Skull of a New Mesonychid (Mammalia, Mesonychia) from the Late Paleocene of China

Abstract

Cranial remains of Mesonychidae are poorly known from the Paleocene of Asia. A wellpreserved late Paleocene mesonychid skull from Anhui Province in China is described here as a new genus and species, Sinonyx jiashanensis. The new species has a primitive dental formula of 3.1.4.3/3.1.4.3 and distinctive cheek teeth; P3 is three-rooted, P4 lacks a metacone, the buccal cingula are distinct on P4–M3, M3 lacks a metastyle, the talonid of p3–4 is trenchant and square-shaped, and m1 and m3 lack a metaconid. Resemblances of the new genus to Ankalagon, together with the common presence of Dissacus on both continents, suggest that North America and Asia shared a common mesonychid fauna during the late Paleocene. Comparison of the new skull to Hapalodectes supports removal of Hapalodectinae from Mesonychidae, and suggests that mesonychids are closer to archaeocetes than either is to hapalodectids.