Represented by a skeleton of a juvenile individual and the skull of an adult primitive, herbivorous reptile, in the family Caseidae.

Although large numbers of individuals of this species have been found concentrated in a sandstone layer at the Pinega Locality, no other species occur there.
Accumulations of numerous individuals of a single species suggest that a group of animals living together were killed by a single event. The site where these fossils occurred is thought to have been a beach of a very large island at the time the animals were alive.

Ennatosaurus tecton was not a therapsid like all of the other mammal-like reptiles on display in this exhibition. Rather, it was an herbivorous member of the pelycosaurs, the more primitive group of mammal-like reptiles out of which the therapsids evolved.