David Krause first tentatively referred to the species P. cf. carvus in 1980, and then gave it its current classification in 1987.

The tentatively referred material of this species from Pakistan includes a single M2.

An additional specimen, tentatively referred to H. ferrieri was described in 1955.

It was originally tentatively referred to P. torminni by Praderio et al. (2009).

This species was first tentatively referred to as P. cf. carvus, (Krause, 1980).

It is also within the suborder "Plagiaulacida" and has been tentatively referred to the family Eobaataridae, though it probably is not a member.

At this time, it was tentatively referred to as Midwest Christian Junior College.

Although the genus was first named in 1940, material from one species, E. yakovlevi, was originally tentatively referred to Trematosuchus in 1926.

A fourth fossil found in 1999, IVPP V12756 consisting of foot bones, was tentatively referred to the species.

However, these remains have never been fully described or illustrated and are only tentatively referred to Ammosaurus.