synapomorphies:

(i) the mastoid crest is curved medially in such a way that it is possible to

observe the mastoid in dorsal view of the skull. This condition is also

found in the monachine Ommatophoca (as noted by Ray 1976a), but in

this genus the crest is straight,

(ii) the carotid foramen is visible ventromedially and not ventrally as in the

Monachinae. This feature is not as constant as (i), but seems to represent

a tendency in the group, and is the consequence of a very strong inflation

of the tympanic bulla,

(iii) the development, on the lateral side of the maxillary, of a well-marked

fossa for the insertion of the caninus muscle. This condition exists only: in

the Phocinae and seems to represent an apomorphy. However, Mirounga,

a monachine, often shows a well-marked caninus fossa. In fact, in this

186 ANNALS OF THE SOUTH AFRICAN MUSEUM

genus the strong development of the caninus seems to be related to the

extreme size of the upper lip, modified into the probicis of the males,

which generally have a deeper caninus fossa than females. The plesiomor-

phic condition seems to be a weak caninus that disappears in most

Monachinae (it has not been observed by Piérard (1971) in Leptonychotes

weddelli); it is strengthened in the Phocinae s.s. and by parallel evolution,

in Mirounga.

The Monachinae are characterized by three synapomorphies:

(i) the premaxilla—maxilla suture is, in its medial part, located inside the nasal

aperture (in Homiphoca capensis it is situated on the nasal aperture

border). In lateral view the visible part of the premaxilla is, therefore,

partially hidden by the maxilla. The plesiomorphic condition is observed in

most of the Phocinae and all the other carnivores where the part of the

premaxilla that is visible laterally is more or less of constant width and

where the premaxilla—maxilla suture is always external to the nasal aper-

ture (Fig. 4),

(ii) there is a tendency for a reduction of the number of upper incisors to four

or two. However, Monotherium? gaudini from the Middle Miocene of the

Abruzze (Italy) is a Monachinae and yet retains six upper incisors (a

plesiomorphic condition),

(iii) there is a clear tendency for the entepicondylar foramen of the humerus

to be lost; this condition is only a tendency because two genera of

Monachinae (Monotherium and Homiphoca) have such a foramen. All the

phocine seals have an entepicondylar foramen which represents a plesio-

morphic condition.

There are other apomorphic tendencies in both subfamilies, mainly in the

postcranial skeleton. For instance, in the monachines, excluding Leptonychotes

weddelli, the deltopectoral crest reaches the distal extremity of the humerus

shaft, while in the phocines it is abruptly interrupted midway along the shaft.

The phocine condition seems to be apomorphic, but Leptonychotes weddelli, a

monachine, shows a similar disposition. Moreover, the humerus of Leptophoca

lenis, a primitive Middle Miocene phocine, shows a condition rather similar to

that in Potamotherium and mustelids. The reduction of the epicondylar crest is

most probably an apomorphic tendency of the monachines, but this feature can

also be found by convergence in Platyphoca vulgaris, a Pliocene phocine. On

the femur the lowering of the trochanter and the reduction of the trochanteric

fossa are also apomorphic tendencies of the monachines, but most of the fossil

and one living (Lobodon carcinophagus) representatives of this group have a

well-marked trochanteric fossa. In other respects, the rotulian facet on the

femur of the monachines shows a clear tendency to become compressed and

more oval and the calcaneum to be more robust in this group than in the

phocines (De Muizon 1981a, tables 8-13); these two features are also regarded

here as apomorphic. However, these apomorphic tendencies, which are not

PHOCID PHYLOGENY AND DISPERSAL 187

C D

Fig. 4. Relationships of the nasal, maxilla and premaxilla in some Phocidae. A. Monachus

tropicalis. B. Leptonychotes weddelli. C. Phoca vitulina. D. Pagophilus groenlandicus.

constant as the three used in Figure 1, were not included in the cladogram.

Nevertheless, circumspectly they can be employed as diagnostic features of

both subfamilies.

THE PHOCINAE S.S.

In view of the scarcity of cranial remains of fossil phocines, only the

phylogeny of living representatives of this group will be considered.

One feature allows the separation of the subfamily into two tribes, Erigna-

thini and Phocini. It is the gluteal fossa on the latteral side of the ilium that is

extremely deep in the Phocini (King 1964; Hendey & Repenning 1972) but is

shallow in the Erignathini and all the monachines. The condition of the Phocini

188 ANNALS OF THE SOUTH AFRICAN MUSEUM

is an apomorphic feature related to the strengthening of hind limb musculature.

No synapomorphy could be found for the Erignathini, a tribe represented at

present by one species only (Erignathus barbatus). It is possible that the study

of fossil phocines, none of which having a deep gluteal fossa, may require a

redefinition of the Erignathini.

The Phocini are known by the living genera Phoca, Pusa, Halichoerus,

Cystophora, Pagophilus, and Histriophoca. Burns & Fay (1970), in a numerical

taxonomic analysis, regarded the genera Phoca, Pusa, Histriophoca and Pago-

philus as subgenera of Phoca. This analysis did not consider either the charac-

ter state (apomorphic or plesiomorphic) or the relative importance of the

features taken into account, and McLaren (1975: 44) already stated the danger

of such a method which ‘. . . may tend to obscure phyletic links’. In the present

study some features assumed to be apomorphic were observed, and this

prompted a division of the Phocini into two groups, namely, the

‘Phoca—Pusa—Halichoerus’ group and the ‘Cystophora—Histriophoca—Pagophi-

lus’ group (Fig. 5).

Phoca—Pusa—Halichoerus

The three genera show a clear tendency toward closing of the external

cochlear foramen by an excrescence of the tympanic bulla external to the

tympanic cavity, and confers a better resistance to water pressure (see p. 193,

Fig. 6). This is considered here as a synapomorphy of this group.

Halichoerus shows the obvious apomorphies of extreme height of the snout

and of the nasal aperture, and a clear tendency towards single-rooted cheek

teeth. Other phocids almost always have double-rooted cheek teeth.

The genera Phoca and Pusa are very similar and some authors (e.g.

Chapskii 1955a; Burns & Fay 1970; Grigorescu 1976; Ray 19766; Repenning et

al. 1979) regard the latter as a subgenus of the former. They differ from

Halichoerus by, among other characters, the more anterior palatine foraminae,

the more reduced premaxillary foraminae, and the larger nasals. These three

characteristics apparently represent apomorphic tendencies in the Phocinae as a

whole and can be regarded as the synapomorphies of Phoca and Pusa. These

two taxa could be referred either to genera (following Scheffer 1958; King

1964; Kirpichnikov 1964) or to subgenera (following Chapskii 1955a; McLaren

1960a; Burns & Fay 1970). However, this subjective difference is here regarded

as being of little significance, and Phoca and Pusa are tentatively listed as sister

genera. This relationship has already been suggested by various authors

(McLaren 1960a; Kirpichnikov 1964; Chapskii 1955a; McLaren 1975).

