Get a printable copy pdf file of the complete article 457k, or click on a page image below to browse page by page. Though lowly in origin, but unique in their endowments, they constituted the mammals. The therapsids, members of the subclass synapsida sometimes called the mammal like reptiles, generally were unimpressive in relation to other reptiles of their time. The origin and early radiation of the therapsid mammallike reptiles. The mammals arose from advanced synapsids in the upper triassic, at which time the dinosaur reptiles were rapidly replacing the mammallike reptiles as the principal terrestrial forms. The mammallike reptiles the american biology teacher. The mammallike reptiles of south africa and the origin of. The evolution of mammals has passed through many stages since the first appearance of their. Mammallike reptiles and the origin of mammals, systematic biology, volume 31, issue 4, 1 december 1982.
The orthodox view 1,2 of the ancestry of this important stage in vertebrate history is that the synapsids arose from a hypothetical stemreptile. The first major adaptive radiation of reptiles consisted of the synapsida, or mammallike reptiles, which are now totally extinct, but which dominated the terrestrial fauna from the late pennsylvania, throughout the permian and for much of the triassic periods. The origin of mammals from advanced mammallike reptiles therapsids toward the end of the triassic is now well established on the basis of the fossil record. Throughout the permian period, the synapsids included the dominant carnivores and several important herbivores. The origin and early radiation of the therapsid mammal. Mammallike reptiles and the origin of mammals systematic. This does not include the mammallike reptiles, a group more closely related to the. C, medial view of the jaw in a fetal mammal to show the developmental parallels of. The mammals arose from advanced synapsids in the upper triassic, at which time the dinosaur reptiles were rapidly replacing the mammallike.
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