Sinopotamon gaocuense, 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 : 57-60

Sinopotamon gaocuense spec. nov.

( Figs. 7–9 )

Material examined. Holotype: male, 24.5× 28.9 mm, NCU MCP 2008.0005, Jinjiang River, Xueli Village (ca. 27°52’32’’N 109°47’45’’E), Gaocun Rural, Mayang Miao autonomous county, Hu’nan Province, China, coll. Huilin Duan & Xianmin Zhou, 26 Jul. 2005.

Description. Carapace ( Fig. 7 a) squarish, widest across middle of anterolateral margins, CW 1.78 times (n = 1) CL; dorsal surface gently convex longitudinally, transversely, rough, with short setae; epigastric crista raised, postorbital crista short, cervical groove indistinct, H-shaped gastric groove distinct; anterolateral to posterolateral regions with short rows of granules. Front directed anterior-downward, concave medially. Frontal, supra-, infraorbital margins ( Fig. 7 b) cristate, granulated, infraorbital margin with larger granules, with concavity below external orbital angle; suborbital region only slightly granulated, pterygostomial regions with scattered granules. External orbital angle narrow, directed anteriorly, outer margin about 2.5 times longer than inner margin, outer margin fringed with two small teeth, epibranchital tooth long, sharp, disconnected from external orbital angle by V-shaped notch, anterolateral margin slightly convex, lined with 5–6 sharp teeth. Antennular fossa oblong; epistome with posterior margin sinuous, cristate, median lobe composed of one elongate granule.

Palp of mandible three-segmented, with terminal segment simple. Third maxilliped ( Figs. 7 b, 8) rectangular, midlength of ischium about 2 times that of merus, exopod reaching proximal third of outer margin of merus, inner margin of merus concave, flagellum distinct, not reaching inner end of merus.

Thoracic sternites 2, 3 ( Fig. 8 ) demarcated by distinct suture, suture between sternites 3, 4 indiscernible. Abdominal cavity reaching imaginary line joining posterior margins of cheliped coxae, cavity wide, distance between inner ends of sutures between thoracic sternites 4, 5 as wide as half length of distance between sternal condyles; sternal condyle on proximal two-fifths 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.

Chelipeds ( Fig. 7 ) similar in males; merus granulated on dorsal surface, subdistal dorsal tooth narrow, lobe-like, ventral margins granulated, sparsely lined with 4–6 conical teeth; carpus with sharp, long inner angle, small protuberance below angle; palm with moderately convex outer surface, not rough, length about 1.5 times height; fingers as long as palm, gape narrow when chela closed, cutting edge lined with low teeth.

Ambulatory legs ( Fig. 7 a) moderately long, with scattered short setae, second longest when stretched laterally; meri with subterminal angle on anterior margin; dactyli longer than respective propodi.

Male first abdominal segment with plate-like ridge on distal end of exposed area; third segment widest; telson triangular, width 1.34 times length (n = 1), 1.15 times (n = 1) longer than sixth segment, sixth segment width 2.06 times length (n = 1). G1 ( Figs. 9 a–c) slender, distal third curved inwards, proximal outer part of subterminal segment concave, disto-dorsal margin of subterminal segment concave; terminal, subterminal segments demarcated by membrane; terminal segment about one-fifth length of total length of G1, base of tip of terminal segment curved inwards, tip directed anteriorly. G2 ( Fig. 9 d) slightly shorter than G1, flagellum about one-third length of narrowed part of basal segment of G2.

Etymology. The species is named after the type locality, Gaocun Rural, Mayang Miao autonomous county, Hu’nan Province, China.

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

Remarks. Sinopotamon gaocuense spec. nov. can be characterized by the sharp, saw-edged anterolateral margin of the carapace and straight G1, which are also seen in S. yueyangense Dai, 1995 , and S. lansi ( Doflein, 1902) . Sinopotamon gaocuense can be distinguished from S. yueyangense Dai, 1995 , by its narrower carapace (vs. wider), the moderately triangular telson (vs. telson narrower and longer), the moderately long anterolateral teeth (vs. much longer), and an anteriorly directed tip of the terminal segment of the G1 (vs. tip directed inwards) [ Figs. 7–9 (a-c); Dai 1995: Fig. 3 (2, 4–6), Pl. 1(6); Dai 1999: Fig. 120(2, 4–6), Pl. 14(7)]. Sinopotamon gaocuense differs from S. lansi in its narrower carapace and the slender and anteriorly directed distal segment of the G1. In S. lansi , the carapace is wider, the distal segment of the G1 is stout, and the tip of the distal segment curves inwards [ Doflein 1902: Pl. 6(3); Dai 1999: Fig. 119(4–6), Pl. 14(6)].

Figures

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 7. Sinopotamon gaocuense spec. nov. (holotype male, 24.5 × 28.9 mm). a, habitus, dorsal view; b, cephalothorax, anterior view.

FIGURE 8. Ventral view of Sinopotamon gaocuense spec. nov. (holotype male, 24.5 × 28.9 mm).

FIGURE 9. Male gonopods of Sinopotamon gaocuense spec. nov. (holotype male, 24.5 × 28.9 mm). a, left G 1, ventral view; b, distal segment of left G 1, inner view; c, distal segment of left G 1, dorsal; d, left G 2. Scales, 1 mm.