Moropus belonged to the schizotheriine subfamily of chalicotheres, and has the best fossil record of any member of this group; numbers of individuals, including complete skeletons, have been found.

Though not as adept at bipedalism as the related Chalicotherium, it may nonetheless have reared up on two legs to browse on vegetation, using its claws to hook into the bark of a tree or using them to pull down leaves that would otherwise have been unreachable.

[3] After its discovery, multiple more complete specimens were discovered in the Miocene strata of the John Day Fossil Beds of Oregon.

At first, Marsh believed that Moropus belonged to the order Edentata, which historically included any mammal that lacked incisor teeth.

[6] In 1913, Olof August Peterson named a new species of Moropus, M. hollandi, from limb elements recovered in 1901, at first mistakenly assigned to M.

[13] Chalicotheres are part of the order Perissodactyla, which includes modern equines, rhinoceroses, and tapirs, as well as extinct groups like brontotheres.

[16][17] A 2004 cladistic study alternatively recovered Ancylopoda as sister to all modern perissodactyls (which includes Equoidea and Ceratomorpha), with the brontotheres basal to both.

[18] In their 1914 monograph on chalicotheres, Holland and Peterson listed three subfamilies: Moropodinae (Ancylotherium, Moropus, and Nestoritherium), Macrotheriinae (including Chalicotherium, Circotherium, and Macrotherium) and Schizotheriinae (Pernatherium and Schizotherium).

Palaeontologist Arthur Smith Woodward, in 1925, concurred with the system used by Holland and Peterson, and only altered the placements of a few genera.

[23] Some species of Moropus, such as M. elatus, were among the largest chalicotheres,[5] standing about 2.4 m (8 ft) tall at the shoulder and with a body weight around the size of a large rhinoceros.

[4] The lower incisors, of which there were three on each side,[4] are procumbent (protruding), spatulate, and were separated from the cheek teeth by a long diastema.

Three large, highly compressed claws were present on each of the front feet, supported inside by fissured bony phalanges.

However, while not as extreme as in Chalicotherium, Moropus' pelvis still bore some adaptations for bipedal stance, such as a long ischium, and changes in the structure of the hindfoot (i.e. the shortening and widening of the astragalus) to increase its weight-bearing capabilities without sacrificing limb length.

[27] It was suggested by William Diller Matthew that Moropus used its claws to dig for buried plant matter and water sources,[20] though as it did not live in an arid environment, this is unlikely.

[27] Russian palaeontologist Alexey Borissiak suggested, based on Borissiakia from Kazakhstan, that schizotheriines may have fed bipedally, wedging their front claws into tree bark for support.

[30] In 1943, Swiss palaeontologist Samuel Schaub suggested that the related Ancylotherium used its forelimbs to pull down vegetation,[31] much as in chalicotheriines.

The matter was discussed by Olof August Peterson and William Jacob Holland in their monograph, in reference to two different mature size groups that had been noted.

Based on the relative subtetly of these differences, which did not, to them, indicate sexual dimorphism, the smaller morph was decided to probably be separate, and Moropus petersoni was retained as a taxon.

[4] However, Margery Chalifoux Coombs suggested that there was, in reality, no reason to assume that sexual dimorphism was absent, and opted to sink M. petersoni into M. elatus.