A new long-legged terrestrial freshwater crab, Calcipotamon puglabrum gen. nov et sp. nov. (Crustacea: Decapoda: Potamidae), from Hainan Island, China Author Huang, Chao Author Huang, Sheng-Zhuo Author Shen, Zhi-Xin text Zootaxa 2020 2020-04-21 4766 3 447 456 journal article 22816 10.11646/zootaxa.4766.3.4 488c906f-a5c1-40cc-a69a-bf4c99f6046b 1175-5334 3765589 urn:lsid:zoobank.org:pub:739BB73C-0A2B-45C6-852A-A2596F897647 Genus Calcipotamon gen. nov. urn:lsid:zoobank.org:act: D878905F-653F-48BC-A4B1-0568766AC8C8 (Chinese name: ḂĪäǟ] ( Figs. 1–3 , 5 ) Type species. Calcipotamon puglabrum gen. nov. et sp. nov. , by current designation. Diagnosis. Carapace broader than long, smooth allover, generally convex ( Fig. 1 ); epigastric cristae smooth, low ( Fig. 1 ); external orbital tooth prominent, sharp, separated from anterolateral margin by gap ( Fig. 1 ). Median lobe of epistome broadly triangular ( Fig. 2A ). Maxilliped III with relatively broad ischium, exopod reaching beyond anterior edge of ischium, flagellum very short to absent ( Fig. 3A ). Cheliped palm surface smooth ( Figs. 1 , 3 F–G). Ambulatory legs very slender ( Fig. 1 ). Male anterior thoracic sternum relatively narrow, width 1.5 × length ( Fig. 2B ). Male pleon narrowly triangular ( Fig. 2C ). Female pleon ovate ( Fig. 4E ). G1 generally slender, terminal segment elongated with basal flap ( Fig. 3 C–E, H–I). G2 with long flagellum-like terminal segment ( Fig. 3B ). Female vulva positioned closely to one another, ovate, medium-sized, with relatively wide outer rim, reaching sternite suture V/VI but not VI/VII ( Fig. 2F ). FIGURE 1. Calcipotamon puglabrum gen. nov. et sp. nov. , dorsal habitus. (A) male holotype (31.6 × 24.5 mm), SYSBM 001961; (B) female paratype (31.5 × 24.6 mm), SYSBM 001964. FIGURE 2. Calcipotamon puglabrum gen. nov. et sp. nov. (A–D) male holotype (31.6 × 24.5 mm), SYSBM 001961; (E–F) female paratype (31.5 × 24.6 mm), SYSBM 001964. (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; (E) pleon, ventral view; (F) vulvae, ventral view. Etymology. The genus name is an arbitrary combination of Latin calcium and the type genus of Potamidae , Potamon . It alludes to the limestone habitat of the type species. Gender: neuter. Distribution. Changjiang Li Autonomous County, Hainan Island, China . Remarks. Calcipotamon gen. nov. is included in Potamiscinae sensu Yeo & Ng (2004) . Although superficially similar to Neotiwaripotamon , the new genus can be separated by the smooth carapace ( Fig. 1 ) (versus anterolateral and sub-orbital regions rugose, sub-hepatic and posterolateral striated in Neotiwaripotamon ), low and smooth postorbital cristate ( Fig. 1 ) (versus sharp in Neotiwaripotamon ; Dai 1999 : plate IV. figs. 2, 3), very short or absent flagellum of the maxilliped III exopod ( Fig. 3A ) (versus medium-length flagellum in Neotiwaripotamon ; Dai 1999 : fig. 40 (1), fig. 41 (1)), smooth cheliped palm surface ( Fig. 1 ) (versus granulated in Neotiwaripotamon ), very slender ambulatory legs ( Fig. 1 ) (versus relatively stouter in Neotiwaripotamon ; Dai 1999 : plate IV. fig. 2, 3) and terminal segment of G1 with large basal flap ( Figs. 3 C–E, H–I) (versus absent in Neotiwaripotamon ; Dai 1999 : figs. 40 (4), (5), 41 (4), (5)). FIGURE 3. Calcipotamon puglabrum gen. nov. et sp. nov. (A–C, F–G, H–I) male holotype (31.6 × 24.5 mm), SYSBM 001961; (D) male paratype (30.3 × 23.8 mm), SYSBM 001962; (E) male paratype (29.3 × 22.6 mm), AM P.104569. (A) Left maxilliped 3; (B) left G2, ventral view; (C–E) left G1s, ventral view; (F) minor chela (right); (G) major chela (left); (H) left G1 terminal segment, ventral view; (I) left G1 terminal segment, dorsal view. Scale bars: A–E, H–I = 1.0 mm; F–G = 5.0 mm. Calcipotamon gen. nov. is similar to Hainanpotamon in terms of G1 morphology, but can be immediately separated by its less swollen carapace ( Fig. 1 ) (very convex in Hainanpotamon ; Yeo & Naruse 2007 : fig. 1), smooth carapace ( Fig. 1 , 2A ) (Sub-orbital, sub-hepatic and pterygostomial granulated in Hainanpotamon ; Yeo & Naruse 2007 : fig. 1B), very short or absent flagellum of the maxilliped III exopod ( Fig. 3A ) (versus long flagellum in Hainanpotamon ; Yeo & Naruse 2007 : fig. 2A), epistome median lobe broadly triangular ( Fig. 2A ) (versus very broadly rounded in Hainanpotamon ; Yeo & Naruse 2007 : fig. 1B), relatively wider anterior thoracic sternum, width around 1.5 × length ( Fig. 2B ) (versus anterior thoracic sternites narrow in Hainanpotamon , width around 1.3 × length; Yeo & Naruse 2007 : fig. 2D), slender legs ( Fig. 1 ) (versus stout in Hainanpotamon ; Yeo & Naruse 2007 : fig. 1A). Calcipotamon gen. nov. is also morphologically similar to Tiwaripotamon , but can be separated by the broadly triangular epistome median lobe ( Fig. 2A ) (versus very broadly rounded in Tiwaripotamon ; Do et al. 2016 : fig. 3B, 4B, 5B), narrowly triangular pleon ( Fig. 2C ) (versus broadly triangular in Tiwaripotamon ; Dai 1999 : fig. 184 (2), fig. 185 (2)) and terminal segment of G1 with large basal flap (versus small to no flap in Tiwaripotamon ; Do et al. 2016 : fig. 2A–F; Dai 1999 : figs. 184 (4), (5), 185 (4), (5)).