Antilocapridae

Antilocapridae is a family of ruminant artiodactyls endemic to North America. Only one species survives, the pronghorn, Antilocapra americana, while every other member of the family is extinct. Pronghorns have a four-chambered stomach, cloven hooves, and small forked horns with a true horny sheath that is shed and regrown outside the breeding season, a trait unique among horned mammals; their lateral toes are entirely lost, leaving only the cannon bones. Their closest living relatives are the giraffids, from which their ancestors diverged in the Early Miocene.