Potamidae Ortmann 1896, new genus
Creators: name: Huang, Chao
name: Mao, Si Ying
name: Huang, Jian Rong
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Potamidae

description: Family Potamidae Ortmann, 1896
Yuexipotamon, new genus
Diagnosis. Carapace subquadrate, with dorsal surface slightly convex, surface pitted, rugose on anterolateral regions (Fig. 2 A); postorbital and epigastric cristae distinct, not confluent (Fig. 2 A); external orbital tooth bluntly triangular, separated from anterolateral margin by a narrow gap (Fig. 2 A,B); median lobe of posterior margin of epistome broadly triangular (Fig. 2 B); third maxilliped with relatively broad ischium, exopod of third maxilliped reaches beyond anterior edge of ischium, with short flagellum (Fig. 3 D); male abdomen triangular, telson with concave lateral margins, rounded tip (Fig. 2 C); G1 generally slender, straight with bifurcated distal segment (Fig. 2 D, 3B, C); basal segment of G2 subquadrate (Fig. 3 A).
Etymology. The genus name is derived from the Chinese word for West Canton, Yue Xi, which is the type locality. The suffix potamon refers to the type genus of the Potamidae family, Potamon. Gender of genus neuter.
Remarks. Although Huananpotamon and Yuexipotamon, new genus, are superficially similar, Yuexipotamon, new genus, can easily be distinguished from by a large number of characters (Table 1).
Comparative material. Huananpotamon chongrenense Dai, Zhou & Peng, 1995: holotype male (AS-CB 05123), Chongren County, Jiangxi Province, China, October, 1989 [photographs examined]; Huananpotamon lichuanense Dai, Zhou & Peng, 1995: holotype male (AS-CB 05116), Lichuan County, Jiangxi Province, China, July, 1980 [photographs examined]; Huananpotamon ruijinense Dai, Zhou & Peng, 1995: holotype male (AS-CB 05123), Baying County, Ruijin City, Jiangxi Province, China, October, 1989 [photographs examined]; Nanhaipotamon guangdongense Dai, 1997: 1 male (36.2 × 28.4 mm) (SYSU 001003), Zhuhai, Guangdong, China, coll. C. Huang, February 2011, 1 male (30.5 × 24.3 mm) (SYSU 001004), Zhuhai, Guangdong, China, coll. C. Huang, August 2012.
Yuexipotamon arcophallus, new species (Figs. 1–5)
Material examined. Holotype: male (21.7 × 18.1 mm) (SYSU 001005), Zhaoqing, Guangdong, China, shallow creek, among detritus, coll. J.Y. Li, May 2012. Paratypes: 1 female (allotype) (16.7 × 12.9 mm) (SYSU 001006), Zhaoqing, Guangdong, China, water-logged forest floor, mud burrow, coll. C. Huang, March 2013; 3 males (19.6 × 17.2 mm, 21.6 × 18.1 mm, 18.6 × 15.1 mm) (SYSU 001007–001009), same data as allotype; 1 male (19.78 × 15.55 mm) (ZRC 2013. 1807), same data as allotype; 1 female (18.3 × 14.2 mm) (ZRC 2013. 1807), same data as allotype; Others: 2 males (14.8 × 11.7 mm, 13.1 × 10.4 mm) (SYSU 001010–001011), same data as allotype; 2 females (14.6 × 11.7 mm, 9.7 × 7.9 mm) (SYSU 001012–001013), same data as allotype.
Diagnosis. As for genus.
Description. Carapace subquadrate; dorsal surface slightly convex transversely, longitudinally; surface covered with fused rugae on anterolateral region (Fig. 2 A). Front slightly deflexed, margin ridged on dorsal view (Fig. 2 A). Epigastric cristae low, separated by narrow gap (Fig. 2 A, B). Postorbital cristae sharp, laterally expanded, not fused with epigastric cristae or reach the anterolateral margin (Fig. 2 A, B). Branchial regions relatively flat (Fig. 2 A). Cervical groove shallow, inconspicuous (Fig. 2 A). Mesogastric region slightly convex (Fig. 2 A). External orbital angle bluntly triangular (Fig. 2 A). Epibranchial tooth small, granular, but distinct (Fig. 2 A, B). Anterolateral margin distinctly cristate, lined with approximately 22–25 granules; lateral part bent inwards (Fig. 2 A). Posterolateral margin comparatively smooth, lined with multiple oblique striae, converging towards posterior carapace margin (Fig. 2 A). Orbits large; supraorbital and infraorbital margins cristate, lined with numerous inconspicuous granules (Fig. 2 B). Sub-orbital, sub-hepatic and upper parts of pterygostomial regions covered with large rounded granules (Fig. 2 B). Third maxilliped with merus about 1.1 times as broad as long; ischium about 1.5 times as long as broad; merus trapezoidal, with median depression; ischium trapezoidal, with distinct median sulcus; exopod reaching to proximal third of merus, with short flagellum reaching proximal twofifths width of merus; upper-inner margin of ischium forming subauriculiform structure (Fig. 2 B, 3D). Posterior margin of epistome narrow; median lobe broadly triangular, lateral margins almost straight (Fig. 2 B).
