European Journal of Taxonomy 76: 1-18

http://dx.doi.org/10.5852/ejt.2014.76

WWW, europeanj ournaloftaxonomv. eu

2014 • Okanishi M. & Fujita T.

ISSN 2118-9773

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Research article

um:lsid:zoobank.org:pub:01BEFFB2-2E53-4BlE-A7BC-36702313BBF8

A taxonomic review of the gtvms Asterostegus (Echinodermata:

Ophiuroidea), with the description of a new species

Masanori OKANISHr-^ * & Toshihiko FUJITA^'*

^ Seto Marine Biologieal Eaboratory, Field Seienee Edueation and Researeh Center, Kyoto University,

459 Shirahama, Nishimuro, Wakayama, 649-2211 Japan

^National Museum of Nature and Seienee, 4-1-1 Amakubo, Tsukuba, Ibaraki, 305-0005 Japan

* Corresponding author. E-mail: [email protected]

^ um:lsid:zoobank.org:author:6F730D3A-A6FC-41FD-B5F6-9629D55E4547

^ urn:lsid:zoobank.org:author:D5B6C696-9E5B-4012-A9A9-4716DD2BA2C3

Abstract. A revision of the genus Asterostegus Mortensen, 1933 (Eehinodermata: Ophiuroidea:

Euryalidae) is based on seven speeimens, ineluding the holotype of Asterostegus maini MeKnight,

2003. A new speeies, Asterostegus sabineae sp. nov., is deseribed from off Reunion Island and two

other speeies, A. tuberculatus Mortensen, 1933 andU. maini, are redeseribed. A tabular key to the three

speeies of the genus Asterostegus is provided. Some terminology of the taxonomy of euryalid ophiuroids

is revised.

Keywords. Taxonomy, brittle stars, Asterostegus sabineae, new speeies, Indo-Westem Paeifie.

Okanishi M. & Fujita T. 2014. A taxonomic review of the gQwm Asterostegus (Echinodermata: Ophiuroidea), with

the description of a new species. European Journal of Taxonomy 76: 1-18. http://dx.doi.org/10.5852/ejt.2014.76

Introduction

The family Euryalidae Gray, 1840 is widely distributed in the Indo-West Paeifie (Kroh 2004). The genus

Asterostegus (Ophiuroidea: Euryalida: Euryalidae) was ereeted by Mortensen (1933b) monotypieally

fox Asterostegus tuberculatus Mortensen, 1933 and is eurrently eomposed of A. tuberculatus Moxtmsm,

1933 and A. maini MeKnight, 2003. The genus is morphologieally related to the genus Astroceras

(Euryalidae), but is elearly distinguished by having oral interradial plates (Mortensen 1933b; MeKnight

2003).

The monophyly of this genus is eonfirmed by a reeent moleeular phylogenetie study (Okanishi & Fujita

2013), but taxonomie works ox\. Asterostegus speeies are searee. Asterostegus tuberculatus was originally

deseribed by Mortensen (1933b) based only on the holotype, but a seeond speeimen was reeorded by

Clark & Courtman-Stoek (1976). Asterostegus maini was also originally deseribed by MeKnight (2003),

based only on the holotype. MeKnight (2003) distinguished the aforementioned two speeies ehiefiy

by the arrangement and size of tubereles on the radial shields and lateral bars, and by the arrangement

of plates on the oral interradius. However, these deseriptions laeked quantitative aeeounts of sizes of

the tubereles (Mortensen 1933b; Clark & Courtman-Stoek 1976; MeKnight 2003), making it diffieult

European Journal of Taxonomy 76 : 1-18 ( 2014 )

to distinguish the two species of Asterostegus as well as to compare newly collected specimens of

Asterostegus.

In the present study, Asterostegus maini and A. tuberculatus are redescribed based on the holotype of

A. maini and one newly collected specimen of A. tuberculatus. A new species of Asterostegus is based

on five specimens collected from off Madagascar. In recent descriptions of ophiuroids, photographs

and/or drawings of each part of the body, as well as SEM images of each ossicle, provide valuable

taxonomic information (e.g., Okanishi & Fujita 2009; Okanishi & Fujita 2011a, 2011b; Okanishi &

Fujita 2014; Martynov 2010). To date, drawings and photographs of A. tuberculatus and A. maini have

been presented of limited parts of the body (Mortensen 1933b; McKnight 2003) only. Herein we present

detailed photographs of many parts of the body and SEM images of separated ossicles.

