Why is the pronghorn not a true antelope?

The pronghorn is not a true antelope because it belongs to an entirely different biological family, the Antilocapridae, of which it is the sole living member. In contrast, true antelopes belong to the family Bovidae, a diverse group that also includes cattle, sheep, and goats.1234

The most significant physical distinction lies in their horns:

• Pronghorns: Possess unique, branching horns consisting of a hollow sheath over a bony core. They are the only animals that shed their horn sheaths annually.124
• Antelopes: Have unbranched horns that are never shed.1

While both animals are hoofed ruminant mammals within the order Artiodactyla, the pronghorn is native exclusively to North America, whereas true antelopes are Old World animals primarily found in Africa and Asia. The common name "American antelope" is a misnomer that often leads to confusion regarding their true evolutionary relationship.123