It was first described by E. T. Newton in 1894 for remains found in northeastern Scotland, including four specimens from the latest Carnian Lossiemouth Sandstone Formation.

[1] Additional remains of Erpetosuchus have been found in the New Haven Formation of Connecticut in the eastern United States, although they were not attributed to the species E. granti.

[2] Erpetosuchus granti was originally assigned to Thecodontia, but that name is no longer considered valid in scientific literature because it is a paraphyletic group of early archosaurs.

A more recent phylogenetic analysis by Olsen et al. (2000) found E. granti to be the sister-taxon to the Crocodylomorpha.

Nesbitt and Butler (2012) included Erpetosuchus within a more comprehensive phylogenetic analysis and found it to group with the archosaur Parringtonia from the Middle Triassic of Tanzania.