30°

50°S

Asterostegus tuberculatus

□ Asterostegus maini

o Asterostegus sabineae sp. nov.

180°E

10°30'S

irso's

30°E 35° 40° 45° 50° 55° 60° 165°30'E 166°

166°30'

167°

Fig. 1. Known distribution of Asterostegus maini McKnight, 2003, A. sabineae sp. nov., and A. tuber¬

culatus Mortensen, 1933 are indicated by square, circle and star shaped symbols respectively. Solid

symbols indicate the type locality of each species.

OKANISHIM. & FUJITA T., A taxonomic review of the genus Asterostegus

Material and methods

The seven speeimens used in this study are deposited in the National Institute of Water and Atmospherie

Researeh (NIWA), Museum National d’Histoire Naturelle (MNHN) and the Swedish Museum of Natural

History (SMNH).

The holotype (MNHN MO-01) and four paratypes of the new speeies were fixed in 99% ethanol (SMNH-

Type-8333; SMNH-Type-8536). One non-type speeimen of A. tuberculatus (SMNH-123461) was fixed

in 99% ethanol. The fixation method of the holotype of A. maini (NIWA 7564, H-733) is unknown.

Ossieles of one paratype of the new speeies (SMNH-Type-8536) and of A. tuberculatus (SMNH-I2346I)

were isolated by immersion in domestie bleaeh (approximately 5% sodium hypoehlorite solution),

washed in deionized water, dried in air, and mounted on SEM stubs using double-sided eonduetive tape.

The preparations were sputter-eoated with gold-palladium and examined with a HITACHI S-4300 SEM

at the Seto Marine Biologieal Eaboratory (Kyoto University). Apart of the mouth frame, aboral shields,

and oral interradial plates of one paratype of the new speeies (SMNH-Type-8536) and A. tuberculatus

were exposed by dissolving skin with domestie bleaeh.

The terms used to deseribe ophiuroids follow Stohr et al. (2012) and Okanishi et al. (2013). Familial

level systematies follow Okanishi & Fujita (2013).

The number and arrangement of plate-shaped ossieles on the distal side of the adoral shields (Figs

2H, 6F, 7F-G) is an important eharaeter for the elassifieation of Asterostegus. They were deseribed as

“interradial plates” by Mortensen (1933b: 297) and as “ventral interradial plates” by MeKnight (2003:

389). MeKnight’s “ventral interradial plates” is a relatively unambiguous deseription beeause it elearly

indieates the position of the plate. However, “ventral” is not usually used for ossieles on the oral frame.

Here, we suggest that the ossieles should all be referred to as “oral interradial plates”. Bar-shaped

ossieles on the aboral and lateral side of arms are also an important taxonomie eharaeter (Fig. 71). These

ossieles were deseribed by Mortensen (1933b: 298) as “lateral bars” and by MeKnight (2003: 389) as

“dorsolateral plate”. The “dorsolateral plates” is a term easily eonfiised with the “lateral arm plates”

of ophiuroids. We propose the use of “lateral bars” in this study. The lateral bars are present on the

proximal portion of the arms of Asterostegus. A pair of bars eovers the lateral and aboral side of eaeh

arm segment and earry tubereles on their aboral surfaee.

Results

Superfamily Euryalidea Gray, 1840

Family Euryalidae Gray, 1840

Genus Asterostegus Mortensen, 1933

Asterostegus yioriQwson, 1933a: 4, 40; 1933b: 297.

Asterostegus -f^ q\\ 1960: 10. —MeKnight 2003: 385-386.

Type speeies: Asterostegus tuberculatus Mortensen, 1933, by monotypy.

Diagnosis

Arms simple, not branehing. Tubereles present on radial shields and aboral arms. Oral interradial plates

present on distal side of adoral shields. Teeth triangular. Oral papillae domed, granule-shaped, present

laterally on the jaws. Tentaele pores with two (rarely three) arm spines from fourth arm segment. Oral

side of vertebrae with an oral bridge. Eamina of distal arm spines smooth.

