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Origin of Mammals Based Upon Cranial Morphology of the Therapsid Suborders

1944; Geological Society of America; Linguagem: Inglês

10.1130/spe55-p1

2331-219X

Everett C. Olson,

Evolution and Paleontology Studies

Serial sections of skulls of four therapsid suborders, Gorgonopsia, Therocephalia, Anomodontia, and Cynodontia, have provided a basis for detailed studies of the cranial characters of reptiles which are approaching the mammalian threshold. Structures of the inner ear, the middle ear, the occipital region, and the basicranial axis are described in detail for each of the four suborders. Comparisons of the suborders are based on analyses of proportions of the parts of the brain case and the evolution of each part of the skull is traced. These analyses are used as a basis for studies of therapsid phylogeny and the origin...