A mesopelagic ctenophore representing a new family, with notes on family-level taxonomy in Ctenophora: Vampyroctena delmarvensis gen. nov. sp. nov. (Vampyroctenidae, fam. nov.)

The stunning diversity of midwater ctenophores is well-known to veterans of oceanographic cruises and ROV operations, but many species lack formal descriptions, leading to taxonomic confusion and a systematic underestimation of the biodiversity of the mesopelagic zone. Here, we present a description of a novel genus and species of one such ctenophore, Vampyroctena delmarvensis gen. nov. sp. nov. This cydippid ctenophore, the sole described representative of Vampyroctenidae fam. nov. (Class Tentaculata, Order Cydippida), was collected in mesopelagic waters off the coast of Delaware in the northwest Atlantic Ocean and has a characteristic bright red mesoglea, large paragastric diverticulae, deep red macrocilia, and a darkly pigmented gut. A molecular phylogenetic analysis of Ctenophora based on transcriptomic data places V. delmarvensis gen. nov. sp. nov. as the closest known relative to Euplokamis dunlapae Mills, 1987 (Euplokamididae), in a clade that is sister to all other ctenophore lineages.