Dinocerata

Dinocerata (from the Greek δεινός (deinós), "terrible", and κέρας (kéras), "horn") is an extinct order of plant-eating, rhinoceros-like hoofed mammals famous for their paired horns and tusk-like canine teeth. The earliest dinoceratan, Prodinoceras, appeared in Asia during the Paleocene, but nearly all later types are from North America (dinoceratans must have crossed the Bering land bridge, which may have been exposed during Paleocene-Eocene times). Dinoceratans lived alongside another group of large Eocene plant-eaters, the brontotheres. The most famous dinoceratan is Uintatherium.

Dinocerata
Temporal range: Late Paleocene–Late Eocene
Uintatherium.
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Mammalia
Infraclass:
Eutheria
Superorder:
Laurasiatheria
Order:
†Dinocerata

Marsh, 1872
Families & Genera

See "Taxonomy"

Classification
Eobasileus (left) and Uintatherium (right).

How dinoceratans are related to other mammals is in dispute. They are probably part of the hoofed mammal (ungulate) group and have similarities with some meridiungulates (extinct South American hoofed mammals), namely, the primitive Carodnia of Paleocene South America. Another idea is that dinoceratans are closely related to pantodonts and tillodonts. A more controversial view is that dinoceratans descend from the anagalids, a small group of rabbit-like mammals. They may be related to the ungulatomorph family zhelestidae.

Many dinoceratans are large, but they have one of the smaller brains in relation to body size among the mammals (the smallest brains of the mammal class belong to pantodonts), distinctly smaller than those of later ungulates (hoofed mammals) and other mammals.

Although dinoceratans have traditionally been placed in the superorder Ungulatomorpha, this clade is now considered to be polyphyletic. This is the result of recent genetic and molecular research, which is rewriting the story of mammalian classification. The various members of the Ungulatomorpha are now placed in two very different lineages of placental mammals: Afrotheria (paenungulates) and Laurasiatheria (true ungulates). The dinoceratans are believed to be related to the "true" ungulates (orders Perissodactyla and Artiodactyla plus several extinct groups such as the meridiungulates), and so should be considered members of Laurasiatheria. It is, however, entirely possible that one of the earlier viewpoints may turn out to be correct: that the dinoceratans are related to the pantodonts and tillodonts and should be treated among the Cimolesta, which are thought to be non-placental Eutherians. As it is impossible to extract genetic material from fossils this old, the phylogenetic position of dinoceratans may well shift again in the future.

A 2015 phylogenetic study recovered Dinocerata as closely related to Carodnia, showcasing them as part of the Euungulata assemblage.[1]

Taxonomy and phylogeny

Most experts place the known genera of Dinocerata within one family, Uintatheriidae, and split it into two subfamilies, Uintatheriinae and Gobiatheriinae. Some experts prefer to split Uintatheriidae into three families, with Gobiatherium placed in the monogeneric family Gobiatheriidae, the other Eocene genera in Uintatheriidae proper, and the Paleocene genera Prodinoceras and Probathyopsis placed in the family "Prodinoceratidae".

References
  1. Burger, Benjamin J. (2015). "The systematic position of the saber-toothed and horned giants of the Eocene: the Uintatheres (Order Dinocerata)" (PDF). Utah State University Uintah Basin Campus, Vernal, UT, 84078, United States Of America.CS1 maint: location (link)
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