A new species of Pilumnus Leach, 1816 (Decapoda, Brachyura) from Guadeloupe, Lesser Antilles, with morphological comparisons to regional congeners

Pilumnus Leach, 1861 is a speciose cosmopolitan genus of marine crabs typical from rocky and coral coastal environments and known to occur in tropical and temperate oceans and seas worldwide, including the waters of western Atlantic and Caribbean Sea surrounding the Lesser Antilles, a recognized hotspot of biodiversity in Caribbean. Despite recent sampling efforts, this region remains underexplored, limiting understanding of its marine fauna. To address this gap, several field expeditions have been carried out, including KARUBENTHOS 2012. This expedition extensively collected specimens of various taxonomic groups, expanding documentation of biodiversity in the Lesser Antilles. Among collections, a unique specimen of Pilumnus was recognized and analyzed through morphological and molecular approaches. Genetic analyses of this specimen, a component of molecular phylogenetic studies previously conducted by our team, confirmed its divergence from previously described species. Herein, we performed a thorough morphological examination analyzing most of the taxonomic informative characters used in species descriptions of representatives of Pilumnus. Based on the presently accessed morphological features and previously detected molecular divergence, a new species, Pilumnus guadeloupensis n. sp., is described. This species can be distinguished from others from the genus mainly by the ornamentation and tuberculation patterns of pereopods, number of anterolateral prominences and shape of the carapace. Detailed morphological comparisons with congeners, alongside a comprehensive review of the literature, are provided.