late early to later Middle Permian Period
Upland terrestrial herbivores
The caseids were a widespread and diverse group of herbivorous pelycosaurs, which 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 massively built 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, seems 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 relatively 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 parelasaurs.
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. There is reduction in the phalangeal formula, ranging from 2-3-4-4-3 to 2-2-2-3-2. In Corylorhynchus the claw bearing element is very large and broad, with apparently sharp edges on the sides. While in Angelosaurus the claw bearing phalanges are also massive, but more conservative in morphology, roughly triangular in outline. This may indicate adaptations to different types of terraine.
|Technical Diagnosis of this family|
Caseidae - genera
Biology 356 - Major Features of Vertebrate Evolution - Permo-Carboniferous Synapsids - by Dr. Robert Reisz, University of Toronto
Caseidae - Palaeos - incorporating Toby White's Vertebrate Notes and material from these pages
Romer, A.S. and Price, L.I. Review of the Pelycosauria, Geological Society of America Special Papers,. no.28,
Robert R. Reisz, Pelycosauria, Encylopedia of Paleoherpetology, Part 17A, 1986, Gustav Fischer Verlag, Stuttgart and New York
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