The Moeritherium species were pig-like animals that lived about 37-35 million years ago, and resembled modern tapirs or pygmy hippopotamuses (they are not believed to be related to either of those animals, however). They were smaller than modern elephants, standing only 70 centimetres (2.3 ft) high at the shoulder and were about 3 metres (9.8 ft) long. They are believed[by whom?] to have wallowed in swamps and rivers, filling the ecological niche now filled by the hippopotamus. The shape of their teeth suggests that they ate soft water vegetation.
The shape of the skull suggests that Moeritherium did not have an elephant-like trunk, but it may have had a broad flexible upper lip like a tapir's for grasping aquatic vegetation. The second incisor teeth formed small tusks, although these would have looked more like the teeth of a hippo than a modern elephant.
In 1901, Charles William Andrews described Moeritherium lyonsi from fossil remains found in the Qasr-el-Sagha formation in the Al Fayyum in Egypt. Andrews described Moeritherium gracile from fossil remains of a smaller specimen found in the same area in 1902 in a fluvio-marine formation, that is a river estuary wetlands to brackish lagoon paleoenvironment. In 1904, the first Moeritherium trigodon fossils were discovered by Charles Andrews in the deposits of an oasis in Al Fayyum. It is also found in other sites around North and West Africa. In 1911, Max Schlosser of Munich divided Moeritherium lyonsi into two species: Moeritherium lyonsi, a large form from the Qasr-el-Sagha formation, and a new large species M. andrewsi from a fluvio-marine formation. In 2006, Moeritherium chehbeurameuri has been described from fossil remains found in the early late Eocene locality of Bir El Ater, Algeria.