Richerellus, Crosnier, 2003

Crosnier, Alain, 2003, A New Genus And Species Of Portunid Crab (Crustacea: Decapoda: Brachyura) From New Caledonia, South-West Pacific, Raffles Bulletin of Zoology 51 (2), pp. 315-321 : 315-316

Richerellus , new genus

Type Species. – Richerellus moosai , new species. Diagnosis. – Carapace slightly oval transversally, smooth, without well defined regions. Front broad, bilobed, without distinct inner orbital lobes. Anterolateral margins of carapace with four prominent teeth, the posterior ones sharp and slender. Basal antennal segment slender, twice as long as broad. Antennal flagellum entering orbit. Third maxilliped merus slightly longer than wide, with the antero-external angle barely produced. Ocular peduncle short and thick, lacking tubercle on anterodistal border in front of cornea. Chelipeds large, unequal, longer than other pereiopods, lacking pronounced carinae; merus long, bearing 2-4 strong, sharp teeth on anterior border; carpus with 2 spinous teeth; outer surfaces of chelae without teeth. Pereiopods 2-4 slender, long. Pereiopod 5 with propodus and dactylus widened, flat, forming swimming paddle. Male abdomen triangular; third to fifth segments fused. First male pleopod rather stout throughout its length, sinuous, with a slightly bilobed distal part.

Etymology. – The genus is dedicated to Bertrand Richer de Forges (IRD), in recognition of over 20 years of work that immensely improved our knowledge of the marine fauna of the South West Pacific.

Remarks. – Although I classify without hesitation the species described herein in the family Portunidae and think it necessary to create a new genus, Richerellus , for it, the placement of this new genus in one of the present subfamilies of the family Portunidae is less evident.

Amongst the portunid genera, Richerellus seems closest to Carupa . It shares with it the general shape of the carapace, transversally oval, smooth, without pronounced regions and with dentate anterolateral margins; the wide front; the antenna with the basal segment slender, twice as long as broad and a flagellum entering the orbit; the ocular peduncle without tubercle; the general shape and ornamentation of the chelipeds; the slenderness and the length of the second to fourth pereiopods; the paddle-shaped fifth pereiopod; the general shape of the male abdomen; and the first male pleopod remaining rather stout along all its length.

Richerellus differs from Carupa by the bilobed front (instead of quadrilobed), the inner orbital lobes indistinct (instead of faintly distinct), the anterolateral margin of the carapace cut into 4 teeth (instead of 7 teeth); the chelipeds elongated, longer than the other pereiopods, smooth, without pronounced carinae (instead of being shorter than the other pereiopods, stouter and with carinae more pronounced); the second abdominal segment with a carina along all its breadth (instead of uncarinated); the first male pleopod sinuous (instead of straight in its basal part, then regularly curved) and slightly bilobed in its distal part.

On these characters, Richerellus seems to belong to the subfamily Carupinae Paulson, 1875 (see Apel & Spiridonov, 1998: 170), which currently includes three genera Libystes , Catoptrus and Carupa , although these seem too different from one another to be placed in the same subfamily (see Serène, 1966). However this is a difficult question and it is not in our intention to treat it here.