Phylogeny of the fascinating and frustrating Peracarida: the past, the present and the future

Peracarida (Arthropoda: Crustacea) is one of Earth’s most strikingly diverse animal groups. Often compared with their relatives, the decapods (crabs, shrimp, and lobsters), a better comparison would be with the hyperdiverse insects: small bodies, exceptional diversity of form, and pervasive habitat occupancy. Those traits, and that most live in the challenging ocean environment, have left the peracarids woefully underexplored. Each of the world’s few peracarid taxonomists has an extensive backlog of new species waiting to be described, and every field trip that targets peracarids yields novel species – the scope for diversity discovery is nearly unlimited. The historically sparse diversity sampling has left our understanding of peracarid relationships in a murky state. Making sense of the group’s diversity requires a solid phylogenetic framework to explain their evolutionary history. Here we summarize the 180 years of peracarid history with references to all key taxonomic discoveries and hypotheses. Beyond bringing a historical perspective to the group, we propose phylogenomic approaches to deciphering peracarid phylogeny enabled by current international projects. We welcome collaboration with all researchers working on Peracarida and are particularly interested in partnerships that broaden taxon sampling, expand geographic and habitat coverage, and support opportunities and training for the next generation of peracarid researchers.