Nature 358, 233 - 235 (16 July 1992); doi:10.1038/358233a0

Post-Jurassic mammal-like reptile from the Palaeocene

Richard C. Fox^*†, Gordon P. Youzwyshyn^* & David W. Krause^‡

^*Laboratory for Vertebrate Paleontology, Departments of Geology and Zoology, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
^‡Department of Anatomical Sciences, State University of New York, Stony Brook, New York 11794-8081, USA
^†To whom correspondence should be addressed

MAMMAL-LIKE reptiles of the Order Therapsida document the emergence of mammals from more primitive synapsids¹ and are of unique zoological and palaeontological interest on that account². Therapsids, first appearing in the Early Permian³, were thought to become extinct in the Middle Jurassic^4,5, soon after the Late Triassic origin of mammals⁶. Here, however, we report the discovery of a therapsid from the late Palaeocene, 100 million years younger⁷ than the youngest previous occurrence of the order. This discovery nearly doubles the stratigraphic range of therapsids and furnishes their first record from the Cenozoic. The documenting fossils, an incomplete dentary containing three teeth, and four isolated teeth from other, conspecific individuals (Fig. 1), are from the Paskapoo Formation, at Cochrane, Alberta, Canada, from beds yielding a diverse mammalian fauna of early Tiffanian age⁸. These specimens are catalogued in the collections of the University of Alberta Laboratory for Vertebrate Paleontology (UALVP) and provide the basis for a new taxon, as named and described below.

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