European Journal of Taxonomy 76 : 1-18 ( 2014 )

Table 1. A tabular character key to the species of Asterostegus.

Numbers and

arrangement of

oralinterradial

plates

A. sabineae

sp. nov.

Two to four, in a line on the

radial shield

One or two

ca. 1-1.2 mm

One in each

interradius

A. maini

McKnight, 2003

Ca. 10, only on periphery

of radial shield

Three to five

ca. 250-300 pm

Three to five

arranged in one row

A. tuberculatus

Mortensen, 1933

Scattered over entire radial

shield and peripheral part

of aboral disc

Two or three

ca. 350 pm

Five to eight

arranged in two

rows

Tubercles on aboral surface of the disc

Species

Number and arrangement

of tubercles on aboral disc

Number of

tubercles on top of

each lateral bar

Length of tubercles

on periphery of

radial shields

Remarks

Based on this study, Asterostegus is currently composed of three species, A. sabineae sp. nov., A. maini

McKnight, 2003 and A. tuberculatus Mortensen, 1933. A tabular key to the species of Asterostegus is

provided (Table 1).

Species of this genus are distributed in the Indian Ocean, off Madagascar (Mortensen 1933b) and in the

Western Pacific, south-east of New Caledonia (McKnight 2003), at a depth of 382-500 m (Fig. 1).

Asterostegus sabineae sp. nov.

um:lsid:zoobank.org:act:D2F3C5E4-B56D-4726-A7B7-FDB56A85B95F

Figs 2-5

Asterostegus sp. - Okanishi & Fujita 2013: 568, 575, fig. 1, table 1.

Diagnosis

Tubercles ca. 1-1.2 mm long cover entire radial shields. On proximal portion of arm, one (rarely two)

tubercle on each lateral bar. One oral interradial plate present on each interradius.

Etymology

The specific name is for Dr. Sabine Stohr of the Swedish Museum of Natural History, eminent Swedish

researcher of the Ophiuroidea.

Type material

MADAGASCAR: Holotype (MNHN lE-2013-8012), three paratypes (SMNH-Type-8333) and one

paratype (SMNH-Type-85436), all ethanol preserved specimens, off Madagascar, South Cape, Sainte

Marie, 26°16.35’S, 45° 10.45’E, 409-473 m, 14 May 2010, collected during the cruise Atimo Vatae 2010,

St. CP3616.

Description

Measurements. Holotype (MNHN lE-2013-8012): disc diameter 11.7 mm, arm length 118 mm. One

paratype (SMNH-Type-8536): disc diameter 13.3 mm, arm length at least 55.4 mm (arms convoluted).

OKANISHIM. & FUJITA T., A taxonomic review of the genus Asterostegus

Fig. 2. Asterostegus sabineae sp. nov., holotype (MNHN IE-2013-8012) and one paratype (SMNH-

Type-8536) (H). A. Aboral dise and proximal portion of arms. B. Aboral periphery of dise. C. Aboral

eentral dise. D. Oral dise and proximal portion of arms. E. Jaws. F. Oral periphery of dise and proximal

portion of arm. G. Lateral dise. H. Lateral dise, skin removed to observe internal ossieles, an arrow

indieates the madreporite; aboral proximal portion of arm. Abbreviations: ADS = adoral shield, AS =

Arm spine, GEO = granule-shaped external ossieles. Go = gonads, GS= genital slit, OIP= oral interradial

plate, Te = teeth, TS = tentaele sheath, Tu = tuberele.

European Journal of Taxonomy 76 : 1-18 ( 2014 )

Disc. Disc circular m shape. Radial shields and their surrounds tumid (Fig. 2A). Aboral surfaee of dise

eovered by skin and two to four domed tubereles in a line on eaeh radial shield (Fig. 2A-C). Tubereles ca.

1.0-1.2 mm long on dise periphery, ca. 0.8 mm long at dise eenter (Fig. 2B). Radial shields, ca. 7.5 mm

Fig. 3. Asterostegus sabineae sp. nov., holotype (MNHN lE-2013-8012) (A-F). A. Aboral basal portion

of arm. B. Aboral middle portion of arm. C. Aboral and lateral distal portion of arm. D. Oral proximal

portion of arm. E. Oral middle portion of arm. F. Lateral distal portion of arm. Abbreviations: AS = arm

spine, LAP = lateral arm plate. Ten = tentaeles, Tu = tuberele.

