Gorgonocephalus pectinatus Mortensen, 1933

O’Hara, Timothy D. & Thuy, Ben, 2025, Seamount ophiuroids from the High Seas of the western Indian Ocean, Zootaxa 5718 (1), pp. 1-88 : 18-20

Gorgonocephalus pectinatus Mortensen, 1933

Fig. 5a – c, o – t

Gorgonocephalus pectinatus Mortensen, 1933b: 281 – 285 , fig. 16 – 17, pl. 18(1 – 2).

Gorgonocephalus pectinatus . — Clark, A.M. & Courtman-Stock, 1976: 133, fig. 86, 88.

Gorgonocephalus pustulatum . — Baker, 1980: 54 – 56, fig. 18b, 20, 30 (in part). — Olbers et al. 2019: 70 – 72, fig. 48 – 49 [Non Gorgonocephalus pustulatum (Clark H L, 1916) ].

? Gorgonocephalus pustulatum . — Calero & Ramil, 2023: 67 – 68, figs 10 – 11.

STUDY MATERIAL. — JC066 : stn 8-22, Atlantis Bank, 32° 42.225´S, 57° 18.02´E to 32° 42.59´S, 57° 17.01´E, 1000 m, 13/12/2011: 1 ( NHMUK 2025.31 ) ( DNA code= JC066-3749 ) .

COMPARATIVE MATERIAL EXAMINED. Gorgonocephalus dolichodactylus Döderlein, 1911 :TAN0308/90, Lord Howe plateau, 34° 12.17´S, 163° 21.36´E to 34° 12.617´S, 163° 16.783´E, 1090 – 1117 m, 26/5/2003 , MV F99711 ( DNA code= F99711 ). TAN1206/3, Site SL 1a, slope, Bay of Plenty , 37° 10.158´S, 176° 39.522´E to 176° 39.762´N, 37° 9.96´W, 681 – 710 m, 15/4/2012 , MV F188859 ( DNA code=02W2H). Gorgonocephalus pectinatus Mortensen, 1933b :AFR246/ A28872 , 35° 8´S, 23° 9´E, 451 m, 11/9/2008 , SAMC MB-A88409 ( DNA code=A88409). Gorgonocephalus pustulatum (H.L. Clark, 1916) : IN2018 _ V06 /178, St Helens Seamount, 41° 13.584´S, 148° 45.72´E to 41° 13.536´S, 148° 45.72´E, 727 – 755 m, 16/12/2018 , MV F271944 ( DNA code=F271944). TN228/ RD1, 2008 , MV F242193 ( DNA code=F242193). Gorgonocephalus sundanus Döderlein, 1927 : SS05/2007/107, Northwestern Australia, Leveque L 27 transect, 14° 49.026´S, 121° 27.552´E to 14° 48.533´S, 121° 29.567´E, 400.5- 378.2 m, 27/6/2007 , MV F162682 ( DNA code=F162682) .

Distribution. South Africa ( 78 – 580 m),?E Atlantic ( 902 – 908 m), Atlantis Seamount ( 1000 m).

Remarks. Gorgonocephalus forms 2 clades on our phylogeny, the subantarctic-boreal G. chilensis-eucnemis and the temperate-tropical G. pustulatum-dolichodactylus-sundanus clades. Both Gorgonocephalus clades occur on the SW Indian Ocean Ridge. Two specimens found on the southern Coral seamount fall into the G. chilensis clade and another from the more northern Atlantis Seamount into the G. pustulatum clade. They differ in the placement of girdle hooklets (which continue across the dorsal arm by the first arm branching in G. pustulatum and start at the 2nd fork in G. chilensis ) and the greater tuberculation along the arms in chilensis ( Baker 1980) .

Within the G. pustulatum clade, the Atlantis specimen ( 38 mm dd) clusters with a specimen from South Africa (A88409), and both specimens are polyphyletic with respect to Australian-New Zealand G. pustulatum specimens (being separated by specimens of G. dolichodactylus , which lack a secondary tooth on girdle hooklets). Consequently, like for Astrothorax , we reject the trans-Indian Ocean synonymy of Baker (1980), recognise the SW Indian Ocean population as a separate allopatric species and resurrect the name G. pectinatus for this species. Calero & Ramil (2023) report a specimen of G. pustulatum from off Guinea-Bissau in the tropical eastern Atlantic. No DNA sequences are available; and it is unclear whether this represents a new lineage or a range extension of G. pectinatus .

The LAPs ( Fig. 5g, p ) differ slightly between G. chilensis and G. pectinatus , the muscle opening on the arm spine articulations is more slit-like in G. chilensis (similar to the Arctic G. eucnemis , see Martynov 2010a, pl. 1(2)) and the rim is less elevated than in G. pectinatus . More data from other species is required to see if this is diagnostic for the two clades discussed above. The hooklet base plates on the lateral side of the arm ( Fig. 5i, r ) are largely similar, both species having the hemispherical or rhomboid-shaped hooklet articulation surface and asymmetrical tubercle foramen that allow the hooklets to function as pedicellariae ( Turner et al. 2021).

Figures

FIGURE 5. (a–c) Gorgonocephalus pectinatus NHMUK 2025.31 (a) dorsal disc, (b) dorsal (whole animal), (c) lateral arm; (d–n) Gorgonocephalus chilensis NHMUK 2025.30 (d) dorsal disc, (e) dorsal (whole animal), (f) lateral arm, (g) lateral arm plate, exterior view, (h) lateral arm plate, interior view, (i) lateral arm hooklet plate, (j) dorsal arm hooklet plate, (k) distal arm spine, (l) proximal arm spine; (m) vertebra of proximal segment, distal view, (n) vertebra of distal arm segment, distal view; (o–t) Gorgonocephalus pectinatus NHMUK 2025.31 (o) vertebra, distal view, last segment before branching, (p) lateral arm plate, exterior view), (q) lateral arm plate, interior view, (r) arm hooklet plate, (s) hooklet, (t) proximal arm spine.