Systematics, distribution and biology of the cirrate octopods of the genus Opisthoteuthis (Mollusca, Cephalopoda) in the Atlantic Ocean, with description of two new species

The systematics of the deep-sea cirrate octopod genus Opisthoteuthis Verrill in the Atlantic Ocean is reviewed. Comparisons, based on examination of all extant type material and new, reported and unreported material collected in recent years from the Atlantic, show the presence of five species: Opisthoteuthis agassizii Verrill 1883, O. grimaldii (Joubin, 1903), O. massyae (Grimpe, 1920) and two new species, O. calypso and O. hardyi, which are described. Opisthoteuthis agassizii, distributed only in the western North Atlantic, is redescribed, and a neotype is designated for the presumed lost holotype. Opisthoteuthis grimaldii, distributed in the East Atlantic and possibly also in the western North Atlantic, and O. massyae, distributed in the East Atlantic are also redescribed and junior synonyms listed. Opisthoteuthis calypso, found in the East Atlantic and O. hardyi, known only from a single specimen from the SW Atlantic are described. New morphometric data for O. agassizii, O. massyae and O. grimaldii are given. Illustrations, geographical distributions and a review of the biological information for all five species are provided.