Moeritherium

Moeritherium Temporal range: Late Eocene, 37–35 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
M. trigodon skull cast, at the AMNH.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Proboscidea
Family:	†Moeritheriidae C.W. Andrews, 1906
Genus:	†Moeritherium C.W. Andrews, 1901
Type species
Moeritherium lyonsi Andrews, 1901
Species
†M. gracile C.W. Andrews, 1902 †M. trigodon C.W. Andrews, 1904 †M. andrewsi Schlosser, 1911 †M. chehbeurameuri Delmer et al., 2006

Moeritherium ("the beast from Lake Moeris") is an extinct genus of basal proboscideans from the Eocene of North and West Africa. It was related to elephants and, more distantly, to sea cows and hyraxes.

Moeritherium was a rotund semi-aquatic mammal with short, stubby legs that lived about 37–35 million years ago.^[1] Its body shape and lifestyle demonstrate convergent evolution with pigs, tapirs, and the pygmy hippopotamus. Moeritherium was smaller than most or all later proboscideans, standing only 70 centimetres (2.3 ft) high at the shoulder and weighing 235 kilograms (518 lb).^[2]

The shape of the skull suggests that, while Moeritherium did not have an elephant-like trunk, 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.^[3][4]

Isotopic analysis suggests that Moertherium was amphibious/semiaquatic and probably consumed freshwater plants.^[5]

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,^[6][7] 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.^[1][8] It is also found in other sites around North and West Africa.^[9]

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.^[6][7][10] In 2006, Moeritherium chehbeurameuri has been described from fossil remains found in the early late Eocene locality of Bir El Ater, Algeria.^[11]

Partial M. andrewsi skull with reconstruction at the AMNH

Partial M. andrewsi skull with reconstruction at the AMNH

M. sp. skeleton in Japan

M. lyonsi skull front view, at the Royal BC Museum

1920 illustration.

2016 reconstruction

Moeritherium is not thought to be directly ancestral to modern elephants; it was a branch of Proboscidea that died out, leaving no descendants. There were several species of other basal proboscideans in existence during the Eocene, and some, such as Phiomia and Palaeomastodon, looked comparatively more like modern elephants. However, Moeritherium was clearly a side branch of the proboscidean family tree, having evolved to resemble other rotund semiaquatic mammals such as pigs, tapirs, and hippos instead of having the typical proboscidean body form.^[12]