First taeniodonts (Mammalia, Taeniodonta) from the Paleocene of Canada

Abstract

ABSTRACT The Taeniodonta comprise one of several groups of eutherians that diversified following the extinction of non-avian dinosaurs, and were among the earliest to achieve a relatively large body in the wake of the mass extinction some 66 million years ago. The fossil record of Taeniodonta is sparse, with much of what is known of their evolution being derived from specimens of early Paleocene age from the San Juan Basin of New Mexico. The record is particularly poor at higher latitudes, and while Schowalteria clemensi—the oldest taeniodont, known from but one specimen from southeastern Alberta—lived alongside dinosaurs and a suite of archaic mammals near the end of the Cretaceous, specimens referable to the order have heretofore not been discovered in Paleocene deposits in Canada, despite nearly 60 years of intensive collecting. I report here on the first evidence of taeniodonts from the Paleocene of western Canada, a record that includes representatives of both families (Huerfanodon, a conoryctid, and Psittacotherium, a stylinodontid). The new records demonstrate not only that taeniodonts occurred at higher latitudes during the early part of the Paleocene in North America, but were exceedingly rare, in keeping with their known occurrences elsewhere. Although taeniodont ecology has been invoked as a possible explanation for their rarity, the comparably sparse records of other large- and small-bodied mammals in local faunas of Paleocene age throughout the Western Interior suggest that taphonomic processes may have played the more significant role.