Pteropoda (common name pteropods, from the Greek meaning "wing-foot") are specialized free-swimming pelagic sea snails and sea slugs, marine opisthobranch gastropods. The monophyly of Pteropoda is the subject of a lengthy debate; they have even been considered as paraphyletic with respect to cephalopods. Current consensus, guided by molecular studies, leans towards interpreting the group as monophyletic.