Parasesarma De Man, 1895

Ng, Peter K. L., Davie, Peter J. F. & Li, Jheng-Jhang, 2016, On the identities of Parasesarma carolinense (Rathbun, 1907) and Parasesarma sigillatum (Tweedie, 1950), with description of a new species from Taiwan (Crustacea: Brachyura: Sesarmidae), Raffles Bulletin of Zoology 64, pp. 257-268 : 257

Parasesarma De Man, 1895

Type species. Cancer quadratus Fabricius, 1798 ; subsequent designation by Rathbun (1918).

Remarks. Parasesarma De Man, 1895 , is one of the largest genera in the Sesarmidae , with 38 recognised species ( Ng et al., 2008; Rahayu & Ng, 2009, 2010; Davie & Pabriks, 2010; Naderloo & Schubart, 2010; Rahayu & Li, 2013). Parasesarma carolinense and P. sigillatum belong to a group of species that have relatively short ambulatory legs, with the meri transversely broad; and the meri and propodi of the second leg less than three times as long as wide (cf. Rahayu & Ng, 2009); and are unique in having the distal margin of their cheliped merus expanded into a lamelliform structure with distinct spination. A third species from Taiwan, P. corallicum n. sp., is recognised here. The three species also share the following features: small adult size (mature at carapace widths of 7–8 mm); a trapezoidal carapace in which the lateral margins are strongly convergent towards the posterior carapace margin; the dorsal pectinate ridges on the palm are short; the inner surface of the chela has a transverse granulated ridge; the dorsal margin of the dactylus of the cheliped has about 16 triangular tubercles; and the tips of the fingers are excavated on the inner face. The two species freshly collected for this study ( P. sigillatum and P. corallicum n. sp.) also do not appear to be dependent on mangrove habitats, as is typical of most Parasesarma species. They occur, instead, in relatively exposed supralittoral habitats on coral atolls, usually under debris or among rocks. The habitat of P. carolinense in the Caroline Islands is not known, but we believe it is likely to be similar.