Jianghuaimon, Zhao & Xu & Huang, 2022

Zhao, Jun-Da, Xu, Yi-Yang & Huang, Chao, 2022, Jianghuaimon dabiense gen. nov. et sp. nov (Crustacea: Decapoda: Potamidae), a new genus and new species of freshwater crab from eastern-central China, Zootaxa 5168 (4), pp. 431-440 : 432

Genus Jianghuaimon gen. nov.

[Chinese name: ü淮ēøĸ]

Type Species. Jianghuaimon dabiense gen. nov. et sp. nov., by present designation.

Diagnosis. Small sized (CW <25 mm). Carapace subquadrate, flat, dorsal surface pitted ( Fig. 1 ); epigastric cristae low; not confluent with postorbital cristae ( Fig.1 ); external orbital angle bluntly triangular, almost straight ( Fig. 1 ). Epistomial median lobe narrowly triangular ( Fig. 2A ). Maxilliped III with relatively broad ischium, exopod reaching beyond anterior edge of ischium, with long flagellum ( Fig. 3A ). Cheliped palm surface relatively rugose ( Fig. 3F–G ). Male anterior thoracic sternum wide, width 1.8 × length ( Fig. 2B ). Male pleon broadly triangular, tip of telson semicircular ( Fig. 2C ). G1 generally slender, pointing anterolaterally, terminal segment large and stout with wide opening at truncate tip, inner margin rounded ( Fig. 3C–E, H–I ). G2 with subquadrate basal segment ( Fig. 3B ). Female vulva ovate, large, located within sternite VI ( Fig. 2F ).

Etymology. The genus name is an arbitrary combination of the zoogeographic location of the type locality, the Jianghuai freshwater zoogeographic dominion ( Huang et al. 2020a), and the genus name, Potamon Savigny, 1816 . Gender: neuter.

Distribution. Huo Shan county, Lu’an city, Anhui province, China; Yingshan County, Huanggang City, Hubei Province, China.

Remarks. Jianghuaimon gen. nov. has a rather unexceptional external appearance and most closely resembles Bottapotamon Türkay & Dai, 1997 and Neilupotamon Türkay & Dai, 1997 in its small size (CW <30 mm), relatively flat carapace with regions distinct, bluntly triangular external orbital angle and slightly unequal chelipeds. Jianghuaimon gen. nov. also resembles Huananpotamon Dai & Ng, 1994 in general external appearance to some extent, its relatively small size (CW <30 mm), having stripe patterned ambulatory legs and a distinctive ovalshaped gold-colour pattern on the third maxilliped. However, Jianghuaimon gen. nov. markedly differs from Bottapotamon , Huananpotamon and Neilupotamon by its unique G1 structure, which is pointed anterolaterally, subterminal segment slightly curved inwards, terminal segment large and very stout, inner margin strongly convex, tip truncated with wide opening almost same width as terminal segment ( Fig. 3C–E, H–I ). In contrast, the G 1 in Bottapotamon is pointed anteromedially, with the subterminal segment generally straight, terminal segment large and slender, inner margin concave, tip truncated with opening smaller than terminal segment width (cf. Gao et al. 2019: fig. 5); in Huananpotamon , pointed anteriorly or anteromedially, with the distal part of subterminal segment neck-shaped, terminal segment slender, inner margin with flap or projection, with small opening at pointed tip (cf. Dai 1999: pls. 63–73); and in Neilupotamon , pointed anterolaterally, with the subterminal segment generally straight, terminal segment stout, inner margin almost straight to slightly convex, tip truncated with wide opening almost as wide as the terminal segment (cf. Dai 1999: pls. 201–204). Jianghuaimon gen. nov. can further be separated from Bottapotamon , Huananpotamon and Neilupotamon by differences in the carapace, male anterior thoracic sternites and male telson. See Table 1 for detailed comparisons. Moreover, Jianghuaimon gen. nov. was found to be syntopic with Longpotamon depressum , but can immediately be distinguished by its smaller size (CW <25 mm) (versus CW <50 mm in the latter), carapace anterolateral margin with 12–15 granules ( Fig. 1A ) (versus serrated, with 15–18 granules in the latter; Dai 1999: pl. XXII fig. 2), granules on anterolateral margin low and inconspicuous ( Fig. 1A ) (versus relatively large conspicuous in the latter; Dai 1999: pl. XXII fig. 2) and its G1 terminal segment large, stout, with rounded inner margin and wide opening at truncate tip ( Figs. 3C–E, H–I ) (versus relatively small G1 terminal segment with bifurcated tip in the latter; Dai 1999: pl. 179).

Figures

FIGURE 1. Jianghuaimon dabiense gen. nov. et sp. nov., dorsal habitus. (A) male holotype SYSBM002003; (B) female paratype SYSBM002007.

FIGURE 2. Jianghuaimon dabiense gen. nov. et sp. nov. (A–D) male holotype (20.4 × 15.7 mm), SYSBM002003; (E–F) female paratype (16.4 × 13.0 mm), SYSBM002007; (A) Cephalothorax, anterior view; (B) anterior thoracic sternum; (C) anterior thoracic sternum and pleon, ventral view; (D) sterno-pleonal cavity with G1 in situ, ventral view. Female paratype (mm): (E) pleon, ventral view; (F) vulvae, ventral view.

FIGURE 3. Jianghuaimon dabienese gen. nov. et sp. nov. (A–C, F–G, H–I) male holotype (20.4 × 15.7 mm), SYSBM002003; (D) male paratype (16.9 × 12.9 mm), NNU 20105JD1; (E) male paratype (17.5 × 13.2 mm), SYSBM002008; (A) right third maxilliped; (B) left G2, ventral view; (C–E) left G1s, ventral view; (F) major chela (right); (G) minor chela (left); (H) left G1 terminal segment, dorsal view; (I) left G1 terminal segment, ventral view. Scale bars: A–G = 2.0 mm; H–I = 1.0 mm.