While this originally stemmed from perceived similarities to sirenians (manatees and dugongs), morphological data and isotope analysis has since lent it a great deal of support.

The elongated body of Moeritherium, and the high position of its eyes and ears, are likely a result of its lifestyle, and its unusual dentition is likely an adaptation for feeding on water plants.

The type species of Moeritherium, M. lyonsi, was discovered in strata belonging to the Qasr el Sagha Formation in the Fayum fossil deposits of Egypt.

[2][3] It was described in 1901 by Charles William Andrews, who proposed two hypotheses for its phylogenetic position: either Moeritherium was part of the obsolete order Amblypoda, or it was an early proboscidean, perhaps "a generalised forerunner of the Mastodon type".

[4] The lack of material overlap has made it difficult to determine how M. gracile actually relates to M. lyonsi, as their holotypes consist of different skull elements; the type specimen of the former (CGM C.10003) is a palate with no associated lower teeth.

[3] Two years later, a fourth taxon, M. trigodon, was described, also by Andrews, based on remains recovered from the "fluvio-marine beds"[5][6] (equivalent to the Jebel Qatrani Formation)[7] around the lake Birket-el-Qurun.

In 1971, German zoologist Heinz Tobien opted to synonymise the entire genus with M. lyonsi,[10] though he chose to altogether disregard, Deraniyagala's species, likely as they were poorly diagnostic.

[13] In a 2021 paper describing a new genus (Dagbatitherium tassyi) Lionel Hautier et al. ran a phylogenetic analysis which recovered Moeritherium as sister to a clade including deinotheres and elephantiforms.

At the shoulder, this species measured only 70 cm (2.3 ft), and it had a body mass of 235 kg (518 lb),[15] though Moeritherium exhibited strong sized-based sexual dimorphism, so this estimate should be considered a crude average.

[1] Unlike later proboscideans, the naris (nasal cavity) was fairly close to the front of the skull,[18] which, in conjunction with the length of the mandible, suggests that a conventional trunk was absent in Moeritherium.

[22] The environment of the Jebel Qatrani Formation, from which some specimens of Moeritherium are known, have been described as a subtropical to tropical lowland plain by Bown, who further suggests the presence of streams and ponds.

[23] Based on the occurrence of birds that are associated with water (such as ospreys, early flamingos, jacanas, herons, storks, cormorants and shoebills), Rasmussen and colleagues similarly inferred that the environment featured slow-moving freshwater with a substantial amount of aquatic vegetation.

Although lithology suggests that most fossils were deposited on sandbanks after being transported by currents, the authors argue that swamps could have easily formed along the banks of the river that was present during the Oligocene and may account for the mudstone found in certain quarries.

The absence of other birds typical for such an environment may be explained either through sampling bias or due to the fact that said groups had simply not yet been present in Oligocene Africa.

[25] In a 2001 paper Rasmussen et al. argued that the sandstone and mudstone of the formation likely formed as sediments were aggraded by a system of river channels that emptied towards the west into the Tethys.

[26] Overall this indicates that this region was a part of an extensive belt of tropical forest that stretched across what is now northern Africa, which would gradually give rise to open woodland and even steppe the further one was to travel inland.