Caseasauria

The caseids were a widespread and diverse group of herbivorous pelycosaurs, they appeared during the later Early Permian and persisted until the late Middle Permian. Although ranging in size from 1 to 6 meters in body length, caseids are surprisingly conservative in their skeletal anatomy and body proportions. All were large-sized animals with small heads and barrel-like bodies. Animals like Angelosaurus and Cotylorhynchus, which exceeded 4 meters in length and were the largest of the pelycosaurs, and they seemed to have played the same ecological role during the later early Permian that the pareiasaurs and herbivorous dinocephalians did during the Middle and Late Permian. Caseids and eothyridids share a number of specialised features associated with the morphology of the snout and external naris and it is likely that the latter evolved from the former. The two together form the clade Caseasauria.

The caseid skull is distinctive in the presence of large temporal openings, enormous external nares (nostril openings, probably to house some kind of sensory or moisture-conserving organ), and large pineal opening, and a snout or upper jaw that dramatically overhangs the tooth row to form a forward projecting rostrum. The external surface of the skull is skulpted with rounded deep pits and sometimes crevice-like depressions. The marginal teeth are quite similiar to the teeth of pareiasaurs.

In contrast to most other pelycosaurs, except Edaphosaurus, and as befits the herbivorous lifestyle, the teeth are remarkably uniform. There is a general reduction in the number of marginal teeth cheek teeth. All caseids, whether modest in size, or enormous, are characterized by small cervical vertebrae, bulky, barrel-shaped bodies and relatively massive limbs.