Phoca pontica, referred by Grigorescu (1976) to the subgenus Pusa, almost

certainly belongs to the Phoca—Pusa group. This conclusion has been accepted

by various authors (Chapskii 19555; McLaren 1960a, 1975; Kirpichnikov 1964;

Repenning et al. 1979). According to Grigorescu, the auditory region of

‘Phoca pontica is very close to that of Pusa, but as no specimen, cast, or

adequate illustrations were available during this study, the characteristic struc-

189

PHOCID PHYLOGENY AND DISPERSAL

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ture of the auditory region of the Phoca—Pusa—Halichoerus group in ‘Phoca’

pontica could not be confirmed. ‘Phoca’ vindoboniensis, whose auditory region

is unknown, was excluded from consideration. The only known specimen of

‘Phoca’ vindoboniensis is the incomplete skeleton lacking the skull described by

Toula (1898). Nevertheless, Grigorescu (1976) has expressed the opinion that it

may probably be related to the Phoca—Pusa group and he concludes that

‘Phoca’ pontica from the Bessarabian deposits (Middle Sarmatian) of the Black

Sea and Caspian Basin is a descendant of ‘Phoca’ vindoboniensis from the

Volhynian deposits (Lower Sarmatian) of the Vienna Basin. Grigorescu’s

interpretation is highly probable but it has still to be confirmed by the discovery

of complete skulls of both species.

Cystophora—Pagophilus—Histriophoca

In these three genera the posterior border of the palate is roughly straight

or forms a very shallow double arch. This feature seems to be fairly constant

for Pagophilus and Cystophora, but Burns & Fay (1970) observed it on only

half of the skulls of Histriophoca that they have examined, the other half

having a distinct notch. This notch, situated in the medial part of the posterior

border of each palatine, is also common in Phoca and Pusa (Burns & Fay

1970), and during the present study it was observed in Monachus, Leptony-

chotes, and Hydrurga. If this notch were absent, the posterior border of the

palate would be roughly straight in Histriophoca and fairly deeply arched in

Phoca and Pusa. Apparently Cystophora, Pagophilus and Histriophoca have a

tendency towards a straight posterior border of the palatine, although it is not

as constant in Histriophoca. This feature is known among the phocids in these

three genera only and for this reason it is interpreted as an apomorphic

condition.

Also in these genera, the mesethmoid extends as far as the posterior

border of the palatines, whereas in the other Phocidae it separates from the

palatines at a point well anterior to it. This feature, which is very probably

related to the preceding one, was observed by Burns & Fay (1970) in only half

of their Histriophoca specimens, while it was constant in all the Cystophora and

Pagophilus specimens examined in the present study. As with the preceding

feature, the Cystophora group shows an obvious tendency for the mesethmoid

to reach the posterior edge of the palate. This condition, which is not found in

other Phocidae, seems to represent a synapomorphy of the group. No satisfac-

tory functional interpretation of these two characteristics could be determined.

In contrast to other Phocinae, the three genera of the Cystophora group

have a well-marked external cochlear foramen (Fig. 6). This is regarded here as

a plesiomorphic condition among the phocids (see p. 195) and therefore it

cannot be used to define the group. In Histriophoca the external cochlear

foramen is located in a conspicuous pit at the limit of the petrosal and of the

mastoid (Burns & Fay 1970). The arrangement is identical in Pagophilus, but in

Cystophora the pit is modified into a groove that separates the mastoid and the

PHOCID PHYLOGENY AND DISPERSAL 191

petrosal. This pit or groove is absent in the other phocines, but the condition

observed in the three genera of the Cystophora group is very similar to that of

Monachus (subfamily Monachinae) and it is regarded as a symplesiomorphy

among the Phocidae (see p. 195).

The resemblances between Histriophoca and Pagophilus are striking but could

represent symplesiomorphies. However, these two genera share an apomorphic

feature: the maxilla—premaxilla suture (in the lateral view of the skull) tends to be

located on the crest of the lateral edge of the nasal aperture (sometimes slightly

inside) (Fig. 4). This feature is a synapomorphy found in the Monachinae (see

p. 193), which is paralleled in Histriophoca and Pagophilus. As with Phoca and

Pusa, Histriophoca and Pagophilus are here regarded as valid genera.

The obvious specializations in Cystophora are:

(i) in the adult male the nasal mucous membrane can be extruded to form a

red ‘bladder’ sometimes as big as the head,

(ii) the posterior extremity of the ascending ramus of the premaxilla is very

low and always at least 2 to 3 cm from the nasal,

(iii) the upper incisors are reduced to four and the lower to two, in contrast to

other phocines that have six upper and four lower incisors.

Discussion

The preceding cladistic analysis of phocines contrasts in some respects with

the relationships suggested by Burns & Fay (1970). They regard Phoca, Pusa,

Histriophoca, and Pagophilus as subgenera of Phoca, thus including the four

taxa in the same group. The interpretation of Burns & Fay is in agreement with

Doutt (1942) who referred the four genera to Phoca but without any subgeneric

division. According to the interpretation presented here, the genus Phoca

(sensu Burns & Fay 1970 and Doutt 1942) is polyphyletic, since Phoca is clearly

related here to Pusa, while Pagophilus is related to Histriophoca. Nevertheless,

if subgenera are to be recognized, then Phoca Linnaeus, 1758, has priority over

Pusa Scopoli, 1777, in the first group, and in the second group Pagophilus

Gray, 1844, has priority over Histriophoca Gill, 1873. Pusa and Histriophoca

would then be relegated to the rank of subgenera.

The Phocini have been divided by Chapskii (1955a) into two subtribes, the

Phocina and the Histriophocina, an arrangement that was followed by King

(1964) and Thenius (1969, 1972). According to these authors, the Phocina

includes the genera Phoca, Pusa, and Halichoerus and the Histriophocina is

made up of the genera Histriophoca and Pagophilus. These subdivisions agree

with the present analysis provided that Cystophora is included in the Histrio-

phocina (King (1966) clearly defined the phocine affinities of this genus).

However, the taxon Histriophocina is not acceptable according to Article 36 of

the International Code of Zoological Nomenclature and Cystophorina Gray,

1837, has priority over Histriophocina Chapskii, 1955. The Phocini could

accordingly be divided into the subtribes Phocina and Cystophorina. This

subdivision is probably pointless and, following the sequencing process of

192 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 6. Right auditory region of some Phocinae showing the auditory foraminae. A. Pagophilus

groendlandicus. B. Cystophora cristata. C. Phoca vitulina. D. Halichoerus grypus. Af—auricu-

lar foramen; ECF—external cochlear foramen; EXB—expansion of the tympanic bulla which

tends to obstruct the external cochlear foramen; EXO—exoccipital; HLI—hyoid ligament

insertion; MAS—mastoid; PTR—petrosal; STM—stylomastoidian foramen; TB—tympanic

bulla. Scale = 3 cm.

