The diversity and phylogeny of deep-sea Delectopecten scallops are poorly known. We describe Delectopecten thermus sp. nov. from the Higashi–Ensei vent field through morphological, mitogenomic and phylogenetic analyses. Our findings indicate that Delectopecten is monophyletic representing an early diverging pectinid clade, with significant gene-order divergences in mitogenome, but asymbiotic with chemoautotrophs. These results enhance our understanding of the biodiversity of Delectopecten, clarify the phylogenetic relationships within the genus, and provide insights into the trophic patterns of deep-sea scallops. (Image credit: Yi-Tao Lin.)

Annelids are increasingly being found to comprise a substantial fraction of cryptic biodiversity. Perinereis cultrifera is commonly used as a model species, but the possibility of unreported and undescribed cryptic species may compromise the accuracy and interpretation of results. In this study, integrative taxonomy revealed overlooked morphological traits and 18 different European Perinereis lineages (13 of which are formally described) yielding new molecular and taxonomic data available to a range of efforts including metabarcoding, species identification, conservation and biomonitoring. (Image credit: Joachim Langeneck.)