†Leptotragulinae †Protoceratinae †Synthetoceratinae Protoceratidae is an extinct family of herbivorous North American artiodactyls (even-toed ungulates) that lived during the Eocene through Pliocene.

[2] Protoceratidae was erected by Othniel Charles Marsh in 1891, with the type genus Protoceras and assigned to the Artiodactyla.

Unlike many modern ungulates, they lacked cannon bones in their legs.

These horns were either paired, as in Syndyoceras, or fused at the base, and branching into two near the tip, as in Synthetoceras.

In later forms, the horns were large enough to have been used in sparring between males, much as with the antlers of some modern deer.