PHOCID PHYLOGENY AND DISPERSAL 193

Nelson (1974), the Phocinae are divided here into three tribes: Erignathini,

Phocini, and Cystophorini (Fig. 5).

This interpretation contrasts with that suggested by Arnason (1972) who

stated that some phocids have a 32-chromosomal karyotype while all the others

have 34 chromosomes. He concludes that the 32-chromosomal Phoca, Pusa,

Halichoerus, Histriophoca, and Pagophilus represent a monophyletic group

that excludes the 34-chromosomal Cystophora.

The phocine phylogeny presented here (Fig. 5) is based on living genera

only and will have to be tested as more fossil phocine material is discovered.

THE MONACHINAE

This subfamily is divided into two groups on the basis of an apomorphy in

the auditory region; the tympanic bulla tends to extend backward to cover the

petrosal completely. The plesiomorphic condition among Phocidae is a petrosal

partially visible outside the bulla. The validity of the apomorphy may be

questioned since both Potamotherium and the primitive mustelid Paragale have

a tympanic bulla completely covering the petrosal. Consequently, the plesio-

morphic condition may in fact be apomorphic and vice versa. However, a

functional interpretation justifies the former alternative.

Repenning (1972) pointed out that underwater hearing and pressure resis-

tance are important adaptive factors related to modifications in the auditory

region of seals. Underwater hearing is improved by an increase in the size of

the promontorium (directional audition) and an inflation of the petrosal apex

(auditory sensibility). Another way of improving underwater hearing is the

opening of an external cochlear foramen, which suppresses all bony barriers

between the round window and external environment. Thus, the auditory cells

of the cochlea are separated from the water by flesh only, which creates a

process somewhat similar to the lateral line organ of fishes (Repenning 1972).

In addition, an external exposure of the petrosal, not completely covered by

the bulla, increases the potential and the efficiency of hearing by bony conduc-

tion of the vibrations that are transmitted to the cells of the cochlea directly by

the petrosal. However, the presence of posteriorly exposed petrosal represents

a deficiency in pressure resistance (the pressure resistance is directly connected

to deep diving). In some monachines the increase in pressure resistance is

obtained by a posterior projection of the bulla, which completely covers the

petrosal, and by the development of a mastoid lip overlapping the posterior

wall of the bulla (observed by Repenning & Ray 1977), and which obstructs the

external cochlear foramen.

As noted by Repenning & Ray (1977), Monachus is regarded as the most

primitive of living seals (and even more primitive than most known fossil seals),

and the petrosal of this genus is visible in ventral view of the skull because it is

not completely covered by the tympanic bulla (King 1966). An external

cochlear foramen is also present (Fig. 7). The promontorium and the petrosal

apex are less enlarged than in any other living or known fossil seals (Repenning

194 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 7. Right auditory region of some monachines showing the auditory foraminae. A. Mi-

rounga leonina. B. Monachus monachus. C. Homiphoca capensis. D. Lobodon carcinophagus.

ASF—auriculo-stylomastoid foramen; CF—carotidian foramen; ML—mastoid lip which closes

the external cochlear foramen (For other abbreviations, See Fig. 6.) Scale =3 cm.

PHOCID PHYLOGENY AND DISPERSAL 195

& Ray 1977). Thus, compared with other seals it seems that Monachus is likely

to have poor underwater hearing, improved, however, by the presence of an

external cochlear foramen and by a posteriorly exposed petrosal. These struc-

tures otherwise offer little resistance to high pressure and Monachus is, in fact,

a littoral species and a shallow diver.

Except for some individual variations, the phocine seals have a posteriorly

exposed petrosal and most of them have an opened, or partially opened,

external cochlear foramen. The Phocini show a tendency toward closure of this

foramen, but it is never hermetically obstructed as in some Monachinae. The

phocine petrosal generally has an inflated promontorium and a swollen apex.

Thus, the phocine auditory region is well adapted to underwater hearing

(direction and sensibility), but with rather weak pressure resistance for a seal.

This is in keeping with the fact that phocines are shallow divers (Kooyman &

Andersen 1969; Van den Brink & Barruel 1971).

The condition observed in Monachus is very similar to that in Cystophora.

In both genera the external cochlear foramen is located at the anterior

extremity of a groove separating the mastoid bulla and the petrosal, the latter

not being completely covered by the tympanic bulla. This striking similarity is

here regarded as a symplesiomorphy. There are also slight differences between

the auditory region of both genera. In Monachus the external cochlear foramen

and the groove are always less marked than in Cystophora. In old individuals of

Monachus the external cochlear foramen is sometimes almost obstructed by an

expansion of the bulla. However, in Cystophora the bulla shows a slight

tendency to extend backward and to cover the posterior part of the petrosal,

while in Monachus the external part of the petrosal, at its limit with the bulla,

shows a conspicuous thickening which apparently prevents any posterior

projection of the bulla.

The Antarctic seals are divided into two tribes, the Miroungini trib. nov.

(see p. 199) and the Lobodontini. The Miroungini include (pro parte) the

elephant seals. In this group the bulla completely covers the petrosal but the

external cochlear foramen is wide open, more so than in Monachus. The

promontorium and the petrosal apex are well developed. Consequently, as in

the phocines, the anatomy of the elephant seal indicates good underwater

hearing but a rather poor ability for deep diving when compared with the other

Antarctic seals. In fact, the elephant seals are littoral species and are not

known to be deep divers (Kooyman & Andersen 1969; Bryden 1971).

The living Lobodontini include the four genera: Hydrurga, Lobodon,

Leptonychotes, and Ommatophoca. They have a posterior projection of the

bulla and the external cochlear foramen is completely obstructed by the

development of a mastoid lip overlapping the posterior border of the bulla. The

promontorium is considerably inflated and the apex of the petrosal is very

swollen. Therefore, it seems that the Lobodontini are well adapted for both

underwater hearing (direction and sensibility) and deep diving. Deep diving has

been observed among living Lobodontini in the Weddell seal (Leptonychotes

196 ANNALS OF THE SOUTH AFRICAN MUSEUM

weddelli) that can dive to a depth of 600 m (Kooyman 1966; Kooyman &

Andersen 1969). The greatest diving depth observed for phocine seals is around

300 m and, generally speaking, it is no more than 100 m (Van den Brink &

Barruel 1971).

However, a condition somewhat similar to that of the Lobodontini is

present in Erignathus, a primitive phocine that exhibits some variability in the

structure of its auditory region. In this genus the external cochlear foramen

tends to disappear and the bulla very often covers the petrosal posteriorly.

These two features are never as well marked and constant as in the Lobodon-

tini and a mastoid lip is not present. Erignathus clearly shows the synapomor-

phies of the Phocinae, and the similarities observed sporadically between its

auditory region and that of the Lobodontini are considered here as parallel

apomorphies.

