First mesonychid from the Clarno Formation (Eocene) of Oregon, USA
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Date
2019-06
Authors
Robson, Selina V.
Famoso, Nicholas
Davis, Edward Byrd
Hopkins, Samantha S.B.
Journal Title
Journal ISSN
Volume Title
Publisher
Palaeontologia Electronica
Abstract
A recently identified left dentary of Harpagolestes cf. uintensis represents the first
mesonychid material known from the Pacific Northwest. The specimen is from the Hancock Quarry (Clarno Unit, John Day Fossil Beds National Monument), which is in the uppermost subunit of the Clarno Formation (middle Eocene, ~40 Ma). The sediments of the Hancock Quarry were deposited by a meandering river system during the middle Eocene when north-central Oregon had a subtropical climate. As with many other mammals from the Hancock Quarry, Harpagolestes participated in an Asian-North American faunal interchange; species of Harpagolestes are known from the Eocene of both continents. Harpagolestes was carnivorous, and members of the genus were likely bone-crushers. Characteristic bone-crushing wear is visible on the occlusal surfaces of the Hancock Quarry specimen’s premolars and molars. With the aid of CT scans, it has been determined that the Hancock Quarry Harpagolestes contains the alveoli for c1, p1-2, and m3, and preserves the crowns of p3-4 and m1-2. The molariform teeth have a large, conical trigonid with a bulbous talonid. The protoconid of p3 and p4 is tilted posteriorly. This specimen of Harpagolestes cf. uintensis represents a new large carnivore in the Hancock Quarry ecosystem, adds to the known diversity of the Oregon middle Eocene, and is the only known occurrence of a mesonychid in the Pacific Northwest.
Description
13 pages
Keywords
Mesonychia, Clarno Formation, Pacific Northwest, Eocene, Mammalia