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Synapsid Evolution and the Radiation of Non-Eutherian Mammals

Published online by Cambridge University Press:  17 July 2017

James A. Hopson*
Affiliation:
Department of Organismal, Biology and Anatomy, University of Chicago, 1025 East 57th Street, Chicago, Illinois 60637

Extract

The Synapsida is the mammal-like ramus of the Amniota, the sister group of the Sauropsida (or Reptilia of Gauthier et al., 1988). Synapsids are characterized by the possession of a lateral temporal fenestra (Fig. 1A), among other features (see Gauthier, this volume). Of all the great transitions between major structural grades within vertebrates, the transition from basal amniotes to basal mammals is represented by the most complete and continuous fossil record, extending from the Middle Pennsylvanian to the Late Triassic and spanning some 75 to 100 million years. Structural evolution of particular functional systems has been well investigated, notably the feeding mechanism (Barghusen, 1968; Crompton, 1972; Crompton and Parker, 1978; Crompton and Hylander, 1986) and the middle ear (Hopson, 1966; Allin, 1975, 1986; Allin and Hopson, 1992), and these studies have demonstrated the gradual nature of these major adaptive modifications.

Type
Research Article
Copyright
Copyright © 1994 Paleontological Society 

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