To sum up, the morphological stages representing the modifications of the

auditory region of seals for aquatic adaptation can be illustrated by Potamo-

therium, Monachus, a phocine such as Pagophilus, and a lobodontine such as

Leptonychotes. The auditory region of Potamotherium is already fairly special-

ized, which suggested to Tedford (1976) that this genus is related to the

Phocidae (s.s.). Nevertheless, it also resembles the auditory region of the

primitive mustelid Paragale. In Potamotherium as in otters, but in contrast to

seals, the adaptation to life in water is not pronounced. As in the

Monachus-like stage, early phocids must first have developed underwater

hearing by the shrinking of the tympanic bulla, which exposes the posterior part

of the petrosal underneath, and by the opening of an external cochlear

foramen, which increases the bony transmission of vibrations by the petrosal

and develops a mechanism similar to the lateral line in fish. Such primitive

phocids were evidently shallow divers and must first have increased underwater

hearing rather than pressure resistance. At the Pagophilus-like stage, the

pressure resistance does not show much change, but the underwater hearing is

improved by an inflation of the promontorium and of the petrosal apex. In the

Lobodontini-stage the resistance to pressure is more developed than in any

other seals. It is increased by the posterior projection of the bulla and the

mastoid lip. The extreme development of the promontorium and the petrosal

apex compensate for the obstruction of the external cochlear foramen in the

function of underwater hearing.

It therefore appears that the posterior projection of the tympanic bulla and the

obstruction of the external cochlear foramen represent apomorphies among the

Phocidae. Thus, it is apparently justified to use the first characteristic in a phocid

phylogeny as a synapomorphy of Lobodontini and Miroungini (trib. nov) which

together represent the sister group of the Monachini. The latter group is

characterized by an apomorphic tendency toward oblique implantation of the cheek

teeth relative to the axis of the tooth row, a feature which is always more obvious in

the mandible than in the maxilla (Fig. 8). This feature, also found in some phocines

by convergence, is a consequence of the shortening of the tooth row.

PHOCID PHYLOGENY AND DISPERSAL 197

The Monachini

The living Monachini are represented by one genus and three species,

namely, Monachus monachus, M. tropicalis, and M. schauinslandi, which live

respectively in the Mediterranean and on the Mauritanian coast, in the Carib-

bean, and around Hawaii. The fossil genera of this tribe are Pristiphoca and

Pliophoca. Following Thenius (1950, 1952, 1969, 1972) and contrary to Ray

(1976b), Miophoca Zapfe, 1937, is regarded here as a subgenus of Pristiphoca.

Palmidophoca callirhoe Ginsburg & Janvier, 1975, which is known by only one

cheek tooth, is here regarded as incertae sedis although it may be related to

Pristiphoca, which it closely resembles. Moreover, Paratethyan monachines,

Monotherium? gaudini and Prophoca rousseaui are regarded as incertae sedis

and were not taken into account in this study.

Pristiphoca Gervais, 1859, differs from Monachus in having a more slender

mandible and a longer femur. Two species of this genus are known, P. vetusta

(Zapfe, 1937) from the Middle Miocene of Neudorf (Czechoslovakia), and

P. occitana Gervais, 1859, from the Lower Pliocene of Montpellier (France).

On the mandibles of both species the tooth obliquity is clear, but it is more

marked in the younger species, which is consistent with this being an apomor-

phic character. Thenius (1952: 66, fig. 27) referred a metatarsal III to P. vetusta

which is much longer and hence more specialized than that of Monachus.

Consequently, Pristiphoca is unlikely to be the ancestor of Monachus. The

cheek teeth obliquity is more pronounced and therefore more specialized in

P. occitana and M. monachus than in M. tropicalis arid M. schauinslandi.

However, the three species of Monachus are more similar to each other in

respect of mandible and tooth robustness than to P. occitana. It follows that the

development of oblique cheek teeth relative to the tooth row axis represents a

general tendency of Monachini, having being acquired by parallelism in various

lineages of this tribe. Nevertheless, it is also possible that the palates of

M. tropicalis and M. schauinslandi, which are longer than that of M. monachus

(hence giving more space to the teeth), allow for their readjustment. The

condition of the teeth of the American species would not then be a plesiomor-

phy but a secondary specialization.

Pliophoca etrusca, from the Pliocene of northern Italy, is so similar to M.

monachus that it was initially described by Ugolini (1902) as M. albiventer

(=M. monachus). The material was redescribed by Tavani (1942a) and

assigned to a new genus and species, Pliophoca etrusca. In other respects,

Tavani (1942b) described and illustrated some monachine remains from the

Palaeontological Museum of Florence (Italy). Among these fossils is a talus

that was described and is identical to that of P. etrusca, and one mandible that

fits the skull of the type specimen perfectly. All these specimens are from the

same region and from the same deposits near Orciano and, as noted by Tavani

(1942b), probably belong to P. etrusca. The differences from Monachus .are

slight, with P. etrusca having a more posterior orientation of the proximal

condyle of the humerus, a greater and somewhat higher trochanter of the

ANNALS OF THE SOUTH AFRICAN MUSEUM

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PHOCID PHYLOGENY AND DISPERSAL 199

femur, the femur narrower in its medial part, and the tibia shaft more flattened

anteroposteriorly in its distal third.

The mandible of Pliophoca differs from that of Pristiphoca by its great

stoutness. This feature, which it shares with Monachus, is regarded as a

synapomorphy of Pliophoca and Monachus. The absence of any obvious

characteristic excluding Pliophoca from the ancestry of Monachus and the close

resemblance between the two genera suggests that the Orciano seal is a likely

ancestor of the living monk seals. If this is indeed the case, then the lesser

cheek teeth obliquity in M. tropicalis and M. schauinslandi relative to M. Mon-

achus and P. etrusca represents a secondary specialization (see p. 197). There

is, however, another problem. M. schauinslandi has an obvious plesiomorphy,

that is, the tibia and the fibula of this species are articulated at their proximal

extremities rather than fused as in all the other living seals (Ray 1976b). This

feature may, therefore, exist in P. etrusca, but unfortunately the proximal

extremities of these bones are unknown in the Italian species.

The Miroungini trib. nov.

The tribe is characterized by the posterior projection of the tympanic bulla

and the absence of a mastoid lip closing the external cochlear foramen. It is

represented by one living genus (Mirounga) and one fossil genus (Callophoca).

Palaeophoca nystii van Beneden, 1859, was based on a cetacean tooth and

therefore cannot be a phocid (Ray 1976b). Van Beneden (1887) illustrated

under that name another cetacean tooth and several phocid bones. The latter

should most probably be referred to Callophoca obscura (Ray 1976b).

