(Argentina) size: 2 ft 4 in/70 cm long The smallest of the known litopterns, Thoatherium probably resembled a small gazelle. The feet and legs were very long for the size of the body, and it must have been a graceful runner.
Although the paired bones of the lower limbs were reduced, they did not fuse. But the reduction of lateral toes which can be seen in both the true horses and in Diadiaphorus is here taken to an extreme. Indeed, the vestiges of its other 2 toes were even smaller than those of the single-toed horse of today. The teeth, too, remained primitive, so it can be assumed that Thoatherium ate foliage rather than grasses.
Having achieved their greatest diversity in the early Miocene, the proterotheres became extinct in the Late Pliocene, about 3 million years ago.
Was this article helpful?