OKANISHIM. & FUJITA T., A taxonomic review of the genus Asterostegus

long, 0.7-2.7 mm wide, eompletely eovered by skin and tubereles (Fig. 2B-C). Oral surfaee of dise

eovered by skin (Fig. 2D-E). More than three triangular teeth form vertieal row on dental plate (Fig. 2E).

One oral interradial plate present on distal side of adoral shield (Fig. 2H). Eateral interradial surfaee of

dise nearly vertieal, eovered by skin and granule-shaped external ossieles, ca. 150-400 pm long (Fig.

2H). Two genital slits in eaeh interradius, 3.0 mm long and 0.4 mm wide (Fig. 2H). One madreporite

present on distal side of oral interradial plate (Fig. 2H).

Fig. 4. Asterostegus sabineae sp. nov., paratype (SMNH-Type-8536), SEMphotographs. A-D. Vertebrae

from middle portion of arm: distal view (A), aboral view (B), oral view (C), lateral view (D). E-H.

Vertebrae from distal portion of arm: distal view (E), aboral view (F), oral view (G), lateral view (H). I.

Eateral arm plate from middle portion of arm. Abbreviations: K = knobs, MO = musele opening, OB =

oral bridge.

European Journal of Taxonomy 76 : 1-18 ( 2014 )

Arms. Arms simple, five in number, with no abrupt gap in width due to presenee of gonads in proximal

portion of arms (Figs 2A; 3A). Arms tapering gradually distally. Proximal portion of arms 3.0 mm wide

and 3.7 mm high, oblong in eross-seetion. Aboral surfaee arehed and oral surfaee fiattened from middle

to distal portion of arms. Proximal portion of the arms eovered by skin and one (rarely two) domed

tubereles, ca. 1.0-1.3 mm long (Fig. 3A), on eaeh lateral bar. If two tubereles present on lateral bar,

both are smaller, ca. 800 pm long (Fig. 3A). From middle to distal portion of arms, tubereles gradually

deerease in size distally, beeoming absent near arm tips (Fig. 3B-C). Oral surfaee of arms eovered by

skin (Fig. 3D-E). First to third tentaele pores laeking arm spines; two arm spines from fourth pore (Fig.

2F). In proximal third of arms, outer arm spines ca. one quarter to half as long as eorresponding arm

segment, and inner arm spines slightly shorter than outer spines (Figs 2F; 3D). In middle of arms inner

and outer arm spines subequal, ca. two-thirds as long as eorresponding arm segment (Fig. 3D). In distal

third of arms, arm spines hook-shaped (Fig. 3F). Inner and outer spines subequal, ca. two-thirds as long

Fig. S.Asterostegus sabineae sp. nov., paratype (SMNH-Type-8536), SEM photographs. A. Eateral arm

plate from middle portion of arm, abradial view. B. Eateral arm plate from distal portion of arm, adradial

view. C. Eateral arm plate from distal portion of arm, oral view. D-F. Arm spines: from proximal portion

of arm (D), middle portion of arm (E), distal portion of arm, an are indieates lamina (F). Abbreviations:

MO = musele opening, NO = nerve opening, ST = seeondary tooth.

OKANISHIM. & FUJITA T., A taxonomic review of the genus Asterostegus

as eorresponding arm segment (Fig. 3C, E-F). Lateral arm plates eoneealed by skin and visible at distal

arm tips where skin beeomes thinner (Fig. 3E).

Colour. Body ereamy white, arm spines brown (Figs 2A, G, H; 3B, D). Colour in life is unknown.

Ossicle morphology. Ossieles separated from one paratype, SMNH-Type-8536. Vertebrae. Vertebrae

with streptospondylous artieulations (Fig. 4A, E), oral bridges on oral side (Fig. 4C, G) and knobs on

lateral side (Fig. 4D, H), and not inelining from proximal-aboral side to distal-oral side of arms (Fig.

4B, D, F, H) throughout the arms. These features indieate the new speeies’ affiliation to the family

Euryalidae. Knobs on proximal portion of arms elongated, beeoming rounded toward distal portion of

arms (Fig. 4D, H).