The only part known of the skull of Callophoca is the auditory region (Ray

1976a, pl. 1, fig. 6). It apparently has no mastoid lip, but differs from that of

Monachus by a clear tendency for the bulla to cover the petrosal posteriorly as

in Mirounga. In this genus the external cochlear foramen differs from that of

Monachus and the Cystophorini. In Mirounga the foramen is wide open and 1s

not partially obstructed by an expansion of the bulla. This contrasts with the

Phocinae in which there is a tendency for it to be closed. In Mirounga there

seems to be a tendency to enlarge the external cochlear foramen but there is no

pit (or groove) separating the mastoid and the petrosal, as observed in the

Cystophorini and Monachus (see p. 191). Moreover, in Mirounga the auricular

foramen, through which the auricular branch of the nerve X passes, very often

joins the stylomastoid foramen to form an auriculostylomastoid foramen. In all

the other seals the auricular foramen is located posteromedially to the stylo-

mastoid foramen. Thus, the characteristics of the auditory region of Mirounga

differ from those of Monachus and the Cystophorini. The tendency for enlarge-

ment of the external cochlear foramen apparently represents an apomorphy of

Mirounga.

Since the skull of only one member of the tribe is known (Mirounga) the

recognition of synapomorphies characterizing the group is difficult. The apo-

morphies of Mirounga could be at generic rather than tribal level. However,

200 ANNALS OF THE SOUTH AFRICAN MUSEUM

Ray (1976b) observed a feature (apparently apomorphic) that would seem to

indicate a close relationship between Mirounga and Callophoca. This latter

genus is represented in Europe (Belgium) and in North America (U.S.A.) by

two species, C. obscura and C. (= Mesotaria) ambigua. The latter is much

larger than the former, but they are otherwise very similar, and Ray (1976b)

suggests that this difference could be reasonably explained by sexual dimorph-

ism. Since Mirounga is the only living phocid that exhibits marked sexual

dimorphism, this could represent an amomorphy characterizing the Miroungini.

The suggested relationship of Callophoca to Mirounga was also made on

the basis of striking similarities between the femora and humeri of both genera,

although the apomorphy of these features is not demonstrated. These bones of

the two genera are similar to those of Monachus, although they differ from this

genus in the following respects:

(i) the humeri of Callophoca and Mirounga are more twisted in lateral view,

they have a more proximally orientated condyle, a longer deltoid crest and

a better developed epicondylian ridge,

(ii) the femora of Callophoca and Mirounga have a more globular proximal

condyle, a lower trochanter and a wider distal extremity.

There are no known features that contradict the hypothesis that Callo-

phoca is ancestral to Mirounga.

A provisional diagnosis of Miroungini trib. nov. is: Monachinae, character-

ized by marked sexual dimorphism and in which the auditopy region shows a

posterior projection of the tympanic bulla but without a mastoid lip obstructing

the external cochlear foramen as observed in Lobodontini.

The Lobodontini

This group is distinguished by a posterior projection of the tympanic bulla

and a mastoid lip. The living representatives can be divided into two groups

(Hendey 1972; De Muizon & Hendey 1980). They are:

1. The Ommatophoca—Leptonychotes group, which is characterized by the

following apomorphic features:

(i) flattening of the skull,

(ii) shortening of the snout,

(iii) reduction of the cheek teeth and of their accessory cusps.

The only known representatives of this group are the living genera Omma-

tophoca and Leptonychotes.

2. The Lobodon—Hydrurga group, which have the following synapomor-

phies:

(i) relatively high skull,

(ii) lengthening of the snout,

(iii) relatively large cheek teeth, with an emphasis in the size and number of

the accessory cusps,

PHOCID PHYLOGENY AND DISPERSAL 201

(iv) postero-internal projection of the cingulum of the upper cheek teeth, on

which a well-defined postero-internal cusp is almost always developed.

This group is composed of two living genera, Lobodon and Hydrurga, and

four known fossil genera, Monotherium, Homiphoca, Acrophoca, and Pisco-

Dhoca.

The genus Monotherium, usually regarded as an ancestral form of the

living monk seals, is here referred to the Lobodontini. This is based on the fact

that Monotherium? wymani has a posterior projection of the bulla and a

mastoid lip (Ray 1976a). As already stated concerning Piscophoca pacifica (De

Muizon 19815), all the similarities between Monotherium and Monachus are

most probably to be considered as symplesiomorphies. Although the characters

of the Lobodon—Hydrurga group could not be observed in Monotherium, the

close relationship of this genus to Piscophoca pacifica (De Muizon 1981b)

suggests that Monotherium belongs to this group.

Homiphoca was suggested by De Muizon & Hendey (1980) to be on the

lineage leading to Lobodon on the basis of the following supposed synapomor-

phies:

(i) the relatively wide interzygomatic bridge of the frontal,

(ii) the appreciable height of the M,,

(iii) the tendency for the presence of numerous accessory cusps strongly

recurved towards the main cusps.

This relationship between Homiphoca and Lobodon was suggested

because there are no obvious characteristics that preclude this hypothesis, while

they share some common features that can be regarded as apomorphic.

Acrophoca is distinguished by the extreme length and tapering of its snout.

In this respect it is more specialized than Lobodon and Hydrurga and cannot be

directly ancestral to either genus. It does, however, have two apomorphic

characters in common with Hydrurga that separate them from the other

Lobodontini. They are:

(i) the considerable length of the temporal fossa,

(ii) the sagittal crest that is more developed than in any other monachine.

Thus, Acrophoca could represent a branch from the Hydrurga lineage.

Piscophoca pacifica is apparently a descendant of Monotherium (De Mui-

zon 1981b). These two seals share a feature unique among the known phocids,

that is, the posterior border of the proximal extremity of the humerus shaft has

a very deep fossa where the triceps brachii (caput mediale) is partially inserted.

Of the two species of Monotherium whose humerii are known, M. aberratum is

the most likely ancestor for Piscophoca pacifica. This interpretation confirms

the assignment of Monotherium to the Lobodontini and to the Lobodon-

Hydrurga group.

Satisfactory apomorphic features to link the lineages Homiphoca-Lobo-

don, Acrophoca—Hydrurga and Monotherium—Piscophoca were not found and

there are therefore three possibilities that can be considered.

202 ANNALS OF THE SOUTH AFRICAN MUSEUM

Discussion

Repenning et al. (1979) have suggested a phocid phylogeny based upon

biogeographic groups, but without precise information about the genera

included in each branch. The phocines are divided into two groups: the

Atlantic-Arctic group and the Paratethyan group. However, the genus Pusa

(considered by the authors as a subgenus of Phoca) is very likely a descendant

of the Paratethyan seals (such as ‘Phoca’ pontica or ‘Phoca’ panonica). It was

also concluded earlier that Pusa is closely related to Phoca, both genera being,

at least partially, Atlantic—-Arctic seals (see p. 188). Consequently, the relation-

ships of those two groups are much more complex and their phylogenetic

homogeneity is not established. Moreover, the Paratethyan seals have not all

been proved to be phocines and ‘Monotherium’ maeoticum may well be a

monachine.

