Only three genera are known, Eothyris, Vaughnictis and Oedaleops, all from the early Permian of North America.

Their main distinguishing feature is the large caniniform tooth in front of the maxilla.

Eothyridids share with the Caseidae a number of specialised features associated with the morphology of the snout and external naris and it is likely that their common ancestor was close in build to Eothyris.

Vaughnictis is known from a partial skull, six dorsal vertebrae and some hind-limb bones.

The species were found in the lower Permian in what is today North America.