Lateral arm plates. Lateral arm plates in middle portion of arms with two pairs of musele and nerve

openings, eaeh of them assoeiated with arm spine artieulation (Figs 41, 5A-C). Dorsal and ventral lobes

beside musele openings eontaet eaeh other, a tuberele strueture present between eaeh musele and nerve

opening (Figs 41, 5 A). Arm spines elub-shaped, both 650 pm long and wide on proximal portion of arms

(Fig. 5D), 450 pm long and 500 pm wide on middle portion of arms (Fig. 5E), hook-shaped, ca. 230 pm

long on distal portion of arms, with one seeondary tooth and smooth lamina on proximal portion (Fig.

5F).

Distribution

Only known from off Madagasear, 409-473 m depth (type loeality, present study).

Remarks

The new speeies falls within Asterostegus by virtue of having simple arms, tubereles on radial shields

and aboral arms, oral interradial plates, triangular teeth and granule-shaped oral papillae, an oral bridge

on oral side of vertebrae, and smooth lamina of distal arm spines (Fell 1960; MeKnight 2003).

Asterostegus sabineae sp. nov. ean be distinguished from the other two speeies as follows: two to four

tubereles on the radial shields of the present new speeies form a line on eaeh radial shield (Fig. 2A),

whereas the tubereles of A. maini number ca. 10 and are seattered on the periphery of the radial shields

only (Fig. 6C). Those of A. tuberculatus number 5-15 and are seattered over the entire radial shields as

well as on the interradial areas and periphery of the aboral dise (Fig. 7A). The size of tubereles of the

new speeies on the periphery of the radial shield is ca. 1.0-1.2 mm long (Fig. 2B). In eontrast, those of

A. maini and A. tuberculatus in the same position are ca. 250-300 pm (Fig. 6C) and ca. 350 pm long

(Fig. 7A), respeetively.

The new speeies has one or two tubereles on the top of eaeh lateral bar in the arms proximally (Fig.

2H), whiled, maini and A. tuberculatus have three to five (Fig. 6H), and two to three tubereles (Fig. 71),

respeetively.

The number of oral interradial plates of the new speeies is one on eaeh interradius (Fig. 3F) while

there are three to five plates in A. maini (MeKnight 2003) and five to eight in A. tuberculatus (Fig.

7G) (Mortensen 1933b). The oral interradial plates of the latter two speeies form rows (see also the

deseription of A. tuberculatus) (MeKnight 2003).

Asterostegus maini MeKnight, 2003

Fig. 6

Astroceras elegans MeKnight, 1989: 25 {non Astroceras elegans Bell, 1917).

Asterostegus maini MeKnight, 2003: 386-389, figs 1, 2 (replaeement name).

European Journal of Taxonomy 76 : 1-18 ( 2014 )

Asterostegus maini - Okanshi & Fujita 2013: 568, 571, 575, fig. 1, tables 2-3.

Diagnosis

About 10 tubercles present on periphery of radial shields, ca. 250-300 pm long. On proximal portion

of arm, three to five tubercles on top of each lateral bar. Three to five oral interradial plates forming one

row.

Type material

Holotype (NIWA 7564, H-733), ethanol preserved specimen, vicinity of Pukapuka Atoll, Manihiki

Plateau, Cook Islands, New Zealand, 10°53.0’S, 165°55.2’W - 10°52.4’S, 165°55.4’W, 417-446 m

depth, 21 Apr. 1986.

Description

Measurements. NIWA 7564, H-733: disc diameter 22 mm, arm length at least 205 mm (arms convoluted).

Disc. Disc circular in shape with notched interradial margins (Fig. 6A-B). On aboral surface, radial

shields and their surrounds tumid (Fig. 6A, C). Aboral surface of the disc covered by skin and club-

shaped tubercles on periphery of radial shields, ca. 250-300 pm (Fig. 6C). Radial shields, ca. 10.0 mm

long and F7-2.1 mm wide, and completely covered by skin (Fig. 6D). Oral surface of the disc covered

by skin (Fig. 6E). Seven to eight spear head-shaped teeth forming a vertical row on dental plate (Fig.

