Reports

Mesozoic Mammals from Arizona: New Evidence on Mammalian Evolution

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Science  16 Dec 1983:
Vol. 222, Issue 4629, pp. 1233-1235
DOI: 10.1126/science.222.4629.1233

Abstract

Knowledge of early mammalian evolution has been based on Old World Late Triassic-Early Jurassic faunas. The discovery of mammalian fossils of approximately equivalent age in the Kayenta Formation of northeastern Arizona gives evidence of greater diversity than known previously. A new taxon documents the development of an angular region of the jaw as a neomorphic process, and represents an intermediate stage in the origin of mammalian jaw musculature.

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