Gordonopsis ceto, Ng & Forges, 2020

Ng, Peter K. L. & Forges, Bertrand Richer de, 2020, A revision of the deep-sea porter crabs of the genus Gordonopsis Guinot & Richer de Forges, 1995 (Crustacea, Decapoda, Brachyura, Homolidae), with descriptions of five new species, Raffles Bulletin of Zoology 68, pp. 267-307 : 292-299

Gordonopsis ceto , new species

( Figs. 24–26 )

Material examined. Holotype: female (9.3 × 13.6 mm) (NTOU), station CST 12, Horse Shoe Ridge, hard bottom without mud, with many white dead bivalves and one Bathymodiolus shell, many soft corals and squat lobsters, 22°0.953′N, 118°53.955′E – 22°4.864′N, 118°52.785′E, 758–1,346 m, South China Sea, Taiwan, coll. T.-Y. Chan, 29 April 2016.

Diagnosis. Female: carapace longitudinally ovate, width to length ratio 0.68, distinctly wider posteriorly than anteriorly; dorsal carapace surface with well-defined regions, separated by broad, deep grooves; lateral margin convex; dorsal parts with scattered soft setae that do not obscure surface; lateral parts with setae that do not obscure surface ( Figs. 24 A–C, 25A, B). Rostrum long, sharp, with 2 long, obliquely directed pseudorostral spines, just shorter than rostrum ( Fig. 24A ). Supraorbital margin relatively narrow, C-shaped; pseudorostral spines directed obliquely laterally at angle of about 45° ( Fig. 24A ). Eyes with short ocular peduncle, cornea prominent; no discernible orbit ( Fig. 24A ). Hepatic region gently inflated, with short obliquely directed spine ( Fig. 24A ). Gastric region without spines ( Fig. 24A ). Gastric groove well marked, with distinct ovate gastric fossae just above ( Fig. 24A ). Cardiac region swollen; branchial region inflated, with distinct branchio-cardiac grooves ( Fig. 24A ). Latero-posterior tubercle on carapace low, just discernible as granule ( Fig. 24A ). Base of antenna with distinct spine ( Fig. 25D ). Antennal flagellum short, second and third articles thick, setose. Epistome triangular ( Fig. 25D ). Third maxilliped pediform, merus elongate with angular external angle ( Fig. 25C ). Chelipeds long; fingers long, greater than half length of palm; surface gently rugose with scattered small granules; carpus longitudinally ovate, outer margin with 2 or 3 long spines, distal edge with 1 long spine, inner margin with 1 long spine, sometimes with additional spinule, dorsal surface with longitudinal row of 2 or 3 spinules; merus triangular in cross-section, relatively long, curved, dorsal margin with 7 spines and distal 2 spines bracketing chela, outer ventral margin with 7 spines, inner ventral margin with 3–5 spinules ( Fig. 25 E–H). Ambulatory legs very long; basis-ischium with 4 spines on each margin; P2 merus with 3 spines on dorsal margin (excluding 1 distal spine), ventral margin with 1 or 2 spinules or sharp granules; P3 merus with 2 spines on dorsal margin (excluding 1 distal spine), ventral margin with 1 spinule; P4 merus with 1 spine on dorsal margin (excluding 1 distal spine), ventral margin unarmed, outer surface smooth, without trace of spinule or granule ( Figs. 24A , 26A , E–G). P5 merus slender, unarmed on all margins, reaching beyond gastric groove when folded anteriorly; carpus long, propodus short, enlarged, forming prominent pseudochela with stout, gently curved dactylus; occlusal margin of fixed finger with 8 spines, that of dactylus with 7 or 8 spines ( Fig. 26H, I ). Outer margin of P2 coxa with 1 short, stout spine on proximal edge, outer margin of P4 coxa with 1 or 2 short, stout spines on each edge ( Fig. 26 B–D). Proximal part of telson subtrapezoidal, with distal half triangular ( Fig. 26B ).

Colour. In life, the carapace is greyish-brown, and the chelipeds and ambulatory legs are orange ( Fig. 30B ).

Etymology. The species is named after Ceto, a Greek sea goddess, sister and wife of Phorcys. The name is used as a noun.

Remarks. See general discussion for comparisons with congeners.

Figures

Fig. 24. Gordonopsis ceto, new species, holotype female (9.3 × 13.6 mm) (NTOU), South China Sea. A, overall habitus; B, dorsal view of carapace; C, dorso-frontal view of carapace.

Fig. 25. Gordonopsis ceto, new species, holotype female (9.3 × 13.6 mm) (NTOU), South China Sea. A, lateral view of cephalothorax; B, frontal view of cephalothorax; C, left third maxilliped; D, ventral view showing buccal cavity, epistome, antennae, and antennules; E, outer view of merus and carpus of right cheliped; F, outer view of right carpus and chela; G, dorsal view of left cheliped; H, dorsal view of right cheliped.

Fig. 26. Gordonopsis ceto, new species, holotype female (9.3 × 13.6 mm) (NTOU), South China Sea. A, dorsal view of carapace showing relative P5 length; B, ventral view of cephalothorax showing coxae, basis-ischia, and pleon; C, right P2–P4 coxae and basis-ischia (denuded); D, left P2–P4 coxae and basis-ischia (denuded); E–H, right P2–P5, respectively (all to same scale); I, right P5 pseudochela.

Fig. 30. Colour in life. A, Gordonopsis hera, new species, holotype ovigerous female (21.8 × 31.2 mm) (MNHN-IU-2013-2245), Papua New Guinea; B, G. ceto, new species, holotype female (9.3 × 13.6 mm) (NTOU), South China Sea; C, G. velutina, new species, holotype female (20.8 × 27.8 mm) (MNHN-IU-2013-2269), Admiralty Islands. Photographs: A, C, Laure Corbari (MNHN); B, Chan Tin-Yam (NTOU).