Gordonopsis robusta, Ng & Padate & Saravanane, 2019

Ng, Peter K. L., Padate, Vinay P. & Saravanane, Narayanane, 2019, Gordonopsis robusta, a new species of deep-sea porter crab (Crustacea: Brachyura: Homolidae) from the Andaman Sea, India, Raffles Bulletin of Zoology 67, pp. 510-516 : 510-515

publication ID

https://doi.org/ 10.26107/RBZ-2019-0040

publication LSID

lsid:zoobank.org:pub:3E4342E3-02F9-48FA-A721-4CB4A0F37105

persistent identifier

https://treatment.plazi.org/id/CBC17B07-AD01-44EF-A529-A38DD737A4B6

taxon LSID

lsid:zoobank.org:act:CBC17B07-AD01-44EF-A529-A38DD737A4B6

treatment provided by

Carolina

scientific name

Gordonopsis robusta
status

sp. nov.

Gordonopsis robusta View in CoL , new species

( Figs. 1–4 View Fig View Fig View Fig View Fig )

Material examined. Holotype: male (44.9 x 33.5 mm) ( CMLRE IO /SS/BRC/00082), Andaman Sea, FORVSS

station 36708, 13.27°N, 93.26°E, 635 m, HSDT ( CV), coll. S. S. Cubelio, 26 November 2017. Paratype: young female (20.8 x 15.6 mm) ( CMLRE IO /SS/BRC/00083), same data as holotype GoogleMaps .

Diagnosis(based on holotype male). Carapace longitudinally ovate (CW/CL = 0.75), distinctly (1.75 times) wider posteriorly than anteriorly, with distinct lateral linea homolica (sensu Guinot & Richer de Forges, 1995); carapace high,

box-like in frontal view; dorsal carapace surface with welldefined regions, separated by broad, deep grooves; dorsal parts with numerous scattered setae that do not obscure surface; lateral parts with denser setae that partially obscures surface, especially dense on hepatic, pterygostomial and suborbital regions ( Figs. 1A, B View Fig ). Rostrum relatively long (RL/postrostral CL = 0.15), sharp, two obliquely directed pseudorostral spines shorter than rostrum (0.87 times RL), sharp ( Fig. 1B View Fig ). Eyes with short ocular peduncle, cornea prominent; no discernible orbit ( Fig. 1 View Fig B–D). Hepatic area not inflated, with short obliquely directed spine ( Fig. 1B, C View Fig ). Gastric area without spines ( Figs. 1B View Fig , 4B View Fig ). Gastric groove well marked, with distinct ovate gastric fossae anterior to it ( Fig. 1B View Fig ). Cardiac region swollen; branchial region inflated, with distinct branchio-cardiac grooves ( Fig. 1B View Fig ). Lateroposterior tubercle on carapace distinct, sharp ( Fig. 1B View Fig ). Base of antenna with stout, slightly curved spine ( Fig. 1D View Fig ). Antennal flagellum short; second and third articles thick, setose. Epistome short ( Fig. 1D View Fig ). Third maxilliped pediform, merus with sharp, dentiform external angle ( Fig. 2A View Fig ). Chelipeds ca. 1.50 times as long as CL, reaching only to P2 propodus when out-stretched; fingers long; palm long, slender, gently compressed laterally, dorsal margin with three rows of spinules, outer surface with five indistinct rows of well-spaced granules, internal surface with two rows of spinules, dorsal row shorter, ventral row extending to base of pollex; carpus longitudinally ovate, outer margin with eight to ten short spines, inner margin with five or six prominent spines, that on subdistal angle largest; merus triangular in cross-section, relatively long, curved, with eight spines on upper border, seven to nine spines on lower border, those on distal part longer, sharper, those on proximal part low ( Fig. 1A View Fig , 2 View Fig B–E). Ambulatory legs relatively long, with distal edge of P5 merus just reaching beyond lateroposterior tubercle when folded anteriorly; basis-ischium with small granules, without distinct spines; P2 merus with five spines on upper border, one distal spine, ventral margin with three or four spines and one proximal tubercle; P3 merus with five spines on upper border, one distal spine, ventral margin with one or two tubercles; P4 missing ( Figs. 1A View Fig , 2F, G View Fig ). P5 short, oriented dorsally, merus without spines on both margins, just reaching gastric groove when folded anteriorly; carpus long, propodus short, enlarged, forming prominent pseudochela with dactylus curved; distal border of propodus with row of large spine-like setae opposed to similar row on side of dactylus ( Fig. 2 View Fig H–J). Pleon longitudinally ovate, with six free somites and telson, telson triangular with convex lateral margins and sharp tip ( Fig. 3 View Fig A–C). G1 short, stout, distal part prominently narrowed with subtruncate tip ( Fig. 3 View Fig E–H). G2 stout, tubular, length subequal to G1, basal portion slightly dilated, covered with long setae, distal portion cup-shaped ( Fig. 3I, J View Fig ).

