The Teudopseina is a clade of stem-octopods that first evolved in the Toarcian,[1] considered the largest clade of gladius-bearing coleoids in the Mesozoic. Up to five families are known, among which the Trachyteuthidae, Trachyteuthis in particular, were the most abundant.[2]
The Teudopseina can be united by five primary traits. These are the presence of a gladius, a reduced, spoon-shaped conus, a median field that is distinctly rounded or pointed anteriorly, weakly curved hyperbolar zones, and lateral fields shorter than the hyperbolar zones.[2] Members of the superfamily Muensterelloidea are characterized by a spoon-shaped section of the gladius, known as the patella. This is believed to be ancestral to the condition present in modern octopuses.[3]
The current consensus is that the Teudopseina forms a stem-group of the Octopoda.[4] [5] Certain taxa, such as Enchoteuthis, have sometimes been classified as either relatives of giant squids or vampire squids.