Repenning et al. (1979) divide the monachines into a Hawaiian group, a

Caribbean—Atlantic group and an Antarctic group. Once again, viewed in

relation to the phocid phylogeny suggested here, these biogeographic groups

are very heterogeneous. For example, the Caribbean—Atlantic group includes

such genera as Monotherium and Callophoca (which are clearly related to the

Antarctic seals), and Monachus and Pliophoca, the latter obviously related to

the monk seals. This group, therefore includes representatives of the three

tribes of Monachinae defined here. The Hawaiian Islands group, which includes

the living species Monachus schauinslandi, is defined merely by geographic

isolation, associated with the persistence of plesiomorphic features in M.

schauinslandi such as the articulated tibia and fibula and the primitive morph-

ology of the petrosal (Repenning & Ray 1977). In fact, one synapomorphy of

both the Caribbean—Atlantic group and the Antarctic group could separate the

Hawaiian Islands group, that is, the presence in the former two of a tibia and

fibula fused at their proximal extremity. It can, therefore, be argued that the

Hawaiian monk seal does not belong to the genus Monachus but must be

assigned to a new genus. This is not advocated because that synapomorphy is a

feature that can be ascribed to convergence. For example, Repenning &

Tedford (1977) record an Otariidae (Thalassoleon) whose tibia and fibula are

articulated, whereas all the living otariids have fused tibiae and fibulae. This

feature is also found in some Xenarthra and reflects a strengthening of the limb

for vigorous use.

A phylogeny based upon assumed apomorphic features is here preferred to

one based on geographic groupings.

PHOCID PALAEOBIOGEOGRAPHY

McLaren (1960a), Hendey (1972), Thenius (1972), Ray (1976a), and

Repenning ef al. (1979) have discussed phocid palaeobiogeography, but some

points concerning monachine dispersal are re-examined in the light of the

phylogeny presented here.

PHOCID PHYLOGENY AND DISPERSAL 203

NORTHERN ORIGIN OF MONACHINES

The authors cited above consider that the origin of all phocids, including

the monachines, was in the North Atlantic, where most of the known fossil

representatives of this family are found. The northern monachines are from at

least four fossil genera, namely, Monotherium, Callophoca, Pristiphoca, and

Pliophoca. Monotherium is recorded from the Middle and Upper Miocene of

North America and the Upper Miocene of Belgium. Callophoca is from the

Pliocene of Virginia (U.S.A.) and of Belgium. Pliophoca (Pliocene) and

Pristiphoca (Middle Miocene and Lower Pliocene) are European genera. The

following points support the theory of the northern origin of monachines:

(i) Monotherium aberratum, which is found on the eastern coast of U.S.A.,

seems the most likely ancestor of Piscophoca pacifica. This implies a

southern migration of this lineage,

(ii) Callophoca, a northern genus (U.S.A., Belgium), is the likely ancestor of

Mirounga, which is represented at least partially in the southern hemi-

sphere: M. leonina lives in the Antarctic waters, while M. angustirostris

breeds along the Californian coast.

MODE OF DISPERSAL

Hendey (1972: 103 fig. 1) suggests a dispersal of the monachines along the

transatlantic and coastal currents. It is highly probable that currents did play an

important role in the migrations of marine mammals such as phocids. Neverthe-

less, it seems unlikely that the coastal currents were significant because the

phocids are very dependent on the land and their dispersal along the coasts

might have been independent of the direction of the currents. The situation in

respect of transatlantic currents is very different. It is most unlikely that seals

could have crossed the Atlantic swimming against the current, and it follows

that these currents played a prominent part in the dispersal of the monachines

(De Muizon & Hendey 1980).

ORIGIN AND DISPERSAL ROUTES OF MONACHINE TRIBES.

The Monachini

All the living and fossil representatives of this tribe are located in warm

waters and in low latitudes.

The presence of monk seals (Monachus) in the Mediterranean (M. mona-

chus), in the Caribbean (M. tropicalis), and around Hawaii (M. schauinslandi)

indicates at least one crossing of the Atlantic by this group. The apparent

preference of the Monachini for warm waters makes it highly probable that the

crossing was in the southern North Atlantic, by way of equatorial currents from

east to west. It follows that the original homeland of the Monachini must have

been in Europe.

Several factors support this hypothesis. Firstly, the three described species

of fossil Monachini are from southern Europe, while the Yorktown Formation

204 ANNALS OF THE SOUTH AFRICAN MUSEUM

in the south-eastern United States, where the phocid remains are very abun-

dant, is apparently devoid of Monachini. In addition, if this group originated in

North America, their crossing of the Atlantic could have been accomplished

only by a ‘palaeo-Gulf Stream’ which would have carried them towards nor-

thern Europe. However, no Monachini are known in the Antwerp sands

(Belgium), and seals of the ‘faluns de la Touraine et de Anjou’ (Ginsburg &

Janvier 1971, 1975) have yet to be established as Monachini because they are

known only by isolated teeth.

The most probable migration route for the Monachini would, therefore,

have been southward following the north African coast (Mauritania and Sene-

gal) and crossing the Atlantic by way of the equatorial currents to reach the

coast of Brazil and continuing north to the Caribbean. It is possible, therefore,

that the common ancestor of the living species of Monachus that gave rise to

M. monachus in the Mediterranean migrated eastward by this route, giving rise

in the Caribbean to the ancestors of the living M. tropicalis and M. schauins-

landi. It is worth noting that these two species are closer to each other than

either is to M. monachus (King 1956; Scheffer 1958). M. schauinslandi, or its

ancestors, would then have passed into the Pacific Ocean before the emergence

of the Panama Isthmus, about 3,5 to 4 m.y. ago (see Beggren & Hollister

1974). The Phocidae might have been the last marine animals to cross this route

because of their ability to move on dry land.

An undescribed monachine from Sud-Sacaco (Peru), which is known only

by mandibles and some postcranial bones, has characteristics that suggest it

belongs to the Monachini. Because of the slenderness of its mandible, it is

closer to Pristiphoca than to Monachus and its size is similar to that of P.

vetusta. As in that species, the metapodials are proportionally longer than those

of Monachus; the Sud-Sacaco Monachini cannot, therefore, be ancestral to any

of the living monk seals. In addition, it must have entered the Pacific Ocean

before 4 or 5 m.y. ago, the assumed age of the Sud-Sacaco fauna (De Muizon

& Bellon 1980). Therefore, there could have been two migrations from east to

west, the first one giving rise to the Monachini of Sud-Sacaco, and the second

to M. tropicalis and M. schauinslandi.

The assumed Monachinae of the Paratethys, such as ‘Monotherium’ mae-

oticum Nordman, 1860, and ‘Phoca’ bessarabica Simionescu, 1925, are possibly

Monachini, but because they are so poorly known they are listed here as

incertae sedis (table 1).

Ray (1976b) and Repenning et al. (1979) have proposed the idea that

Monachus re-invaded the Mediterrenean from the Atlantic after the Messinian

crisis. In fact, the complete desiccation of the Mediterranean is now seriously

questioned and the main defendants of this idea (Hst et al. 1973) have had to

moderate their interpretation in face of the strong opposition of several

geologists and palaeontologists working on the Mediterranean littoral. Many

authors now regard the idea of a complete desiccation of the Mediterranean

basin as somewhat extremist and simplistic (Montenat 1977; Gaudant 1978;

PHOCID PHYLOGENY AND DISPERSAL

TABLE 1

Phocid classification.

