Osteology of the pristerognathid Cynariognathus platyrhinus (Reptilia, Theriodontia)
1967; Cambridge University Press; Volume: 41; Issue: 3 Linguagem: Inglês
ISSN
1937-2337
Autores Tópico(s)Ichthyology and Marine Biology
ResumoThe first known complete skeleton of the primitive mammal-like reptile Cynario- gnathus platyrhinus (Family Pristerognathidae, Infraorder Therocephalia) from the Middle Permian of South Africa shows both primitive and advanced features, the former outnumber- ing the latter. The pectoral girdle, pelvic girdle, astragalus, and calcaneum are all primitive in morphology. The structure of the stapes and vertebrae, well-defined lumbar ribs, and phalangeal formula of 2-3-3-3-3 are all advanced characters. Moreover, some very specialized features occur in Cynariognathus: the strong inward curve of the lower anterior margin of the scapula, the posterior curvature and expanded distal ends of the lumbar ribs, and the disc- shape of the medial phalanges of digits III and IV of the manus. In general, the skeleton is large and robust which implies a cumbersome and slow-moving living animal. Cynariognathus had a mammal-like posture with the legs under the body as in advanced therapsids in general. The primitive therocephalians are in a position to be the ancestors of all the advanced therocephalians, bauriamorphs, and very probably the cynodonts. However, the aforemen- tioned specializations make it seem unlikely that Cynariognathus itself is on the main thero- cephalian evolutionary line. In both postcranial and cranial morphology the primitive thero- cephalians are more advanced than the contemporaneous gorgonopsians.
Referência(s)