Thelphusula Bott, 1969

Grinang, Jongkar & Ng, Peter K. L., 2014, Taxonomy of the freshwater crab Coccusa cristicervix Ng & Grinang, 2004 (Decapoda: Brachyura: Gecarcinucidae), with description of a new species of Thelphusula from Sarawak, Malaysia, Borneo, Raffles Bulletin of Zoology 62, pp. 389-395 : 389-390

Thelphusula Bott, 1969

Remarks. Thelphusula Bott, 1969 , was established with Potamon (Geothelphusa) buergeri De Man, 1899 , as the type species. Bott (1969) recognised five other species in the genus as he defined it at the time: Potamon (Potamonautes) baramensis De Man, 1902 , Potamon (Geothelphusa) hendersonianum De Man, 1899 , Potamon (Geothelphusa) kadamaianum Borradaile, 1900 , Parathelphusa (Liothelphusa) luidana Chace, 1938 , and Potamon (Potamon) melanippe De Man, 1899 (see also Bott, 1970: 58). Potamon (Thelphusa) bidiensis Lanchester, 1900 , was regarded as a junior subjective synonym of Thelphusula melanippe , while Potamon kadamaianum was treated as its subspecies by Bott (1970). Ng (1989a: 64) questioned Bott’s (1970) concept of Thelphusula and argued that it should be separated into three distinct morphological groups. He disputed Bott’s (1970) synonymisation of Potamon bidiensis with T. melanippe ; recognised it as a distinct species and referred it to a monotypic genus, Stygothelphusa Ng, 1989a . Ng (1991) subsequently established a new genus, Arachnothelphusa , for Potamon (Potamon) melanippe De Man, 1899 , and Potamon (Geothelphusa) kadamaianum Borradaile, 1900 , treating both as distinct species. Ng (1995), in describing a new genus from western Sarawak, showed that Potamon (Geothelphusa) hendersonianum De Man, 1899 , had been incorrectly placed in Thelphusula as it has differently structured G1 and G2, and should be transferred to Bakousa Ng, 1995 , instead. Tan & Ng (1998) revised Thelphusula , restricted the diagnosis for nine species and established a new genus, Coccusa , for two species from Borneo in which the carapace is ovate and much smoother, and most significantly, the G1 terminal segment is very long, slender and as long as the subterminal segment (versus distinctly shorter than the subterminal segment in Thelphusula s. str.).

Ng & Grinang (2004) recognised a third species of Coccusa from western Sarawak. Although only one adult female specimen was available, they noted that the general carapace shape and features agreed better with Coccusa and therefore referred it to this genus, even though it was the most granulated of the three known taxa. The collection of more specimens of the Sarawakian species, including males, shows that Coccusa should be restricted for species with smoother carapaces. On the basis of the gonopod structures, Coccusa cristicervix Ng & Grinang, 2004 , must be transferred to Thelphusula instead.