Cystophorini

Undetermined

tribe —

Family Subfamily

PHOCINAE

PHOCIDAE Incertae sedis

Monachini

MONACHINAE _ | Miroungini

Lobodontini

*Fossil genera and species

205

Genera and species

Erignathus

Phoca

Pusa

Halichoerus

Cystophora

Pagophilus

Histriophoca

Phocanella*

Platyphoca*

Leptophoca*

Gryphoca*

‘Phoca’ vindoboniensis*

‘Phoca’ pontica*

Prophoca rousseaui*

‘Monotherium’ meoticum*

‘Monotherium’ gaudini*

‘Phoca’ bessarabica*

Pliophoca*

Pristiphoca*

Monachus

Callophoca*

Mirounga

Monotherium*

Homiphoca*

Acrophoca*

Piscophoca*

Lobodon

Hydrurga

Leptonychotes

Ommatophoca

Busson 1979; Sorbini & Tirapelle Rancan 1979; Roep & Van Harten 1979,

Rouchy 1979; Montenat et al. 1980). It seems highly probable that even during

the most critical period of the Messinian event some lakes and lagoons, at least,

persisted on the periphery of the Mediterranean; this does not contradict the

possibility of a complete desiccation in some basins of the Mediterranean.

Hence, it seems quite possible and more satisfactory to consider that the

pre-Messinian Monachini never disappeared from the Mediterranean, giving

rise there to Pliophoca and Monachus during the Pliocene.

206 ANNALS OF THE SOUTH AFRICAN MUSEUM

The Miroungini

The living Miroungini occur in Subantarctic waters (Mirounga leonina) and

on the Californian coast (M. angustirostris), while the fossil representatives of

this tribe, Callophoca obscura and C. ambigua, which are very probably

conspecific, have been found in Europe (Belgium) and North America (east

coast of U.S.A.). The European origin of this tribe cannot be substantiated.

The presence of Callophoca in northern Europe and the fact that it was not

found in southern Europe suggest a crossing of the Atlantic Ocean by way of

the northern North Atlantic. The Gulf Stream, which crosses the Atlantic in

that zone, flows from west to east and it is therefore possible that Callophoca

crossed the Atlantic Ocean in this direction. On the other hand, Repenning et

al. (1979) have expressed the opinion that the primitive monachines were

probably warm-water animals like the living monk seals and that the adaptation

to Arctic and Antarctic conditions is a recent development among the phocids.

This observation suggests a migration via the southern North Atlantic by way of

the equatorial currents from east to west. Both migration routes are thus

possible.

Since Callophoca is the likely ancestor of Mirounga, it is possible that the

former entered the Pacific Ocean during the Early Pliocene to give rise here to

the Mirounga lineage, with M. angustirostris in the north and M. leonina in the

south. The latter species, which is now rare on the Pacific coast of South

America, was common there two centuries ago, the type locality of the species

being Juan Fernandez Islands (Chile) where they have since been exterminated

(Scheffer 1958).

The Lobodontini

As with the Miroungini, the original homeland of the Lobodontini is

uncertain. In the Northern Hemisphere, Lobodontini have been found in the

Upper Miocene of Belgium: they are Monotherium aberratum, M. delognii and

M. affine (very probably conspecific with M. delognii, see Ray 1976b and De

Muizon 1980a). In northern Italy, Guiscardi (1871-3) described Phoca gaudini

from the Miocene of the Abbruzes. This species was referred to Monotherium

by Sarra (1930), Ginsburg & Janvier (1975), and Ray (19766). The cheek teeth

of M.? gaudini are not obliquely implanted as they are in the Monachini, which

suggests that it does not belong to this group. However, the auditory region

that is necessary to recognize a Lobodontini is not known and, following Ray’s

(1976b) opinion, this species is here regarded as incertae sedis. In North

America, Monotherium? wymani comes from the Calvert Formation (Middle

Miocene from Virginia, U.S.A.) and M. aberratum is known in the Gay Head

Green Sand of St Marys Formation (Late Miocene from Maryland, U.S.A.).

There are two possible centres of origin for the Lobodontini, namely,

Europe and North America. In the case of the former, the North Atlantic

would have been crossed in the south by way of equatorial currents (east to

west), whereas in the case of a North American origin, the crossing would have

PHOCID PHYLOGENY AND DISPERSAL 207

fon Southern limit of the Phocinae

=== Recent distribution of the Monachini

(from Ray 1976)

Recent distribution of the Miroungini

Recent distribution of the Lobodontini i NG ZG Ta 0e to a ‘ soe GaGa

*: iN POI) OR Camis 1 mod ie Of

Sal)

.

ih Stnemtamemeeenmaae nein! Sot inate eee

5 Hane

ih

Fig. 9. Distribution of recent Monachinae and probable ways of dispersal of the monachines.

MN—fossil Monachini; MR—fossil Miroungini; LB—fossil Lobodontini.

1. Migration of the Monachini (and probably all the Monachinae) by way of equatorial

currents.

2. Possible west to east migration for the Miroungini and the Lobodontini (in the case of a

North American origin for these two tribes).

3. Migration of the Monachini to Hawaiian Islands (Monachus schauinslandi).

4. Settlement of the Miroungini on the Californian coast (Mirounga angustirostris).

5. Southward migration of the Lobodontini that settled on the Peruvian coast in the Upper

Miocene—Lower Pliocene. Probable southward migration of the Miroungini.

6. Probable ways of migration of the Lobodontini in the South Atlantic.

7. Possible migration of Argentinian monachines to South Africa by way of the Antarctic

current.

8. Establishment of the Lobodontini in Antarctic waters.

(N.B. See Addendum.)

208 ANNALS OF THE SOUTH AFRICAN MUSEUM

been by way of the Gulf Stream (west to east) in the northern North Atlantic.

Lobodontini entered the Pacific before 4 to 5 m.y. ago and are represented on

the Peruvian coast in the Lower Pliocene (Sud-Sacaco). It is also possible that

the Lobodontini migrated along the Atlantic coast of South America to

Argentina (assuming that the monachine teeth described by Frenguelli (1922)

are in fact Lobodontini) and from there, crossing the South Atlantic by way of

the west-to-east Antarctic current, settled in South Africa where thay are

represented by Homiphoca capensis (Hendey 1972).

However, a study of undescribed monachine material from the Middle

Miocene of Argentina (De Muizon & Bond 1982), clearly states that no

close relation exists between Homiphoca capensis and the Argentinian pho-

cid. The latter belongs to a different lineage and probably must be classified

in the Monachini; however, this is not proved, and no skull of the Argentin-

ian form is known. Considering this relationship, the authors stated that a

monachine migration from the Argentinian coast to South Africa is very

improbable and suggested that the ancestor of Homiphoca might have

migrated southward along the Atlantic coast of Africa. This was also stated

by De Muizon (1982).

