It is known from a single species, Westlothiana lizziae.

It is known from a single species, Ustia atra, which was described in 2003 from an isolated lower jaw.

It is known from a single species, Biarmosuchus tener, and belongs to the monotypic family Biarmosuchidae.

Resting cysts are known from a few species.

It is known from a single species, Cynognathus crateronotus.

It is known from a single species, Intasuchus silvicola, which was named in 1956.

It is known from a single species, Feeserpeton oklahomensis, which was named in 2012 on the basis of a nearly complete skull.

Gnathosaurus (meaning 'jaw lizard') is a genus of ctenochasmatid pterosaur known from a single species, G. subulatus, described in 1833.

It is known from a single species, G. pulcherrimus, although several other species such as G. pustuloglomeratus have been named in the past.

It is known from quite a few species: