Discovery of a New Species Provides a Deeper Insight into Taxonomic Grouping of the Deep-Sea Genus Acanthephyra (Crustacea: Decapoda) †

Abstract

We describe and diagnose a new species of Acanthephyra (Acanthephyridae: Caridea: Decapoda) and provide an amended key to all species of the genus. In order to assess the taxonomic position of the new species, we examined and coded 55 characters in available specimens of Acanthephyra and ran morphological phylogenetic analyses. We also used a COI gene marker for molecular analyses of the new species and other available specimens of Acanthephyra. Both analyses retrieved an unexpected grouping of species that contradicted a recently accepted morphological grouping. We tested a new, quantitative, set of characters and found that three of them may explain the molecular grouping of the genus. These characters are linked to: (1) proportions of the 6th pleonic somite, (2) length of the same against carapace length, and (3) length of the same against length of two preceding somites. We suggest that these characters mirror evolutionary traits in Acanthephyra and discuss their possible adaptive sense.