The pronghorn, Antilocapra americana, the only living member of the family Antilocapridae, in the mammalian order Artiodactyla. It is often called the "pronghorn antelope," but is not a true antelope. The pronghorn has pronged, or branching, hollow horns with a permanent bony core covered with an outer sheath. These are shed annually after the breeding season. It is about five feet (1.5 m) long and may weigh to 135 pounds (60 kg). One of the fastest animals in the hemisphere, it can run up to 45 miles per hour (72 km/h). Pronghorns live on grasslands and deserts from northern Mexico to southwestern Canada.