A revision of Carcinoplax abyssicola (Miers, 1885) and seven related species of Carcinoplax H. Milne Edwards, 1852, with the description of two new species and an updated key to the genus (Crustacea, Decapoda, Brachyura, Goneplacidae) Author Ng, Peter K. L. Lee Kong Chian Natural History Museum, National University of Singapore, 2 Conservatory Drive, Singapore 117377 (Republic of Singapore) Author Castro, Peter Biological Sciences Department, California State Polytechnic University, Pomona, CA 91768 (United States) pcastro @ cpp. edu (corresponding author) pcastro@cpp.edu text Zoosystema 2020 2020-06-09 42 17 239 284 journal article 21685 10.5252/zoosystema2020v42a17 d5f2bb15-439a-45d2-9121-beb168fcb637 1638-9387 3894945 urn:lsid:zoobank.org:pub:52C73176-6867-4415-A6FA-BAD328E9781D Carcinoplax adelphia n. sp. ( Figs 19 A-H; 20 A-I; 25 F-I; 27 E, F) urn:lsid:zoobank.org:act: 4AA2E938-5F47-4B42-8BCC-83A2CD1D8E18 TYPE MATERIAL. — Holotype . Vanuatu • ♂ , 19.4 × 25.4 mm ; Vanuatu ; MNHN-IU-2016-8002 . Paratypes . Vanuatu • 2 ♀ , largest 16.9 × 22.4 mm ; SANTO 2006, stn AT19, S. Urelapa I.; 15°41’S , 167°01’E ; 503-600 m depth ; 21.IX.2006 , ZRC 2009.0997 • 1 ovigerous ♀ , 14.4 × 19.0 mm; SANTO 2006, stn AT96, Big Bay , Santo ; 15°06.9’S , 166°52.8’E ; 328-354 m depth ; 14.X.2006 ; ZRC 2018.1412 • 1 ♀ , 16.9 × 22.4 mm , 1 ♂ , 15.7 × 21.2 mm ; SANTO 2006, stn AT98, Big Bay ; 15°06.6’S , 166°50.6’E ; 347-394 m depth ; 14.X.2006 ; ZRC 2009.0922 • 5 ♀ , 16.5 × 22.5 mm , 2 ♂ , larger one cl 12.3 mm , damaged; same data as ZRC 2009.0922; ZRC 2009.0998 • 1 ♂ , 18.8 × 29.9 mm ; SANTO 2006, stn AT99, Big Bay ; 15°05.5’S , 166°50.9’E ; 351-395 m depth ; 14.X.2006 ; ZRC 2008.0907 • 10 ♀ , largest 13.6 × 18.3 mm , 15.9 × 20.8 mm , 1 ♂ , 16.0 × 22.9 mm ; same data as ZRC 2008.0907; ZRC 2009.0996 • 1 ovigerous ♀ , 17.7 × 24.2 mm ; same data as ZRC 2008.0907; ZRC 2018.1413 • 3 ♀ , largest 15.1 × 19.3 mm , 14 ♂ ; SANTO 2006, stn AT100, Big Bay ; 15°06.0’S , 166°51.4’E ; 399-416 m depth ; 14.X.2006 ; MNHN-IU-2016-8002 • 1 ovi- gerous ♀ , 8.5 × 11.2 mm , 1 ♂ , 7.6 × 11.2 mm ; SANTO 2006, stn AT121, W Malo I.; 15°38.7’S , 167°01.2’E ; 275-290 m depth ; 19.X.2006 , ZRC 2009.0989 • 1 ♂ , trap 3, no other data, MNHN-IU-2010-5546. TYPE LOCALITY. — Vanuatu , SANTO 2006; stn AT100, Big Bay; 15°06.0’S , 166°51.4’E ; 399-416 m depth. FIG. 18. — Carcinoplax fasciata Ng & Kumar, 2016 , holotype ♂ (25.8 × 19.3 mm) (DABFUK), India: A , overall habitus; B , dorsal view of carapace; C , frontal view of cephalothorax; D , posterior margin of epistome; E , thoracic sternum and pleon; F , left third maxilliped; G , dorsal view of carpus of left cheliped; H , dorsal view of carpus of right cheliped; I , outer view of right chela; J , outer view of left chela. FIG. 19. — Carcinoplax adelphia n. sp. ,holotype ♂ (19.4 × 25.4 mm) (MNHN-IU-2016-8002), Vanuatu: A , overall habitus; B , dorsal view of carapace; C , frontal view of cephalothorax; D , posterior margin of epistome; E , left third maxilliped; F , dorsal view of right cheliped; G , thoracic sternum and pleon; H , outer view of chelae. FIG. 20. — Carcinoplax adelphia n. sp. , paratype ♀ (16.9 × 22.4 mm) (ZRC 2009.0992), Vanuatu: A , overall habitus; B , dorsal view of carapace; C , frontal view of