A new species of the crab genus Cosmonotus Adams & White in White, 1848, Cosmonotus mclaughlinae n. sp., is described from the Indo-West Pacific Ocean. This new species inhabits coarse sand and shell bottoms between 75 and 369 m and is so far known from La Réunion, Philippines, Indonesia (Kai Islands), Salomon, Futuna, Vanuatu, Loyalty Islands (Lifou), Fiji, Tonga (N Ha’apai Group). This new species is morphologically close to C. genkaiae Takeda & Miyake, 1970, from which it is easily separated by: 1) the carapace covered by squamiform tubercles (instead of long striae); 2) the lack of the median rostral process (instead of being present and short); 3) the dorsal carpal face of chelipeds with rounded tubercles (instead of striae); and 4) the slender, eyestalks (instead of stout).
Crustacea, Decapoda, Brachyura, Podotremata, Raninidae, Cosmonotus, Indo-West Pacific Ocean, new species.