6E). Domed and granule-shaped oral papillae lying on each side of jaw, but can not be seen when wet

(Fig. 6E). Two or three oral interradial plates form a row on proximal side of adoral shields but cannot

be seen clearly when wet (Fig. 6F). The oral interradial plates projecting from lateral side of the disc

(Fig. 6G). Eateral interradial surface of the disc nearly vertical, covered entirely by skin (Fig. 6G). Two

genital slits in each interradius, E6 mm long and 0.2 mm wide (Fig. 6G).

Arms. Arms simple, five in number, with no abrupt gap in width due to presence of gonads in proximal

portion of arms. Arms tapering gradually distally. Proximal portion of the arms 6.7 mm wide and 7.1

mm high, oblong in cross-section. Aboral surface arched and oral surface fiattened from middle to distal

portion of arms. Proximal portion of the arms covered by skin and three or four (rarely five) club-shaped

tubercles, ca. 170-340 pm long, on each lateral bar (Fig. 6H). Tubercles gradually decrease in size and

number distally, becoming absent near arm tips (Fig. 61). Entire oral surface of arms covered by skin (Fig.

6J). First to third tentacle pores lacking arm spines; fourth pore with two (rarely one or three) arm spines

(Fig. 6J). All arm spines on each tentacle pore subequal throughout arms (Fig. 6J, K). In proximal third

of arms, arm spines ovoid and minute (Fig. 6J), ca. one-third to two-thirds as long as corresponding arm

segment (Fig. 6J). In middle of arms, arm spines club-shaped, as long as corresponding arm segment. In

distal third of arms, arm spines hook-shaped, as long as corresponding arm segment (Fig. 6K). Eateral

arm plates concealed by skin.

CoEOUR. McKnight (2003) described the colour of the holotype as “In ethanol, areas between radial

shields as well as dorsal surfaces of arms light brown, rest of body creamy-white”. However, by our

observation, the holotype is uniformly creamy white. The colour might be diluted in long term ethanol

preservation. Colour in life is unknown.

Distribution

Only known from off Cook island, 417-446 m depth. New Zealand (type locality, McKnight 2003).

OKANISHIM. & FUJITA T., A taxonomic review of the genus Asterostegus

Fig. 6. Asterostegus maini MeKnight, 2003 (NIWA 7564, H-733). A. Aboral view. B. Oral view.

C. Aboral periphery of dise. D. Aboral eentral dise. E. Jaws. F. Oral periphery of dise. G. Lateral dise.

H. Aboral proximal portion of arm. I. Aboral middle portion of arm. J. Oral proximal portion of arm.

K. Lateral middle portion of arm. Arrows indieate positions where oral interradial plates should exist (F,

G). Abbreviations: ADS = adoral shield, AS = arm spine, GS = genital slit, LAP = lateral arm plate, Te

= teeth. Ten = tentaele, Tu = tuberele.

European Journal of Taxonomy 76: 1-18 (2014)

Remarks

Asterostegus maini is related to A. tuberculatus in sharing relatively small tubereles and multiple oral

interradial plates on eaeh interradius, while A. sabineae possess relatively large tubereles and only one

oral interradial plate.

Asterostegus maini and A. tuberculatus ean be distinguished by the size and arrangement of tubereles

on the dise, the number of tubereles on lateral bars, and the number and arrangement of oral interradial

plates (Table 1, see also remarks for^. sabineae).

Asterostegus tuberculatus Mortensen, 1933

Figs 7-10

Asterostegus tuberculatus Mortensen, 1933: 298-300, figs 24-25, pi. 19; figs 4-5.

Asterostegus tuberculatus - Okanishi & Fujita 2013: 568, 572, 575, fig. 1, tables 2-3.

Diagnosis

Tubereles present on periphery of radial shields as well as interradial periphery of dise, ca. 350 pm long.

On proximal portion of arm, two or three tubereles on top of eaeh lateral bar. Five to eight oral interradial

plates forming two rows.

Material examined

SMNH-123461, one ethanol preserved speeimen, west eoast of Reunion Island, 500 m, 2009.

Description

Measurements. SMNH-123461: dise diameter 14.5 mm, arm length 259 mm.

Disc. Dise eireular in shape, with notehed interradial edges (Fig. 7A). On aboral surfaee, radial shields

and their surrounds tumid (Fig. 7A). Dise surfaee eovered by skin and evenly seattered tubereles (Fig.