Chelipeds unequal (Fig. 2 A). Merus cross-section trigonal; margins crenulated, dorsal-outer surface granulated (Fig. 2 B). Carpus with sharp spine at inner-distal angle, spinule at base, inner-dorsal surface with curved striae (Fig. 2 A). Palm of larger chela about 1.3 times as long as high. Movable finger equal to fixed finger (Fig. 2 A). Inner margin of fingers with rounded, blunt teeth; with small gap when closed.
Ambulatory legs slender, with dense short setae on dactylus and propodus, relatively sparse short setae on carpus, merus (Fig. 2 A). Last leg with propodus about 2 times as long as board, approximately same length as dactylus (Fig. 2 A).
Thoracic sternum generally smooth, weakly pitted; sternites 1, 2 completely fused to form triangular structure; sternites 3, 4 fused with slightly sinuous median suture; male sterno-abdominal cavity reaching to imaginary line joining median part of coxae of cheliped; median longitudinal groove between sternites 7, 8 deep (Fig. 2 C, 4C).
Male abdomen triangular; somites 3–6 progressively broader longitudinally; somite 6 about 1.8 times as board as long; telson about 1.1 times as board as long with a rounded tip, lateral margins of telson slightly concave (Fig. 2 C).
G1 slender, inner margin of terminal segment notably arched, strongly concave; tip of terminal segment reaches beyond suture between sternites 5, 6, approaches but does not reach tubercle lock of abdominal locking structure in situ; distal part of subterminal segment relatively broader than terminal segment; subterminal segment about 2.2 times as long as terminal segment; terminal segment distinctly elongate, bifurcated at inner-distal part, outer-distal angle triangular, pointing inwards and upwards, respectively (Fig. 2 D, 3B, C, 4A, B, 5A–D). G2 basal segment about 2.2 times length of flagelliform distal segment (Fig. 3 A).
Variation. Overall, there is not much morphological variation in the carapace. The inner-distal angle of the G 1 may vary in the direction it points and the outer-distal angle can vary in sharpness. However, the overall shape of the inner margin and the bifurcated structure of the distal region of the terminal segment are consistent features. (Fig. 5)
Etymology. The name arcophallus is derived from the arc-like terminal segment of the G1.
Colour. Generally dark brown to purplish brown in life. (Fig. 1 A)
Ecology. The type locality, Heishiding Nature Reserve, is located between 23°25'15” – 23°30'02”N, 111°49'09” – 111°55'01”E, and covers an area of 4200 hectares. The locality consists of tropical/sub-tropical evergreen broad-leaved forest with many mountain streams. Yuexipotamon arcophallus, new genus, new species, lives in small hill streams or waterlogged forest floors. They are primarily aquatic and can be found residing under rocks or in burrows during the day. The burrows are usually “Y” shaped with two exits (Fig.1 B). In their natural habitat, they occur sympatrically with the potamids Chinapotamon depressum Dai, Song, Li & Liang, 1980, and Nanhaipotamon cf. pingyuanense Dai, 1997. Being the smallest of the three species found in the reserve, Yuexipotamon arcophallus, new genus, new species, is likely preyed upon by the other larger potamid species. This may be a reason to why they are most abundant in very shallow creeks and waterlogged forest floors where the water is not deep enough for the large Chinapotamon depressum and away from the burrows of Nanhaipotamon cf. pingyuanense.
description: Published as part of Huang, Chao, Mao, Si Ying & Huang, Jian Rong, 2014, Two new potamid crabs, Yuexipotamon arcophallus new genus, new species and Minutomon shanweiense new genus, new species, (Crustacea: Decapoda: Brachyura: Potamidae) from southern China, pp. 455-466 in Zootaxa 3764 (4) on pages 455-461, DOI: 10.11646/zootaxa.3764.4.5, http://zenodo.org/record/231168