Thoatherium is an extinct genus of litoptern mammal. With a length of 70 centimeters (2.3 ft), the gazelle-like Thoatherium was the smallest 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 generalized teeth, Thoatherium fed on soft leaves rather than on tough grasses.