Ungulates are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. Living ungulates are divided into two orders: the odd-toed ungulates (Perissodactyla) including horses, rhinoceroses, and tapirs; and even-toed ungulates (Artiodactyla) such as cattle, pigs, giraffes, camels, sheep, deer, and hippopotamuses. Cetaceans such as whales, dolphins, and porpoises are also classified as even-toed ungulates, although they do not have hooves. Most terrestrial ungulates use the hoofed tips of their toes to support their body weight while standing or moving. Two other orders of ungulates, Notoungulata and Litopterna, both native to South America, became extinct at the end of the Pleistocene, around 12,000 years ago.
The hippopotamus or hippo, further qualified as the common hippopotamus, Nile hippopotamus, or river hippopotamus, is a large semiaquatic mammal native to sub-Saharan Africa. It is one of only two extant species in the family Hippopotamidae, the other being the pygmy hippopotamus. Its name comes from the ancient Greek for "river horse" (ἱπποπόταμος).
The even-toed ungulates are ungulates—hoofed animals—which bear weight equally on two of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, odd-toed ungulates bear weight on an odd number of the five toes. Another difference between the two is that many other even-toed ungulates digest plant cellulose in one or more stomach chambers rather than in their intestine as the odd-toed ungulates do.
Anthracotherium was a genus of extinct artiodactyl ungulate mammals, characterized by having 44 teeth, with five semi-crescentic cusps on the crowns of the upper molars. The genus ranged from the middle Eocene period until the early Miocene, having a distribution throughout Eurasia. Material subjectively assigned to Anthracotherium from Pakistan suggests the last species died out soon after the start of the Miocene.
Elomeryx is an extinct genus of artiodactyl ungulate, and is among the earliest known anthracotheres. The genus was extremely widespread, first being found in Asia in the middle Eocene, in Europe during the latest Eocene, and having spread to North America by the early Oligocene. It is closely related to cows, pigs, deer, cetaceans, and possibly hippopotamuses.
Anthracotheriidae is a paraphyletic family of extinct, hippopotamus-like artiodactyl ungulates related to hippopotamuses and whales. The oldest genus, Elomeryx, first appeared during the middle Eocene in Asia. They thrived in Africa and Eurasia, with a few species ultimately entering North America during the Oligocene. They died out in Europe and Africa during the Miocene, possibly due to a combination of climatic changes and competition with other artiodactyls, including pigs and true hippopotamuses. The youngest genus, Merycopotamus, died out in Asia during the late Pliocene, possibly for the same reasons. The family is named after the first genus discovered, Anthracotherium, which means "coal beast", as the first fossils of it were found in Paleogene-aged coal beds in France. Fossil remains of the anthracothere genus were discovered by the Harvard University and Geological Survey of Pakistan joint research project (Y-GSP) in the well-dated middle and late Miocene deposits of the Pothohar Plateau in northern Pakistan.
Merycopotamus is an extinct genus of Asian anthracothere that appeared during the Middle Miocene, and died out in the Late Pliocene. At the height of the genus' influence, species ranged throughout southern Asia. With the extinction of the last species, M. dissimilis, the lineage of anthracotheres came to an end. Merycopotamus was closely related to the anthracothere genus Libycosaurus, which, unlike the former, never left Africa. In fact, some African fossils originally placed in Merycopotamus, but are now referred to Libycosaurus.
Sinonyx is a genus of extinct, superficially wolf-like mesonychid mammals from the late Paleocene of China. It is within the family Mesonychidae, and cladistic analysis of a skull of Sinonyxjiashanensis identifies its closest relative as Ankalagon. S.jiashanensis was discovered in Anhui province, China, in the Tuijinshan formation.
Anthracothema was a genus of extinct artiodactyl ungulate mammals that lived in Myanmar during the late Eocene.
Anthracokeryx is a genus of extinct artiodactyl ungulate mammal belonging to Anthracotheriidae that lived in Asia during the middle to late Eocene.
Anthracohyus was a genus of extinct artiodactyl ungulate mammal belonging to Anthracotheriidae that lived in Asia during the middle to late Eocene.
