Bioacoustics of Chinapotamon halangense

Remarks. Chinapotamon halangense sp. nov. can be distinguished from all other Chinapotamon species by the combination of the following characters: (1) medium sized species ( CW of mature individuals range between 27.2–34.9 mm ); (2) carapace subovate, dorsal surface convex, relatively smooth; (3) distinct epigastric and postfrontal cristae; (4) deep cleft between external orbital and epibranchial teeth; (5) anterolateral margins with distinct cristae; (6) anterolateral region gently rugose; (7) concavity between frontal margin lobes broad and shallow; (8) male major chela with oblate wide gap when closed; (9) ambulatory legs relatively slender; (10) sternites 3 and 4 completely fused, without a trace of groove demarcating suture; (11) subterminal article of male first gonopod is relatively slender, proximal half trapezoidal, distal half gently tapering distally; and (12) terminal article slender, bent outwards at about 25 °, slightly upcurved distally. Among described species of Chinapotamon , C. depressum ( Dai, Song, Li & Liang, 1980 ) is morphologically closest to C. halangense sp. nov. In fact, C. halangense sp. nov. was previously referred to C. cf. depressum by Le et al., 2024 , with references to the descriptions and illustrations by Dai and Naiyanetr (1994) and Dai (1999) . The species shares affinities with C. depressum sensu stricto , in terms of medium adult carapace size, the relatively broad G 1 subterminal article and the G 1 terminal article being similarly bent outwards at about 25 ° (cf. Dai et al. 1980 : fig. 3; Dai 1999 : fig. 43). Recent photographs of the holotype specimen of C. depressum in CAS have, however, revealed some discrepancies in the G 1 morphology, when compared to the illustrations in Dai et al. (1980) and Dai (1999) . Upon close examination, the new species can be distinguished from C. depressum by the following consistent differences: (1) subovate and smooth carapace (Fig. 1 A ) (vs. carapace subquadrate and comparatively rugose, particularly around branchial regions, cf. Fig. 5 A ); (2) epigastric and postorbital cristae faint (Fig. 1 A ) (vs. well-developed epigastric and postorbital cristae, cf. Fig. 5 ); (3) external orbital tooth positioned lower than frontal margin (Fig. 1 A ) (vs. external orbital tooth positioned higher than frontal margin, cf. Fig. 5 ); (4) suture separating sternites 3 and 4 barely visible (Fig. 1 A ) (vs. suture separating sternites 3 and 4 prominent, cf. Fig. 5 ); (5) ambulatory legs slenderer, merus and propodus of last ambulatory leg 3.5 and 2.3 times as long as wide respectively (Fig. 1 A ) (vs. ambulatory legs stouter, merus and propodus of last ambulatory 3.3 and 2.1 times as long as wide, respectively, cf. Fig. 5 ; Dai 1999 ; Ng 2017 : table 1; Zou et al. 2018 : table 2); (6) major chela fingers forming large ovate gape when closed (Fig. 1 E ) (vs. major chela fingers forming no gape when closed, cf. Fig. 5 ; Dai 1999 : pl. 4, fig. 5; cf. Zou et al. 2018 : table 2); (7) telson broadly triangular, lateral margins slightly convex (Fig. 2 A ) (vs. telson acutely triangular, lateral margins straight, cf. Fig. 5 ); and (8) G 1 subterminal article basal part proportionally longer, with shorter, broader neck-like distal half (Fig. 3 ) (vs. G 1 subterminal article basal part proportionally shorter, to proximal third of article, with longer, more slender distal neck-like part, cf. Fig. 5 D, E ).