neither is found in true oegopsids. The Bathyteuthida do share the open ocean pelagic habitat with the oegopsid squid, uniting them in that way with that diverse group.

The Bathyteuthidae and Chtenopterygidae differ in body conformation, the internal shell, and in the manner in which buccal supports attach to the lowermost arms (pair IV). Buccal supports attach to the dorsal side of arms IV in the Bathyteuthidae and the ventral side of arms IV in the Chtenopterygidae.