7A-C). Tubereles on dise eenter granule-shaped, ca. 300 pm diameter and 400 pm height (Fig. 7C)

and on periphery elub-shaped tubereles, ca. 350 pm diameter and 550 pm height (Fig. 7B). Radial

shields, ca. 1.5 mm long and 0.7-2.0 mm wide (Fig. 7A), eompletely eovered by skin and tubereles.

Oral surfaee of the dise eovered by skin and granule-shaped external ossieles, ca. 120-240 pm diameter,

whieh are evenly seattered (Fig. 7D, F). Four spearhead-shaped teeth form a vertieal row on dental plate

(Fig. 7E). Six to seven domed oral papillae lie on eaeh side of jaw (Fig. 7E). Adoral shields somewhat

hexagonal-shaped (Fig. 7F). Oral interradial plates pentagonal or hexagonal-shaped, in two rows (Fig.

7G). Proximal row eonsists of two oral interradial plates, distal row eonsists of three interradial plates

(Fig. 7G). Eateral interradial surfaee of dise nearly vertieal, eovered entirely by skin (Fig. 7H). Two

genital slits in eaeh interradius, 4.1 mm long and 0.7 mm wide (Fig. 7H). One madreporite present

between oral side of genital slits (Fig. 7H).

Arms. Arms simple, five in number, with no abrupt gap in width due to presenee of gonads in proximal

portion of arms. Arms tapering gradually distally. Proximal portion of arms 6.85 mm wide and 5.5 mm

high, oblong in eross-seetion. Aboral surfaee arehed and oral surfaee fiattened from middle to distal

portion of arms. Proximal portion of arms eovered by skin and two or three elub-shaped tubereles,

ca. 400 pm long and 750 pm height (Figs 71; 8J-K), on eaeh lateral bar. On middle portion of arms,

tubereles granule-shaped, ca. 450 pm long (Fig. 9A), one or two on eaeh lateral bar. On oral surfaee,

four to five granule-shaped external ossieles, seattered on eaeh arm segment, ca. 150-300 pm long on

proximal portion of arms (Fig. 9C) and ca. 100-150 pm long on middle portion of the arms (Fig. 9D).

Tubereles and external ossieles on oral surfaee gradually deerease in size distally, beeoming absent near

OKANISHIM. & FUJITA T., A taxonomic review of the genus Asterostegus

Fig. 7. Asterostegus tuberculatus Mortensen, 1933 (SMNH 123461). A. Aboral dise and proximal

portion of arm. B. Aboral periphery of dise. C. Aboral eentral dise. D. Oral dise. E. Jaws. F. Oral

periphery of dise. G. Oral periphery of dise, skin removed to observe internal ossieles, oral interradial

plates of the same row are eonneeted by blaek bars. H. Lateral dise, an arrow indieates madreporite. I.

Aboral proximal portion of arm. Abbreviations: ADS = adoral shield, GEO = granule-shaped external

ossiele, GS = genital slit, LB = lateral bar, OIP = oral interradial plate, OP = oral papillae, Te = teeth.

Ten = tentaele, Tu = tuberele.

European Journal of Taxonomy 76: 1-18 (2014)

100 um

100 jjmllOO pm

100 um

100 pm

Fig. 8. Asterostegus tuberculatus Mortensen, 1933 (SMNH 123461), SEM photographs. A-C. Lateral

arm plates from middle portion of arm: internal view (A), oral view (B) and external view (C). D-F.

Late-ral arm plates from distal portion of arm: external view (D), internal view (E) and oral view (F).

G-I. Arm spines from proximal portion (G), middle portion (H) and distal portion, an are indieates lamina

(1). J-K. Tubereles on proximal portion of arm: external view (J) and lateral view (K). Abbreviations:

MO = musele opening, NO = nerve opening, ST = seeondary tooth.

