An early Pliocene hipparionine horse from the Canadian Arctic

Abstract

A partial skull of a juvenile hipparionine equid from Ellesmere Island, Canada, is the northernmost fossil record of a horse (78°33' N). Biostratigraphical analysis of the associated fossil biota suggests an age of 3·5 to 4 Ma (early Pliocene). Preserved facial characteristics of the equid include a very reduced preorbital fossa located posterior to the infraorbital foramen. The deciduous premolars have low crown heights, complex fossette plications, multiple pli caballins, and oval, isolated protocones. The teeth are quite large, corresponding to an adult with a tooth row length of c. 150 mm. This combination of facial and dental characteristics and large size is not observed in any contemporaneous North American hipparionine, but is instead found in some Asiatic hipparionines, most notably Plesiohipparion. If the resemblance is not a result of convergence, then this represents the first record of an Old World hipparionine dispersing to North America. Alternatively, the specimen may represent a hitherto unknown, high-latitude hipparionine clade.