cephalothorax; D , posterior margin of epistome; E , left third maxilliped; F , dorsal view of carpus of right cheliped; G , thoracic sternum and pleon; H , sternopleonal cavity and vulvae; I , outer view of chelae. DIAGNOSIS. — Carapace ( Figs 19A, B ; 20A, B ; 27E, F ) quadrate, slightly wider than long (1.4 × wider than long in holotype ); slightly convex, smooth. Front ( Figs 19C, D ; 20C, D ) straight, slight notch between front, inner edge of supraorbital border. Rounded, short tooth on outer orbital angle; two slender, acutetipped anterolateral teeth on each side of carapace. Conspicuous granules on subhepatic, pterygostomial regions ( Figs 19C, D ; 20C, D ), becoming more pronounced in pterygostomial crest, ridge; short granules on anterior, dorsal surface of carapace. Posterior margin of epistome ( Figs 19D ; 20D ) straight, slight notch on each lateral margin. Distal 2/3 to half of fingers dark brown in females ( Fig. 20A, F, I ), males ( Fig. 19A, F, H ). Smooth, oblong “window” on inner, dorsal surface of cheliped propodi of some males ( Fig. 19F ). Inner (ventral), distal margin of cheliped carpus ( Figs 19F ; 20F ) with triangular tooth. P2-P5 ( Figs 19A ; 20A ; 27E, F ) moderately stout in appearance, P5 not reaching second anterolateral tooth. Male pleon ( Fig. 19G ) proportionally narrow. G1 ( Fig. 25 F-H) slender; pointed tip with scattered spinules; G2 ( Fig. 25I ) slender, nearly equal or slightly longer than G1, slightly curved flagellum, tip with two lateral spinules. ETYMOLOGY. — The name is derived from the Greek adelphos for ‘brother’ or ‘sister,’ alluding to the close affinities of the new species with C. specularis . The name is treated as a noun. COLOUR IN LIFE. — Orange with a semi-circular row of small white spots on each side of the carapace ( Fig. 27E, F ). GEOGRAPHICAL DISTRIBUTION. — Vanuatu . DEPTH. — Present in samples collected at depths of 275- 600 m . REMARKS Carcinoplax adelphia n. sp. and C. specularis are superficially very similar, including the spots on the dorsal surface of the carapace shown in life ( Fig. 27E, F for C. adelphia n. sp. ; Fig. 27D for C. specularis ). They are, however, easily separated by the structure of their G1s. The G1 is relatively shorter and stouter in C. specularis ( Fig. 25A, B ,) than in C. adelphia n. sp. , which is more elongated, particularly the distinctly more slender distal half ( Fig. 25F ). Carcinoplax specularis can be also separated from allied species by the obtusely triangular median part of the posterior margin of its epistome, which extends beyond the lateral margins, with the lateral margins gently concave ( Figs 10D ; 11D ; 12D ) (median part very low and almost at the same level as the lateral margins, which are almost straight in C. adelphia n. sp. ; Figs 19D ; 20D ). Both share a similar colour pattern, with two unique semi-circular rows of white spots on the dorsal surface of the carapace of live individuals ( Fig. 27D for C. specularis ; Fig. 27E, F for C. adelphia n. sp. ). Like in C. specularis , a “window” on the chela was found in a few large males of C. adelphia n. sp. : 15.7 × 21.2 mm (ZRC 2009.0922), 18.8 × 29.9 mm (ZRC 2008.0907) and the holotype 19.4 × 25.4 mm (MNHN-IU-2016-8002). These are not obvious in females or juveniles.