Variation. The paratype female is not adult, with the pleon not fully enlarged, not dome-shaped and the pleopods not strongly setose ( Fig. 4C View Fig ). Its rostrum is also proportionately shorter than that of the holotype male ( Fig. 4B View Fig ), being only subequal in length to the lateral pseudorostral spines. The armature on the ambulatory legs of the paratype female are as follow: P2 merus with five spines on upper border, one distal spine, ventral margin with one tubercle; P3 merus with five spines on upper border, one distal spine, ventral margin with one tubercle; and P4 with three spines on upper border, one distal spine, ventral margin unarmed ( Fig. 4A View Fig ). The differences with the holotype male are mainly for the ventral margin, with less spines in the paratype female and this is probably due to its juvenile condition. The chelipeds and P5 of the paratype female ( Fig. 4A, B, E, F View Fig ) agree with the holotype male in most aspects, with small differences in number of spines probably due to its small size. The carpus of the female cheliped has eight short spines on the outer margin with the distalmost one longest while the inner margin has five spines; and the merus has six spines on the outer margin, six short spines on the inner margin and two strong spines on the upper distal margin ( Fig. 4A, E, F View Fig ). The spines in the female are all proportionately shorter and weaker than those of the male.

Etymology. The species name alludes to the overall stouter appearance of the new species, with its wider carapace and proportionately shorter ambulatory legs.

Remarks. Gordonopsis robusta , new species, differs from G. profundorum s. str. and G. pacifica most obviously in possessing a distinctly stouter and proportionately broader carapace with the posterior part clearly wider ( Figs. 1B View Fig , 4B View Fig ); in G. profundorum and G. pacifica , the carapace is more slender and less inflated with the anterior and posterior parts subequal in width (cf. Alcock, 1901: pl. 5, fig. 22; Doflein, 1904: pl. 7, figs. 1, 2; Guinot & Richer de Forges, 1995: figs. 63d–f, 64A; Takeda & Suyama, 2019: fig. 2). The carapace differences cannot be accounted for by size because the paratype female of G. robusta is of a similar size to the material reported by Doflein (1904) and Guinot & Richer de Forges (1995), as is the holotype male of G. robusta . Another clear difference is the proportionately shorter ambulatory legs (P2–P5) of G. robusta ( Figs. 1A View Fig , 2 View Fig F–H, J), with the meri in particular stouter and shorter in form with the P5 merus reaching the gastric groove when folded anteriorly ( Figs. 2J View Fig , 4B View Fig ). In G. profundorum and G. pacifica , the ambulatory legs are prominently longer and when the P5 is folded anteriorly, the merus clearly overreaches the gastric groove, reaching the median gastric regions (cf. Alcock, 1901: pl. 5, fig. 22; Doflein, 1904: pl. 7, figs. 1, 2; Guinot & Richer de Forges, 1995: fig. 63e; Takeda & Suyama, 2019: fig. 2). There are also differences in the degree of setation on the carapace, chelipeds and ambulatory legs as well as armature on the ambulatory meri. The tomentum on the two type specimens of G. robusta is dense and partially obscures the surface and margins ( Figs. 1 View Fig , 2 View Fig ) (versus distinctly more glabrous in G. profundorum ). The degree of tomentum in G. pacifica is similar to that of G. robusta (cf. Takeda & Suyama, 2019: fig. 3A–D). The dorsal meral armature of the P2–P 4 in G. robusta is as follows: there are five spines on P2 ( Fig. 2F View Fig ) (versus four in G. profundorum ; three in G. pacifica ); five spines on P3 ( Fig. 2G View Fig ) (versus three in G. profundorum and G. pacifica ); and three spines on P4 ( Fig. 4A View Fig ) (versus two or three in G. profundorum and G. pacifica ) (cf. Alcock, 1901: pl. 5, fig. 22; Doflein, 1904: pl. 7, figs. 1, 2; Takeda & Suyama, 2019: 48; P. K. L. Ng & B. Richer de Forges, unpublished data).

Guinot & Richer de Forges (1995) commented that their material from the Maldives, Seychelles, and Madagascar differed from the descriptions and figures of G. profundorum s. str. (sensu Alcock & Anderson, 1899; Alcock, 1901; Doflein, 1904) in having a short lateroposterior carapace spine, a less pyriform carapace and relatively longer and more slender ambulatory legs. As such, they preferred to identify their material as “ Gordonopsis aff. profundorum ”. Their material (as well as that of Doflein, 1904) is now reappraised as part of the revision of the genus but this does not affect the discussion of the new species.

IO

Instituto de Oceanografia da Universidade de Lisboa

CV

Municipal Museum of Chungking

Kingdom

Animalia

Phylum

Arthropoda

Class

Malacostraca

Order

Decapoda

Family

Homolidae

Genus

Gordonopsis

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