To sum up, the migration southward of the Lobodontini is certain only on

the Pacific coast of South America. In the Atlantic Ocean it might have been

along the African or South American coast, or both. Repenning et al. (1979,

fig. 2) suggest that the only southward migration for the Lobodontini was along

the Pacific coast of South America. As stated by De Muizon (1981c) it seems

highly improbable that this group of North Atlantic origin would not have used

the South Atlantic in its migration to the Antarctic.

CONCLUSIONS

The Phocidae originated in the Northern Hemisphere. The phocine seals

established themselves in the North Atlantic Ocean and spread to the Pacific,

crossing the Arctic Ocean probably during the Pleistocene (Ray 19766), while

the monachines migrated southward. The Monachini stayed in warm subtropi-

cal and tropical waters, while the Lobodontini and Miroungini (except. for

M. angustirostris) reached Antarctic waters during the Pliocene. The original

homeland of the Phocidae is rather difficult to determine because of the poor

fossil record of early forms, but indications are that it was in Europe.

Phocid remains are fairly abundant in Europe (Paratethys and Antwerp

Basin) and in North America (Virginian and Carolinian coasts). The oldest

known fossil phocids are about 15 m.y. old (Middle Miocene) and are known in

Rurope and North America; Potamotherium (Semantoridae) comes from Early

and Middle Miocene levels of Europe. The Phocidae, therefore, most probably

appeared during the Oligocene. During this period, central Europe was a

complex mosaic of intracontinental basins, an environment favourable for the

acquisition of the aquatic adaptations. Moreover, the Semantoridae (Potamoth-

erlum and Semantor) are apparently exclusively from Europe and western Asia,

PHOCID PHYLOGENY AND DISPERSAL 209

the American evidence for these genera being very doubtful. A European

origin for the Phocidae is far from being proven, but it is in accord with the

known fossil record of the family and would satisfactorily explain many prob-

lems of phocid palaeontology. For example, the phocine features of the

? monachines of the Paratethys can be explained as plesiomorphic features

common to the Phocinae and Monachinae and these monachines could, there-

fore, stem from a very primitive monachine lineage, geographically close to the

centre of dispersal of the Phocidae. Thus, from the centre of Europe during the

Oligocene, the first phocids would have reached the North Sea and the place of

the future Paratethys and the Mediterranean. The Paratethys appears at the

Early Miocene with the closure of the Ouralian, Trans-Polish, and Alsatian

Straits, which separated it from the Boreal seas (Pomerol 1973). Later, two

phocid populations were isolated and evolved separately in the North Sea and

in the Mediterranean—Paratethys.

Phocinae and Monachinae were most probably present in both regions

during the Miocene. This would seem to indicate that, before the separation of

the two geographical areas during the Early Miocene, the subfamilies of

Phocidae were already differentiated. In the case of the monachines, this

geographical separation would have given rise in the north to the Miroungini

and Lobodontini and in the south to the less specialized Monachini. This

hypothesis has to be tested by the discovery of more complete material in

southern Europe. During the Early Miocene the northern population of

European phocids might have migrated to the Americas by way of the

European west coast and the equatorial currents of the Brazilian coast. They

would then have colonized the Caribbean and the eastern seaboard of North

America. As noted by Repenning et al. (1979), the Miocene phocids were

apparently adapted to relatively warm water conditions and this makes an

equatorial crossing of the North Atlantic more likely. Moreover, a northern

crossing of the North Atlantic would imply that they might have swum against

the Gulf Stream, which, as stated previously, is improbable. In the Caribbean

and on the coast of North Carolina and Virginia, the monachines apparently

prospered, whereas the phocines were much less abundant (Repenning ef al.

1979). During the Miocene and the Pliocene, the southern population of

European monachines apparently followed the same route to reach the Ameri-

cas (see p. 204). The Lobodontini and the Miroungini then passed into the

Pacific and migrated to the south along the Pacific coast of South America, but

the Atlantic coasts of South America and Africa were also very probable routes

of southward migration for these monachines (p. 208). Most of the Monachini

and all the Phocinae remained in the Northern Hemisphere.

This interpretation of phocid dispersal is rather speculative, for example, it

is not demonstrated that all the monachines of southern Europe are Monachini.

Nevertheless, considering the scarcity of fossil phocid material it is thought, as

does Hendey (1972), that it is preferable to speculate a little than to wait for

hypothetical new discoveries.

210 ANNALS OF THE SOUTH AFRICAN MUSEUM

Unclassifiable specimens are common in the fossil phocid record; most of

the specimens are isolated bones or fragments with very few skull elements.

Even when the remains are almost complete (e.g. Piscophoca pacifica, Acro-

phoca longirostris, Pliophoca etrusca, Homiphoca capensis), the phylogenetic

relationships may still be difficult to determine. Consequently, all hypotheses

on the phylogeny and dispersal of the Phocidae could be radically changed by

new discoveries of well-preserved material from critical areas. This was clearly

indicated by Ray (1976b: 404).

ADDENDUM

This paper was already prepared when Schmidt-Kittler (1981) published his interpretation

of musteloid and procyonoid relationships. In the latter work Potamotherium is excluded from

the Musteloidea (sensu Tedford 1976) and regarded as a form close to the procyonids without

any precise relationship being defined. Nevertheless, the affinities of Potamotherium indicated

in the present paper are confirmed elsewhere (De Muizon in press) by some anatomical

evidence mainly in the auditory region.

In Figure 9 the Argentinian monachines are regarded as Lobodontini. In a study present-

ing some new monachine material from Argentina, De Muizon & Bond (1982) stated that these

phocids should very probably be related to the Monachini; unfortunately this information came

too late to allow the modification of Figure 9. The authors also stated that, considering this

interpretation, a monachine migration from Argentina to South Africa was highly improbable

(see p. 208).

ACKNOWLEDGEMENTS

The help of Dr Q. B. Hendey of the South African Museum concerning

the form and content of the manuscript is gratefully acknowledged. I thank

J. Crapart for the drawings and J. Chalavoux for the photographs.

This study was undertaken under the auspices of the Institut Frangais

d’Etudes Andines of Lima (Peru) and of the Institut de Paléontologie of Paris

(France).

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6. SYSTEMATIC papers must conform to the Jnternational code of zoological nomenclature

(particularly 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.

Nnov., 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 transferred 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 speci-

mens 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, description 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 Elizabeth (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 _

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

(c) Scientific names, but not their vernacular derivatives

e.g. Therocephalia, but therocephalian

Punctuation should be loose, omitting all not strictly necessary

Reference to the author should 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 alcne, but be preceded by the generic name or its abbreviation

to initial capital letter, provided the same generic name is used consecutively. :

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.

SMITHSONIAN INSTITUTION LIBRARIES

SNOT

3 9088 01206 6825

CH. DE MUIZON

PHOCID PHYLOGENY

AND DISPERSAL