"The pronghorn is found nowhere else in the world except the interior western and central north of America. At first sight it certainly does resemble the antelope of the Old World but it is thought to be a classic example of convergent evolution. This is where species develop to inhabit at least two separate places in the world but which share features and behaviors which mean they may resemble each other despite no shared ancestry. To the untrained eye, their appearance would suggest that they are related species even when they are not.
The lone member of its family, the Antilocapridae, the closest relativeof the pronghorn is in fact the giraffids family, which itself now contains only two species, the okapi and giraffe. Yet they do resemble the bovids (to which the antelope belongs) much more than the giraffe. This is because on the plains of North America they filled a niche similar to that of the bovids that evolved in the Old World. They were highly successful too and for a million years there were more than a dozen species in the family. Then we arrived."