Geothelphusa shernshan, Chen & Cheng & Jhy-Yun & Shy, 2005

Chen, Wen-Jou, Cheng, Jin-Hua, Jhy-Yun & Shy, 2005, On Two New Species Of Freshwater Crabs (Crustacea: Decapoda: Brachyura: Potamidae) From Southern Taiwan, Raffles Bulletin of Zoology 53 (1), pp. 103-110 : 104

Geothelphusa shernshan , new species

( Figs. 2A, B , 5 )

Material examined. – Holotype - male (29.5 by 22.5mm) ( NTOU F000101 ), Wutai, Pingtung county, coll. W.J. Chen, C.F. Tseng & C.Y. Lian, 2 Feb.2000.

Paratypes – 1 male (31.4 by 23.5 mm), 1 female ( NTOU F000201 ), same data as holotype ; 2 males, 2 females (larger female 30.6 by 23.2 mm) ( NTOU F001001 ), Wutai , Pingtung county, coll. W.J. Chen & C.F. Tseng, 7 Oct. 2000 ; 3 males (larger male 24.3 by 18.5 mm) ( NTOU F011201 ), Wutai , Pingtung county, coll. W.J. Chen, 2 Dec. 2001 .

Diagnosis. – Carapace with some fine pits, width and length about 2.2 and 1.7 times depth; width about 1.3 times length; frontal width about 0.3 times carapace width (Table 1). Gastric region smooth, anterolateral region, epigastric region and branchial regions swollen. Postorbital cristae faint, orbital and frontal regions distinctly concaved, divided into 2 lobes. Anterolateral crista distinct, epibranchial tooth almost absent. Cervical groove shallow, faint. H-shaped gastric groove very distinct. Posterolateral margin broadly rounded, with several shortly, transverse fine striae. Posterior epistomal margin sinuous, median lobe acutely triangular( Fig.2A ).

Abdomens of male and female with 7 distinct segments (including telson); in male, length of telson 0.6 times width, longer than 6th, as in female (Table 2). Distance between tip of male abdomen and anterior margin of thoracic sternite 4 about 2 times of that between sternites 1-3.

Chelipeds unequal, in large chela, outer surface of palm smooth, upper margin length 0.6 times length of dactylus, height 0.5 times length of chela (Table 3). Length of dactylus 0.7 times that of chela. Fingers with obliquely triangular gape when closed, without conspicuous cutting teeth. Carpus of large chela with 1 large spine on inner-upper surface and a small one below it. Inner surface of merus of chelipeds glabrous, outer surface with fine striae.

Ambulatory legs slender, glabrous, except dactylus and propodus; second longest, last shortest. In last 2 segments of right second ambulatory leg, width of propodus 0.4 times length, 0.3 times length of dactylus length; length of propodus 0.9 times dactylus length (Table 4). Dactylus with a row of

4-9 spines on each of 4 longitudinal margins, propodus with 2 ventral rows of 4-6 spines.

G1 slender ( Fig. 5 ). Subterminal segment curved outwards at base; outer proximal margin with tooth, inner proximal margin dilated, both proximal margins with plumose setae, prominently on inner proximal margin. Terminal segment of G1 straight, slightly curved upwards, distal scales are sparsely distributed and has 2-3 rings of small spines ( Fig. 3A ). Total length of G1 5.4 times of terminal segment length, 3.4 times subterminal segment width. Terminal segment length of G1 2.6 times width, synovial membrane length 3.7 times width ( Figs. 3D , 5C ). Basal segment of G2 broad. Distal segment of G2 straight, flat, directed upwards, length 0.2 times of total G2 length ( Fig. 5D ).

Coloration. – Carapace dark brown, with upper surfaces of ambulatory legs, subhepatic region light brown. Fingers of chelipeds and abdomen whitish, sometimes orange, with all joints of ambulatory legs and chelipeds usually yellowishorange ( Figs. 2A, B ).

Habitat. – Lives in shallow burrows under boulders near stream.

Etymology. – The species is named after its type locality and the name is used as a noun in apposition.

Remarks. – With regards to the adult body size, colour type, distribution, and general G1 form, G. shernshan is perhaps closest to G. neipu Chen, Cheng & Shy, 1998 . However, these two species can easily be distinguished in the form of the G1 terminal segment. In G. shernshan ( Figs. 3A, D ), the G1 terminal segment distal scales are more sparsely distributed than in G. neipu ( Fig. 3B, E ); in G. shernshan , the total length of the G1 is 5.4 times the terminal segment length, but is 7 times in G. neipu ( Shy et al., 2000:148) ; and in G. shernshan , the length of the G1 terminal segment is 2.6 times the width, but only 1.9 times of that in G. neipu ( Shy et al., 2000:148) . Although G. neipu is also closely allied to G. pingtung Tan & Liu, 1998 ( Shy et al., 2000:149; Ng et al., 2001), we can distinguish G. pingtung , G. neipu and G. shernshan easily when mature males (cw> 30.0 mm) are available. In G. neipu , the G1 terminal segment distal scales are more sparsely distributed than in G. pingtun ( Fig. 3B, C ). The posterior border of the carapace (pc) of G. pingtung (cw/pc mean SE = 2.8 0.04, n = 5) is also wider than G. neipu (cw/pc mean

SE = 3.0 0.05, n = 5). As such G. pingtung is more quadrate than G. neipu .

Distribution. – Wutai township, Pingtung county, southern Taiwan (present study).

Figures

Fig. 2, A-B: Geothelphusa shernshan, new species. Holotype male, 29.5 by 22.5 mm (NTOU F000101). C-D: G. lili, new species. Holotype male, 20.1 by 15.5 mm (NTOU F000701). A, C: dorsal view; B, D: frontal view.

Fig. 5, Geothelphusa shernshan, new species. Holotype male, 29.5 by 22.5 mm (NTOU F000101). A: carapace; B: ventral view of right G1; C: dorsal view of right G1; D: ventral view of right G2; d: ventral view of right G1 terminal segment. Scale: a – c = 1 mm, d = 0.1 mm, e = 3 mm.

Fig. 3, A, D: Geothelphusa shernshan, new species. Paratype male, 24.3 by 18.5 mm (NTOU F011201). B, E: G. neipu. Paratype male, 34.1 by 26.4 mm (NTOU F001004). C, F: G. pingtung. Paratype male, 35.9 by 28.9 mm (NTOU F001005). All dorsal view of G1, A - C: terminal segment; D - F: synovial membrane. Scale, A = 100 m; B,C = 200 m; D,E = 1 mm; F = 2 mm.