On the family Caridionidae fam. nov., with the description of a new species from the Mediterranean Sea (Crustacea: Decapoda)

Abstract

The hippolytoid shrimp genus Caridion has long had an uncertain systematic position and traditionally has been assigned to Hippolytidae despite the currently perceived non-monophyly of that family. Until now, the genus included two recognised species, C. gordoni and C. steveni , both known from North Atlantic waters, whereas several larval and adult records from the Mediterranean Sea have remained taxonomically unresolved. Here, we describe a new species of Caridion from the western Mediterranean. The new species differs from its congeners by the shape and dentition of the rostrum, the relative length of the third maxilliped, the gill formula, the colour pattern, and its cave-associated ecology. Based on a phylogenetic analysis of four gene fragments, Caridion is recovered outside Hippolytidae and Thoridae, and a new monotypic family, Caridionidae, is established to accommodate the genus. Although uncommon, Caridion epitelum sp. nov. appears to be widespread at least in the western Mediterranean. It has remained undescribed to date because of its cryptic habitat, general taxonomic confusion in the genus and potentially its general resemblance, at least in situ , to common Mediterranean cave-dwelling shrimp, such as Lysmata nilita .