The taxonomy of spider crabs of the genera Eurynome, Choniognathus, Seiitaiodes and Kasagia (Crustacea: Brachyura: Majidae) from southwest Indian Ocean Author Forges, Bertrand Richer De 0000-0002-4554-7953 b.richerdeforges@gmail.com Author Lee, Bee Yan Author Ng, Peter K. L. 0000-0002-4554-7953 b.richerdeforges@gmail.com text Zootaxa 2021 2021-10-07 5048 3 301 333 journal article 4058 10.11646/zootaxa.5048.3.1 6cf7dece-9a31-4cba-9497-664a0ffac9d8 1175-5326 5556341 951BE302-C0BF-4AA3-AE12-BBAC4EDEBAFB Kasagia elegans ( Stebbing, 1921 ) comb. nov. ( Figures 1B–D , 14 , 15A–C , 16A–C , 17A, B , 18 , 20A–C ) Eurynome elegans Stebbing, 1921: 454 , pl. 108.— Barnard, 1950: 57 , fig. 12d, e. Choniognathus elegans — Griffin & Tranter, 1986: 203 .— Ng et al ., 2008: 116 . Material examined. Neotype (herein designated): 1 male (cl 11.8 mm , pcl 9.8 mm , cw 7.9 mm , bcw 7.4 mm ) (MNHN-IU-2008-10340), stn CC 3159 , Mozambique Channel , 2355’S 3537’E, 148–152 m , coll. MAINBAZA, 15 April 2009 . Others : 1 female (cl 7.9 mm , pcl 6.3 mm , cw 4.9 mm , bcw 4.5 mm ) (MNHN-IU-2008-10339), stn CC3159 , Mozambique Channel , 2355’S 3537’E, 148–152 m , coll. MAINBAZA, 15 April 2009 .— 1 female (cl 11.9 mm , pcl 9.3 mm , cw 7.4 mm , bcw 6.9 mm ) (MNHN-IU-2010-77), stn DW3196, Madagascar ,1208’S 4856’E, 238–249 m , coll. MIRIKY, 28 June 2009 . Diagnosis. Postfrontal region of carapace relatively short ( Fig. 16A–C ); granules on posterior dorsal half of carapace closely packed ( Fig. 16A–C ). Base of pseudorostral spines separated from supraorbital eave by distinct gap ( Fig. 16A–C ). Supraocular eave distinctly more swollen, strongly carinate, separated from pseudorostral spine by a distinct cleft ( Fig. 16A–C ). Hepatic spine auriculiform, clearly lobiform, same size as postocular spine, directed outwards ( Fig. 16A–C ); branchial margin of carapace with 4 strong boletiform tubercles in ( Figs. 16B, C ; 18A ). Basal antennal article enlarged proximally, forming broad triangular tooth basally, with deep median longitudinal groove, margins prominently raised ( Figs. 17B , 18G ). Epistome forming 3 lobes. Buccal cavity wider anteriorly; ischium of third maxilliped with longitudinal row of 3 strong granules ( Figs. 17B , 18F ). Anterior part of the male thoracic sternum wide, smooth ( Fig. 18G ). Male pleon narrow, with long triangular telson ( Fig. 18G ). Chelipeds long, spiny; merus longer than carapace with 4 or 5 spines on each margin; carpus long with distal spine, distal part wider; chela long with 5 spines on outer border ( Fig. 15A , 18C, D ); fingers long slender.Ambulatory legs short, with dorsal margin of merus carinate. G1 relatively more sinuous ( Fig. 20A, B ). Type locality. Cape Vidal , Zululand , South Africa . FIGURE 14. Kasagia elegans ( Stebbing, 1921 ) comb. nov. , holotype female (cl 8.0 mm, cw 7.0 mm), South Africa. A, overall view; B, right third maxilliped; C, left third ambulatory leg; D, right fourth ambulatory leg (partially denuded); E, pleon. After Stebbing (1921 : pl. 108). FIGURE 15. Overall view. A, Kasagia elegans ( Stebbing, 1921 ) comb. nov. , neotype male (cl 11.8 mm, cw 7.9 mm) (MNHN-IU-2008-10340); B, K. elegans ( Stebbing, 1921 ) comb. nov. , female (cl 11.9 mm, cw 7.4 mm) (MNHN-IU-2010-77); C, K. elegans ( Stebbing, 1921 ) comb. nov. , female (cl 7.9 mm, cw 4.9 mm) (MNHN-IU-2008-10339); D, K. sudhakari Padate, Manjebrayakath & Ng, 2019 , male (cl 8.7 mm, cw 5.6 mm) (MNHN-IU-2017-8791); E, K. sudhakari Padate, Manjebrayakath & Ng, 2019 , ovigerous female (cl 8.1 mm, cw 5.2 mm) (MNHN-IU-2017-8791). FIGURE 16. Dorsal view of carapace. A, Kasagia elegans ( Stebbing, 1921 ) comb. nov. , female (cl 7.9 mm, cw 4.9 mm) (MNHN-IU-2008-10339); B, K. elegans ( Stebbing, 1921 ) comb. nov. , neotype male (cl 11.8 mm, cw 7.9 mm) (MNHN-IU-2008-10340); C, K. elegans ( Stebbing, 1921 ) comb. nov. , female (cl 11.9 mm, cw 7.4 mm) (MNHN-IU-2010-77); D, K. sudhakari Padate, Manjebrayakath & Ng, 2019 , male (cl 8.7 mm, cw 5.6 mm) (MNHN-IU-2017-8791); E, K. sudhakari Padate, Manjebrayakath & Ng, 