An early Pliocene hipparionine horse from the Canadian Arctic

A partial skull of a juvenile hipparionine equid from Ellesmere Island, Can ada, is the northernmost fossil record of a horse (78 degrees 33' N). Biost ratigraphical analysis of the associated fossil biota suggests an age of 3. 5 to 4 Ma (early Pliocene). Preserved facial characteristics of the equid i nclude a very reduced preorbital fossa located posterior to the infraorbita l foramen. The deciduous premolars have low crown heights, complex fossette plications, multiple pli caballins, and oval, isolated protocones. The tee th 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 si ze is not observed in any contemporaneous North American hipparionine, but is instead found in some Asiatic hipparionines, most notably Plesiohippario n. 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.