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Science 1 May 1970:
Vol. 168. no. 3931, pp. 573 - 575
DOI: 10.1126/science.168.3931.573
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Articles

Dentary-Squamosal Joint and the Origin of Mammals

Herbert R. Barghusen 1 and James A. Hopson 2

1 Departments of Anatomy and Oral Anatomy, University of Illinois Medical Center, Chicago 60680
2 Department of Anatomy, University of Chicago, Chlicago, Illinois 60637

The dentary-squamosal jaw joint evolved more than once in advanced cynodont therapsids or their descendants, probably as a buttress against the reaction force created at the articulation by the adductor jaw musculature. The multiple origin of this joint suggests that additional criteria are required to separate early mammals from advanced therapsids.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)