2019 , ovigerous female (cl 8.1 mm, cw 5.2 mm) (MNHN-IU-2017-8791); F, K. arbastoi Richer de Forges & Ng, 2007 , paratype male (cl 12.6 mm, cw 9.2 mm) (ZRC 2013.176), Philippines. Remarks. Stebbing (1921: 454) described Eurynome elegans from a small female 8.0 × 7.0 mm (including spines) from Cape Vidal in South Africa and provided a rather schematic figure of the species ( Fig. 14 ). Barnard (1950: 57) did not examine Stebbing’s specimen but recorded another female (10.0 × 6.0 mm) from the same location, with his description matching that by Stebbing, and he also figured the gastric and cardiac regions of the carapace and the last ambulatory merus. The provenance of the type specimen of Eurynome elegans is not known. Ng et al . (2008: 219) discussed the problem with the type material of another species from the same paper, Pachygrapsus polyodous Stebbing, 1921 (now in Euchirograpsus H. Milne Edwards, 1853 , Plagusiidae ), noting that the type could not be located in South African Museum or the Natural History Museum in London where some of Stebbing’s material was donated. Some of his material has been found in London (e.g., see Ng & Clark 2010 ). At the author’s request, Paul Clark searched the NHM reference collection, but the specimen could not be located. Futhermore, the name was not in the register of material given to the museum. In all likelihood, the holotype of Eurynome elegans is no longer extant. Griffin & Tranter (1986: 203) transferred it to Choniognathus commenting that this was done on the basis of the type of carapace tubercles, the form of the basal antennal article and the first pleopod of the male. The G1 of the species, however, has never been recorded, although it is possible the authors examined specimens that were not recorded in their paper. The present three specimens are referred to Stebbing’s (1921) species. The smallest specimen (cl 7.9 mm , cw 4.9 mm , MNHN-IU-2008-10339) is similar in size to the holotype and shares all the key features of the species. The prominent auriculate and lobiform postorbital and hepatic spines are diagnostic, as are the carinate supraorbital eaves ( Figs. 15A–C , 16A–C ), agreeing with the original figures ( Fig. 14 ). The lateral spines of this female are acute and spinyform like in the holotype ( Fig. 16A ), but in the two larger specimens (including a male), these spines become distinctly fungiform in shape ( Fig. 16B, C ). As such, the species is assigned to Kasagia . FIGURE 17. A, B, Kasagia elegans ( Stebbing, 1921 ) comb. nov. , female (cl 11.9 mm, cw 7.4 mm) (MNHN-IU-2010-77); C, D, K. sudhakari Padate, Manjebrayakath & Ng, 2019 , male (cl 8.7 mm, cw 5.6 mm) (MNHN-IU-2017-8791). A, C, cephalothorax; B, D, ventral view showing antennules, antennae, epistome, buccal cavity and third maxillipeds. FIGURE 18. Kasagia elegans ( Stebbing, 1921 ) comb. nov. , neotype male (cl 11.8 mm, cw 7.9 mm) (MNHN-IU-2008-10340). A, dorsal view of anterior half of carapace; B, ventral view showing antennules, antennae, epistome, buccal cavity and third maxillipeds; C, ventral view of right cheliped; D, dorsal view of right cheliped; E, fourth ambulatory leg (partially denuded); F, right third maxilliped; G, ventral view of cephalothorax. Another similar species, K. sudhakari Padate, Manjebrayakath & Ng, 2019 , also occurs in the western Indian Ocean and is sympatric with K. elegans comb. nov. , it is useful to select a neotype for the latter species. This is especially considering that it is the oldest of the three Kasagia species known, the rather poor figures provided by Stebbing (1921) , and its close resemblance to K. arbastoi . A neotype will help stabilise the taxonomy of the whole genus. A male specimen (cl 11.8 mm , pcl 9.8 mm , cw 7.9 mm , bcw 7.4 mm , MNHN-IU-2008-10340) from the Mozambique Channel is here designated as the neotype of Eurynome elegans Stebbing, 1921 ( Figs. 1B , 15A , 16B , 18 , 20A–C, I ). This location is about 600 km to the northeast of the original type locality at Cape Vidal in South Africa but is in the same system.