Sinopotamon mayangense, Naruse, Tohru, Yeo, Darren C. J. & Zhou, Xianmin, 2008

Naruse, Tohru, Yeo, Darren C. J. & Zhou, Xianmin, 2008, Five new species of freshwater crabs (Crustacea: Decapoda: Brachyura: Potamidae) from China, Zootaxa 1812, pp. 49-68 : 60-62

Sinopotamon mayangense spec. nov.

( Figs. 10–12 )

Material examined. Holotype: male, 26.5× 33.4 mm, NCU MCP 2008.0006, Jinjiang River, Xueli Village (ca. 27°49’ 0 1’’N 109°48’ 0 3’’E), Gaocun Rural, Mayang Miao autonomous county, Hu’nan Province, China, coll. Huilin Duan & Xianmin Zhou, 26 Jul. 2005.

Paratypes: 1 male, 21.7× 26.7 mm, 7 females, 21.9×27.4–24.9× 31.5 mm, NCU MCP 2008.0007, data same as holotype; 2 males, 26.9×34.6, 26.9× 33.2 mm, 4 females, 23.8×29.4–28.6× 36.6 mm, ZRC 2008.0015, data same as holotype; 3 males, 22.9×28.0–24.5× 30.2 mm, 2 females, 21.6×28.1, 24.6× 31.4 mm, NMNS- 5752-001, data same as holotype.

Description. Carapace ( Fig. 10 a) broader than long, widest across middle of anterolateral margins, CW 1.22–1.30 times (mean 1.26, n = 12) CL; dorsal surface flat, smooth; epigastric, postorbital cristae oblique; cervical, H-shaped gastric grooves shallow, indistinct; anterolateral region with elongated granules. Front gently directed downwards, anterior margin straight, frontal region granulated. Supra-, infraorbital margins ( Fig. 10 b) cristate, lined with small granules, only inner part of suborbital region, anterior part of pterygostomial region with granules. External orbital angle directed anterior-inward, outer margin about 3 times longer than inner margin; epibranchital tooth distinct, anterolateral margin convex laterally, granules distinct. Antennular fossa rectangular; epistome with posterior margin cristate, lined with granules, with sharp triangular median tooth.

Palp of mandible three-segmented, with terminal segment simple. Third maxilliped ( Figs. 10 b, 11) rectangular, midlength of ischium about 2 times that of merus, exopod reaching proximal two-fifths of outer margin of merus, flagellum long, slightly shorter than width of merus.

Thoracic sternites 2, 3 demarcated by unevenness, suture between sternites 3, 4 indiscernible. Abdominal cavity reaching imaginary line joining posterior quarter of cheliped coxae, cavity relatively wide, distance between inner ends of sutures between thoracic sternites 4, 5 longer than third length of distance between sternal condyles; sternal condyle on slightly below middle of thoracic sternite 5; thoracic sternite 8 demarcated medially by uninterrupted longitudinal median line, without transverse ridge at inner ends of sutures between thoracic sternites 7, 8.

Cheliped ( Fig. 10 a) slightly asymmetrical, major cheliped stouter, longer than minor; merus granulated on dorsal, ventral margins; carpus with strong, sharp inner angle, small tooth below angle; palm smooth, height shorter than length; fingers as long as palm, gape narrow when closed, cutting edge lined with low teeth.

Ambulatory legs ( Fig. 10 a) moderately long, surfaces rough, anterior margin of meri lined with obtuse low teeth, moderately long, second, third longest when stretched laterally; dactyli as long as respective propodi in P2–P4, slightly shorter in P5.

Abdomen ( Fig. 11 ) with regularly divergent lateral margins, first abdominal segment with transverse ridge; third segment widest; telson with lateral margins concave proximally, width 1.26 times length (n = 1), 1.29 times (n = 1) longer than sixth segment, sixth segment width 2.21 times length (n = 1). G1 ( Figs. 12 a, b) stout; proximal outer part of subterminal segment concave; outer ventral layer of subterminal segment with suture along inner margin, distal part of subterminal segment raised ventrally, distodorsal part concave medially, boundary between subterminal, terminal segments membrane-like; distal segment length quarter of total G1 length, strongly bent inwards, opening on subdistal part of anterior surface. G2 ( Fig. 12 c) as long as G1, flagellum ribbon-like, about three-fifths length of narrowed part of basal segment.

Distribution and habitat. Sinopotamon mayangense spec. nov. is found from the type locality (Gaocun Rural, Mayang Miao autonomous county, Hu’nan Province, China;> 200m asl.) Hu’nan (mayang) The species was found from under screes in a rivulet.

Remarks. Sinopotamon mayangense spec. nov. is similar to S. bilobatum Dai & Jiang, 1991 , and S. nanlingense Dai & Jiang, 1991 , in the short, stout and bent distal segment of the G1 of the three species. Sinopotamon mayangense , however, can be distinguished from S. bilobatum by the strong bent (ca. 60°) of the terminal segment of the G1 [vs. blunt and less bent (ca. 45°)], a tapering tip of the terminal segment (vs. bilobate distal tips), and the subdistal opening of the terminal segment (vs. opening distal) [ Figs. 12 a, b; Dai & Jiang 1991: Fig. 2 (3, 4); Dai 1999: Fig. 123 (4, 5)].

Sinopotamon mayangense can be differentiated from S. nanlingense by the strongly bent (ca. 60°) terminal segment of the G1 [vs. less bent (ca. 45°)] and rounded outer margin of the terminal segment of the G1 (vs. distal third narrowed, so that the lateral margin is angular) [ Figs. 12 a, b; Dai & Jiang 1991: Fig. 3 (3, 4); Dai 1999: Fig. 173 (4, 5)].

Figures

FIGURE 2. Ventral view of Latopotamon xuanweiense spec. nov. (holotype male, 20.2 × 25.4 mm).

FIGURE 3. Male gonopods of Latopotamon xuanweiense spec. nov. (paratype male, 21.0 × 26.2 mm). a, left G 1, ventral view; b, distal segment of left G 1, vento-outer view; c, distal segment of left G 1, dorso-inner view; d, left G 2. Scales, 1 mm.

FIGURE 10. Sinopotamon mayangense spec. nov. (holotype male, 26.5 × 33.4 mm). a, habitus, dorsal view; b, cephalothorax, anterior view.

FIGURE 11. Ventral view of Sinopotamon mayangense spec. nov. (holotype male, 26.5 × 33.4 mm).

FIGURE 12. Male gonopods of Sinopotamon mayangense spec. nov. (holotype male, 26.5 × 33.4 mm). a, left G 1, ventral view; b, distal segment of left G 1, dorsal view; c, left G 2.