Editing Canidae (section)

===Oligocene epoch===
By the [[Oligocene]], all three subfamilies (Hesperocyoninae, Borophaginae, and Caninae) had appeared in the fossil record of North America. The earliest and most primitive branch of the Canidae was Hesperocyoninae, which included the coyote-sized ''[[Mesocyon]]'' of the Oligocene (38–24 Mya). These early canids probably evolved for the fast pursuit of prey in a grassland habitat; they resembled modern [[viverrid]]s in appearance. Hesperocyonines eventually became extinct in the middle Miocene. One of the early Hesperocyonines, the genus ''[[Hesperocyon]]'', gave rise to ''[[Archaeocyon]]'' and ''[[Leptocyon]]''. These branches led to the borophagine and canine [[evolutionary radiation|radiations]].<ref name=Gittleman>Martin, L.D. 1989. Fossil history of the terrestrial carnivora. Pages&nbsp;536–568 in J.L. Gittleman, editor. Carnivore Behavior, Ecology, and Evolution, Vol. 1. Comstock Publishing Associates: Ithaca.</ref>