Diadiaphorus is an extinct genus of litoptern mammal from the Miocene of Argentina (Ituzaingó, Pinturas, Chiquimil and Santa Cruz Formations) and Bolivia (Nazareno Formation), South America.
Diadiaphorus closely resembled a horse, but was only around 1.2m (03.9feet) in body length with a weight 70kg (150lb), similar to a modern sheep.[1]
It had three toes, only one of which touched the ground. This toe had a large hoof; the two outer toes were rudimentary, much like those of early horses such as Merychippus. Unlike horses, however, Diadiaphorus lacked fused limb bones. Its skull was short and had a relatively large brain cavity. Judging from its low molars, Diadiaphorus ate soft vegetation, such as leaves.[2]