Capitamon clarki n. sp.

(Figs 8; 9; 10)

urn:lsid:zoobank.org:act: B9049FED-7231-43FC-B80D-7ACFDF268F42

Potamon beieri – Pretzmann 1966b: 301, pl. 4, fig. 12; pl. 5, figs 16- 18 [not Potamon beieri Pretzmann, 1966].

Potamiscus beieri – Brandis 2000: 75 (in part) [not Potamon beieri Pretzmann, 1966].

TYPE MATERIAL. — Holotype. ♂ (42.1 × 32.9 mm); “ Burma ” [probably from Nagaland, India]; [c. 26°0’0”N, 95°0’0”E]; [alt. c. 1200 m]; no date; Captain Butler leg.; NHM 1909.5.1.1 (“Presd: Indian Museum” “4115/4”).

DIAGNOSIS. — Carapace ovate, broader than long (CW/CL = 1.3), relatively high (CH /CW = 0.5); epigastric cristae well-developed, rugose; postorbital cristae well-developed, relatively sharp, oblique in dorsal view; external orbital angle triangular, with short outer margin, c. 2 × inner margin; epibranchial tooth low, blunt, positioned above level of postorbital cristae; cervical grooves continuous, reaching to level of postorbital cristae; epistome posterior margin with well-developed, triangular median tooth, outer parts sloping downwards laterally (Figs 8A; 9A, C). Third maxilliped exopod with short flagellum, equal to half width of merus (Fig. 9B). Chelipeds rugose, subequal, inner distal tooth on carpus relatively broad (Figs 8A; 9E). Male s3/s4 shallow, running from sternopleonal cavity to lateral edges of sternum (Fig. 8B, E). Male pleonal somite 6 relatively narrower (proximal width c. 1.9 × medial length), longer than pleonal somite 5, with almost straight lateral margins (Figs 8B; 9D). Male telson relatively broader (proximal width c. 1.3 × medial length), with gently concave lateral margins (Figs 8B; 9D). G1 ultimate article relatively less strongly bent at angle of about 75° from longitudinal axis, with straight outer margin, dorsal flap relatively low, broadly triangular (Figs 8C; 10A, B, D). G2 c. 1.2 × length of G1; ultimate article long, c. 0.5 × length of penultimate article (Figs 8C, D; 10A, C).

ETYMOLOGY. — The species is named after English carcinologist Dr Paul Clark, the curator of Crustacea in the NHM, whose help with the collections was important in helping the authors solve the confusion with I. beieri . The species name is conceived as a noun in the genitive singular.

GEOGRAPHICAL DISTRIBUTION. — The precise geographical distribution of C. clarki n. gen., n. sp. is not known (see Remarks for I. beieri). The species is possibly originated from Nagaland state of northeastern India (Fig. 1).

REMARKS

Capitamon clarki n. gen., n. sp. has a relatively high carapace (CH / CW = 0.5) (Fig. 9C) among the nominal species of the genus with the relatively low carapace (CH /CW = 0.4) (Figs 5B; 12B; 15B; see Pati et al. 2020: fig. 2b). While C. clarki n. gen., n. sp. most resembles C. capitatum n. gen., n. sp. in the structure of the G1 ultimate article (see Remarks for C. capitatum n. gen., n. sp.), C. clarki n. gen., n. sp. also resembles C. manipurense n. comb. as both have a G1 ultimate article with the straight outer margin and the relatively low, broadly triangular dorsal flap (Figs 8C; 10A, B, D; 11A, C-E; see Pati et al. 2020: figs 4a-d; 5a-c). The G1 ultimate article, however, is little more strongly bent at an angle of about 75° from longitudinal axis of the G 1 in C. clarki n. gen., n. sp. (Figs 8C; 10A), while it is little less strongly bent at an angle of about 60° from longitudinal axis of the G 1 in C. manipurense n. comb. (Fig. 11D, E; see Pati et al. 2020: figs 4a, d; 5a, c). Capitamon clarki n. gen., n. sp. can be also distinguished from C. manipurense n. comb. by the shallow male s3/s4, running from the sternopleonal cavity to the lateral edges of the sternum (Fig. 8B, E) (vs male s3/s4 indiscernible except for two short lateral clefts; see Pati et al. 2020: figs 1b; 2e), and the relatively broader male telson, proximal width c. 1.3 times the medial length, with the lateral margins gently concave (Figs 8B; 9D) (vs male telson relatively narrower, proximal width c. 1.2 times the medial length, with the lateral margins strongly concave; see Pati et al. 2020: figs 1b; 2d).