OKANISHIM. & FUJITA T., A taxonomic review of the genus Asterostegus

arm tips (Fig. 9B, E-F). First to third tentaele pores laeking arm spines; two arm spines from fourth pore

(Fig. 7D). In proximal third of arms, arm spines ovoid and minute (Figs 8G; 9C). Outer arm spines ca.

two-thirds as long as eorresponding arm segment, inner arm spines slightly shorter, ca. two-thirds as

long as outer spine (Fig. 9C). In middle of arm, arm spines elub-shaped (Figs 8H; 9D). Inner and outer

arm spines of equal length, ca. half as long as eorresponding arm segment (Fig. 9D). In distal third of

arms, arm spines hook-shaped with smooth lamina on distal side (Fig. 9E). Inner and outer spines of

equal length, ca. one-third as long as eorresponding arm segment (Figs 81; 9E-F). Eateral arm plates

eoneealed by skin and external ossieles, with two pairs of musele and nerve openings, and eaeh of them

assoeiated with an arm spine artieulation (Fig. 8A-F). Ventral lobes and dorsal lobes beside musele

openings meet (Fig. 8C-D). A eondyle present between eaeh musele and eaeh nerve opening (Fig. 8C,

Fig. 9. Asterostegus tuberculatus Mortensen, 1933 (SMNH 123461). A. Aboral middle portion of arm.

B. Aboral distal portion of arm. C. Oral proximal portion of arm. D. Oral middle portion of arm. E. Oral

distal portion of arm. F. Eateral distal portion of arm. Abbreviations: AS = arm spine, EAP = lateral arm

plate, Tu = tuberele.

European Journal of Taxonomy 76: 1-18 (2014)

Fig. Asterostegus tuberculatus MoxiQWSQn, 1933 (SMNH 123461), SEM photographs. A-D. Vertebra

from middle portion of arm: distal view (A), aboral view (B), oral view (C) and lateral view (D). E-H.

Vertebrae from distal portion of arm: distal view (E), aboral view (F), oral view (G) and lateral view (H).

Abbreviations: K = knob, OB = oral bridge.

OKANISHIM. & FUJITA T., A taxonomic review of the genus Asterostegus

D). Vertebrae with streptospondylous artieulations (Fig. lOA, E), oral bridges on oral side (Fig. lOA, C,

E, G), knobs on lateral side (Fig. lOB, D, F, H). These features indieate A. tuberculatus' affiliation to the

family Euryalidae. Knobs on lateral side of vertebrae elongate throughout the arms (Fig. lOB, D, F, H).

Colour. Uniformly white, slightly grayish on aboral dise surfaee exeept radial shields (Fig. 7A). Blaek

spots appear on aboral and lateral arms randomly, every 2-20 arm segments (Fig. 71). Colour in life is

unknown.

Distribution

Off Durban, 376 m depth, Republie of South Afriea (type loeality, Mortensen 1933b). Off Reunion

Island, 500 m depth (present study).

Remarks

Asterostegus tuberculatus ean be distinguished from the other two speeies in the arrangement of tubereles

on the dise, numbers of tubereles on lateral bars, and the arrangement of oral interradial plates (Table 1,

see also the Remarks for the other two speeies).

Acknowledgements

We are most grateful to Sadie Mills (NIWA) for her eritieal reading of the manuseript and eonstruetive

eomments. We wish to express our sineere gratitude to Owen Anderson and Kareen Sehnabel (NIWA)

for their assistanee with the examination of the holotype of Asterostegus maini and to Sabine Stohr

(SMNH) for arranging the loans of examined speeimens. This work was supported by grants from the

Researeh Institute of Marine Invertebrates (Tokyo), the Showa Seitoku Memorial Foundation, and the

Japan Soeiety for the Promotion of Soeiety (Seientifie Researeh [C] No. 22570104, Researeh fellowships

for Young Seientists No. 22506).

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Manuscript received: 25 November 2013

Manuscript accepted: 6 January 2012

Published on: 6 March 2014

Topic editor: Rudy Jocque

Desk editor: Kristiaan Hoedemakers

Printed versions of all papers are also deposited in the libraries of the institutes that are members of

the EJT consortium: Museum National d’Histoire Naturelle, Paris, France; National Botanic Garden

of Belgium, Meise, Belgium; Royal Museum for Central Africa, Tervuren, Belgium; Natural History

Museum, Eondon, United Kingdom; Royal Belgian Institute of Natural Sciences, Brussels, Belgium;

Natural History Museum of Denmark, Copenhagen, Denmark.