Archaeocyon

Archaeocyon ("beginning dog") is the most primitive genus in the subfamily Borophaginae, an extinct subgroup of the family Canidae, which includes living dogs, wolves, and foxes. Fossils of Archaeocyon are known from the Oligocene of the western United States, coming from rocks assigned to the Whitneyan and Arikareean NALMAs (). Species of Archaeocyon are among the earliest known borophagines, although a species of Otarocyon has a slightly earlier first appearance.

Archaeocyon was a comparatively small and unspecialized dog. Its dentition (teeth) suggests a slightly more hypocarnivorous (omnivorous) diet than the otherwise similar Hesperocyon. The skeleton is also generalized, lacking specializations for running and retaining a plantigrade foot posture.

A few derived features of the dentition support a relationship to Borophaginae and Caninae (the subfamily that includes living canids), rather than to the basal canid subfamily Hesperocyoninae. The temporal position of Archaeocyon suggests an affinity to borophagines because the first members of Caninae appear substantially earlier.

Three species of Archaeocyon have been described. The two earlier species, A. pavidus and A. leptodus, differ primarily in size, with A. leptodus being larger. The third species, A. falkenbachi, is the size of A. leptodus and differs from other Archaeocyon species in having a shorter, broader skull.

References:

• Wang, X., R.H. Tedford, and B.E. Taylor. 1999. Phylogenetic systematics of the Borophaginae (Carnivora, Canidae) Bulletin of the American Museum of Natural History, 243:1-391.