Dinocephalians retain a number of primitive characteristics (e.g. no
secondary palate, small
dentary) shared with their
pelycosaur ancestors, although they are also more advanced in possessing therapsid adaptations like the expansion of the
ilium and more erect limbs. 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,
Skull ,'' showing cranial ornamentation All dinocephalians are characterised by the interlocking incisor (front) teeth, though this was formerly thought to be unique to the group, it is also found in
biarmosuchians. 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. Most dinocephalians also developed a thickened (
pachyostotic) and ornamented skull roof, sometimes with horn-like projections, with the tapinocephalids suggested to have engaged in
head-butting. == Evolutionary history ==