The Jebel Qatrani Formation is a geologic formation located in the Faiyum Governorate of central Egypt. It is exposed between the Jebel Qatrani escarpment and the Qasr el Sagha escarpment, north of Birket Qarun lake near Faiyum. The formation conformably overlies the Qasr el Sagha Formation and is topped by the Widan el Faras Basalt. The age of the formation has been subject to debate, but the most recent research indicates that it covers both the latest parts of the Eocene and the Early Oligocene, spanning over the boundry between these two time periods.
Sivapterodon is an extinct genus of hyainailourid hyaenodont mammal of the polyphyletic tribe Hyainailourini within paraphyletic subfamily Hyainailourinae that lived in Pakistan during the middle Miocene.
Microbunodon was a genus of extinct artiodactyl mammals in the family Anthracotheriidae. It lived between the upper Eocene and the lower Pliocene. Its fossil remains have been found in Europe and Asia.
Helohyidae were a group of artiodactyl mammals. They were most prominent in the mid-to-upper Eocene.
Hyainailourinae ("hyena-cats") is an extinct paraphyletic subfamily of hyainailourid hyaenodonts that lived in Africa, Asia, North America and Europe from the middle Eocene to middle Miocene.
The bothriodontines are a paraphyletic assemblage of anthracotheres that originated from Eurasia in the late middle Eocene (Bartonian). The group can be distinguished from other anthracothere lineages by their upper molars with the mesostyle that is occupied by the transverse valley, selenodont cusps, ventrally concave symphysis, elongated muzzles, with presence of a diastema between the canine and first premolar. The size range of the group ranged from small, basal forms to larger and more derived forms. During their evolution, the bothriodontines undergone a trend from evolving from small basal forms such as Qatraniodon into larger taxa such as Libycosaurus and Merycopotamus. Some genera the snouts became even more elongated and teeth specialized in a folivorous diet, while others like Merycopotamus became wide, heavy and shallow muzzles with teeth more adapted for grazing.
The anthracotheriines are an extinct subfamily of anthracotheres that comprised Paleogene to early Neogene North American and Eurasian artiodactyls. The group contained the genera Anthracotherium, Heptacodon, and Paenanthracotherium, as well as possibly Myaingtherium and Siamotherium. They were small to large sized anthracotheres, and when compared to the other two subfamilies, Microbunodontinae and Bothriodontinae, anthracotheriines are found to occupy a primitive, basal position in the family.
Ancodonta is an infraorder of semiaquatic artiodactyl ungulates including modern hippopotamus and all mammals closer to hippos than to cetaceans (whales). Ancodonts first appeared in the Middle Eocene, with some of the earliest representatives found in fossil deposits in Southeast Asia. Throughout their evolutionary history they have occupied different browsing and grazing niches in North America, Eurasia and Africa. The last continent is notable as they were among the first laurasiatherian mammals to have migrated to Africa from Europe, where they competed with the native afrothere herbivores for the same niches. Of the nearly 50 genera that have existed, only two of them are extant – Choeropsis and Hippopotamus. The interrelationships within the ancodonts has been contended. The traditional notion is that there at minimum two families Anthracotheriidae and Hippopotamidae and were merely sister taxa. However many detailed research of the dentition among ancodonts, as well as how some anthracotheres were similar to hippos in appearance, lead the current consensus where Anthracotheriidae is paraphyletic to Hippopotamidae. Among the anthracotheres members of Bothriodontinae are among the closest to the ancestry of hippos, with the Oligocene aged Epirigenys from Lokon, Turkana, Kenya being the sister taxon to hippos. In response of this many similar clade names have been used for this clade.
Heptacodon is an extinct genus of anthracothere endemic to North America during the Paleogene. They were medium to large-sized anthracotheres with a distinct facial features such short heavy rostrums and robust but simple molars. Heptacodon is a member of the anthracothere subfamily Anthracotheriinae, whose distribution as a whole are in North America and Eurasia. However Heptacodon has only been found in North America, with the species H. yeguaensis from Texas representing the oldest known anthracotheres to be found in North America dating to the middle Eocene. Fossils of this genus have been found in the states of North Dakota, Oregon, South Dakota, Texas, and Utah.
