Estemmenosuchus had a sprawling posture and could reach a body length of more than 3 m (10 ft). Its skull was long and massive, up to 65 cm (26 in) in length, and possessed several sets of large horns, somewhat similar to the antlers of a moose, growing upward and outward from the sides and top of the head.
The skull superficially resembles that of Styracocephalus, but the "horns" are formed from different bones; in Estemmenosuchus the horns are located on the frontals and protrude upward, whereas in Styracocephalus the horns are formed by the tabular and extend aft.
Estemmenosuchus lived some 267 million years ago. Two species have been identified, from the Ezhovo place near Ochyor in the Perm region of the Russia in 1960. They differ in size, shape of the skull, and shape of the horns.
Estemmenosuchus uralensis ("Crowned Crocodile of the Ural Mountains") is the second most primitive therapsid after the Biarmosuchia. The species was found with the Biarmosuchians Eotitanosuchus olsoni and Biarmosuchus tener and with Estemmenosuchus mirabilis in channel flood deposits of the young Ural Mountains.
The species are characterised by horns which project upward and outward on the side of the head. The mouth contained large canines with small molar teeth. The animal had a sprawling posture as indicated by analysing its shoulder joints.
It has been suggested that the animal had a fairly constant internal temperature. Its large size and compact build gave a small surface to volume rate and suggests it would not gain (or lose) temperature quickly. This phenomenon is called gigantothermy and was probably an important factor in temperature regulation in most therapsids. But other scientist believe it was cold blooded, similar to today's reptiles. It has been also suggested that it was a carnivore, but the majority opinion at present is that Estemmenosuchus was a herbivore.
Unlike Estemmenosuchus uralensis, which had only one horn on each side of its head, this species had 2 projecting bony knobs on each side of the cranium, one on the top pointing up looking like antlers and another pointing to the side similar to E. uralensis. Its snout is smaller and wider than its relative and looks vaguely like a modern moose. The palate teeth include six incisors, two canines and about twenty small incisor-like teeth at the rear. The lower palate contained six incisors, two canines and about thirty smaller back teeth.
There were many complete and incomplete skeletons found together.