Thelphusula pueh Grinang & Ng 2014, new species

Thelphusula pueh, new species

(Figs. 2, 3F–J, 5)

Material examined. Holotype: male (16.2 × 12.1 mm) (ZRC), edge of rice field with swampy vegetation, 26 m above sea level, Kampung Sebako, Pueh, Lundu District, Sarawak, coll. R. Sujang, 29 November 2013. Paratypes: 6 females (12.6–19.8 mm × 9.9–15.6 mm) (ZRC), 4 females (15.8–19.4 mm × 11.4–14.5 mm) (SBC), same data as holotype; 1 female (24.1 × 14.8 mm) (ZRC), in rice field, 31 m above sea level, Kampung Peninjau Lama, Gunung Serambu, Bau District, Sarawak, coll. L. Noun, 10 November 2013.

Diagnosis. Carapace gently ovate, wider than long, dorsal surface rugose, anterolateral margin convex, epibranchial tooth absent, cervical groove relatively shallow, shallow crista; postorbital cristae weak; H-shaped depression shallow (Fig. 2A, B). Frontal margin deflexed; frontal median triangle absent (Fig. 2C). Median tooth on posterior margin of epistome subtruncate (Fig. 2C).Ambulatory legs not distinctly elongated (Fig. 2A). Major chela with large gap between fingers when closed (Fig. 2F). Male abdomen with somite 6 relatively short, lateral margins distinctly concave (Fig. 2D). G1 terminal segment relatively cylindrical, straight, slightly more than 2 times length of subterminal segment (Fig. 3F, H–J). G2 distal segment short, curved, tip rounded (Fig. 3G).

Colour. In life, the species is dark brown overall on all the dorsal surfaces, with the palm of the chela and sometimes the legs more orange (Fig. 5A, B).

Etymology. The species is named after Pueh, the area where it was collected. The name is used as a noun in apposition.

Remarks. Thelphusula cristicervix and T. pueh, new species, are the only two species of Thelphusula known from western Sarawak. They are easily differentiated from congeners in having a relatively more ovate carapace, a more convex anterolateral margin and more strongly deflexed frontal margin. Their G1s are also superficially similar in shape. Thelphusula pueh can most easily be separated from T. cristicervix by its live colours; with the carapace and legs of T. cristicervix red (Fig. 4A, B), even in small specimens, whereas T. pueh is dark brown (Fig. 5A, B). Thelphusula pueh also has proportionately shorter ambulatory legs (Fig. 2A) (versus longer in T. cristicervix, Fig. 1A); relatively shallower cervical grooves (Fig. 2B) (versus distinctly deeper in T. cristicervix, Fig. 1A); smooth lateral margins of abdomen (Fig. 2D) (versus uneven in T. cristicervix, Fig. 1D); and the outer margin of the G1 subterminal segment is almost straight with the terminal segment more strongly bent (Fig. 3F, H) (versus outer margin of G1 subterminal segment gradually curved with the terminal segment gently bent in T. cristicervix, Fig. 3A, C).

Like T. cristicervix, T. pueh has a preference for damp soils and constructs shallow burrows. Its presence in a more open habitat (ricefields) may not be natural.