Hypsamasia and Palaeoamasia

Comparison of the arsinoitheres Hypsamasia seri (top) and Palaeoamasia kansui from the early Middle Eocene of Turkey.

P. kansui predates H. seri, and had no horns. H. seri is somewhat closer to the late Eocene Crivadiatherium, and may have had incipient horns.

From what is known, both may have been similar in size to pigs or tapirs. Because their fossils have been found in lignified strata, they are assumed to have lived in swampy environments very similar to the ones preferred by Arsinoitherium.

Some experts separate Palaeoamasia, Hypsamasia and Crivadiatherium from Arsinoitherium and place the former three in a different subfamily, "Palaeoamasinae," sometimes elevated as a separate family, "Palaeoamasidae."