Dinocephalia is a clade of generally large-bodied therapsids that flourished during Middle Permian between approximately 275 and 260 million years ago (Ma), but became extinct during the Capitanian mass extinction event. Dinocephalians included herbivorous, carnivorous, and omnivorous forms. Many species had thickened skulls with many knobs and bony projections. Dinocephalians were the first non-mammalian therapsids to be scientifically described and their fossils are known from Russia, China, Brazil, South Africa, Zimbabwe, and Tanzania.
Description
They include carnivorous, herbivorous, and omnivorous forms. It has been disputed as to whether some dinocephalians were semi-aquatic like hippopotamuses.
Size
Dinocephalians were generally large in size, The herbivorous or omnivorous Jonkeria has been suggested to have weighed , while the large carnivore Anteosaurus has been estimated to weigh based on scaled 3D models.
Skull and jaws
The temporal fenestra at the back of the skull is relatively enlarged in dinocephalians,<sup>11</sup> with the quadrate and quadratojugal bones at the back of the skull also being enlarged. Correlated features are the distinctly downturned facial region, a deep temporal region, and forwardly rotated suspensorium. Shearing contact between the upper and lower teeth (allowing food to be more easily sliced into small bits for digestion) is achieved through keeping a fixed quadrate and a hinge-like movement at the jaw articulation. The lower teeth are inclined forward, and occlusion is achieved by the interlocking of the incisors. The later dinocephalians improved on this system by developing heels on the lingual sides of the incisor teeth that met against one another to form a crushing surface when the jaws were shut.
center|thumb|350x350px|Suggested [[intraspecific combat styles in dinocephalians. 1/top left: Face biting (Anteosauria), 2/top centre: head-butting (Tapinocephalidae e.g. Moschops), 3/ left: flank butting (Styracocephalus) 4/bottom left: locking and pushing (Estemmenosuchus) 5. bottom centre: stabbing (Struthiocephalus)]]
Most dinocephalians also developed a thickened (pachyostotic) and ornamented skull roof and braincase of varying and diverse form, sometimes with horn-like projections.
The coronoid bones and the corresponding coronoid process on the lower jaw were lost in dinocephalians. or a posture intermediate between sprawling and upright.