It is so far only known definitely from one specimen, a skeleton collected from sandstone of the Upper Jurassic-age Morrison Formation rocks at Dinosaur National Monument, Utah, during road construction.

It is the basalmost crocodyliform of the Morrison Formation, as suggested by such attributes as still having antorbital fenestrae in the skull.

[1] Charles W. Gilmore named Hoplosuchus in 1926; the type species is H. kayi.

[3] A potential second specimen has been recovered from the Morrison Formation of northeastern Arizona; this individual would have been about 50 centimetres (20 in), but the skull is poorly preserved, leaving the identity of the animal unknown.

[1] A 2017 cladistic analysis of Cassissuchus recovered it as a member of Protosuchidae.