This species is based on UCMP 36058, a complete skull from the Wupatki Member of the Moenkopi Formation in Arizona.

[2][3] Another potential species, Wellesaurus africanus, is from subzone B of the Cynognathus Assemblage Zone in South Africa.

Although this species was originally formulated in 1909, the fragmentary preservation of its material has prevented precise conclusions on its affinities.

As a result, it has been referred to a variety of mastodonsauroid genera, including Capitosaurus, Parotosuchus, and Wellesaurus.

[4] A third potential species, Wellesaurus bussoni, was named in 1971 based on fragmentary skull material from the Lower Sandstone Member of the Zarzaïtine Series in Algeria.