Protomarctus is an extinct monospecific genus of the Borophaginae subfamily of canids native to North America. They lived during the Middle Miocene 16.0—13.6 Mya, existing for approximately . It was an intermediate-size canid, and more predaceous than earlier borophagines.
The first specimen was found in Thomson Quarry, Sheep Creek Formation, Nebraska in a Hemingfordian layer. Specimens have since been found in present-day Colorado, as far west as California and as far southwest as New Mexico. They were short-faced, heavy-jawed canines.
References
Further reading
Martin, L.D. 1989. Fossil history of the terrestrial Carnivora. Pages 536 - 568 in J.L. Gittleman, editor. Carnivore Behavior, Ecology, and Evolution, Vol. 1. Comstock Publishing Associates: Ithaca.