Thoatherium

Thoatherium (meaning "active swift-beast") is an extinct genus of litoptern mammals from the Early Miocene of Argentina. Fossils of the genus have been found in the Santa Cruz Formation in Argentina. With a length of , the gazelle-like Thoatherium was a small representative of the order Litopterna. Judging from its long legs, it was a fast runner. Thoatherium had remarkably reduced toes; only one horse-like hoof remained. Thoatherium even lacked splint bones, which are remnants of the second and fourth toe found in modern horses. Judging from its generalised, brachydont teeth, Thoatherium fed on soft leaves rather than on tough grasses.thumb|left|Life reconstruction by Charles R. Knight == Taxonomy == Thoatherium is currently grouped within the family Proterotheriidae, a family of similarly hooved litoptern notoungulates. The closest relative of the genus is Diadiaphorus.

Phylogeny of Proterotheriidae, including Thoatherium, after McGrath et. al (2019) (Polyphyletic taxa in pink).{{clade|{{clade |1= |2={{clade |1= |2={{clade |1=Paramacrauchenia |2={{clade |1=Anisolambda |2= |3={{clade |1=Lambdaconus lacerum |2={{clade |1=Paranisolambda|style1=background-color:pink; |2={{clade |1=Picturotherium |2={{clade |1= |2={{clade |1=Anisolophus floweri |2={{clade |1= |2={{clade |1= |2={{clade |1=Villarroelia |2={{clade |1=Tetramerorhinus fleaglei |2={{clade |1=Tetramerorhinus prosistens |2= }} }} }} }} }} }} }} }} }} }} }} }} }} }}|style=font-size:85%; line-height:85%;|label1=Proterotheriidae}}