Pronghorn

Pronghorn in Grand Teton National Park

Wiki Info:
The pronghorn is the fastest land mammal in the Western Hemisphere. Though not an antelope, it is often known colloquially in North America as the prong buck, pronghorn antelope, cabri (native American) or simply antelope because it closely resembles the true antelopes of the Old World and fills a similar ecological niche due to convergent evolution.