Dinocerata, from

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

(), "terrible", and (), "horn", or Uintatheria, is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

order of large herbivorous hoofed mammals with horns and protuberant canine teeth, known from the

Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...

and

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

of Asia and North America. With body masses ranging up to they represent some of the earliest known large mammals.Spencer G. Lucas, Robert M. Schoch 19. "Dinocerata" in: Evolution of Tertiary Mammals of North America: Volume 1, Terrestrial Carnivores, Ungulates, and Ungulate like Mammals (1998)

Description

Uintatheriids are suggested to have been

browsers Browse, browser, or browsing may refer to: Computing *Browser service, a feature of Microsoft Windows to browse shared network resources *Code browser, a program for navigating source code *File browser or file manager, a program used to manage f ...

. Over the course of their evolution, dinoceratans underwent a great increase in body size, from a weight of in the earliest species to a weight of up to in the largest species, co-inciding with the development of fully graviportal limbs with a

digitigrade In terrestrial vertebrates, digitigrade ( ) locomotion is walking or running on the toes (from the Latin ''digitus'', 'finger', and ''gradior'', 'walk'). A digitigrade animal is one that stands or walks with its toes (phalanges) on the ground, and ...

posture. Later members of the order are noted for their distinctive pairs of horns that develop from the

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

ry and parietal bones of the skull, along with the development of elongated upper canines. The upper incisors were also lost, and the bilophodont nature of the molar teeth was enhanced.

Evolution

The oldest and most primitive members of the group, such as '' Prodinoceras'', appeared virtually simultaneously during the late

in North America and Asia, indicating connection between the two landmasses (probably via

Beringia Beringia is defined today as the land and maritime area bounded on the west by the Lena River in Russia; on the east by the Mackenzie River in Canada; on the north by 70th parallel north, 72° north latitude in the Chukchi Sea; and on the south ...

), with uintatheres continuing to exchange between the landmasses during the Eocene, as suggested by the presence of ''

Uintatherium ''Uintatherium'' ("Beast of the Uinta Mountains") is an extinct genus of herbivorous dinoceratan mammal that lived during the Eocene epoch. Two species are currently recognized: ''U. anceps'' from the United States during the Early to Middle Eoc ...

'' in both North America and China. Uintatheres became extinct towards the end of the Middle Eocene, for unknown reasons.

Classification

The affinities of the group within

Placentalia Placental mammals ( infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distingui ...

have historically been contentious. A 2015 phylogenetic study recovered Dinocerata as part of

Laurasiatheria Laurasiatheria (; "Laurasian beasts") is a superorder of Placentalia, placental mammals that groups together true insectivores (eulipotyphlans), bats (chiropterans), carnivorans, pangolins (Pholidota, pholidotes), even-toed ungulates (Artiodacty ...

, closely related to

ungulate Ungulates ( ) are members of the diverse clade Euungulata ("true ungulates"), which primarily consists of large mammals with Hoof, hooves. Once part of the clade "Ungulata" along with the clade Paenungulata, "Ungulata" has since been determined ...

s and "

condylarth Condylarthra is an informal group – previously considered an Order (biology), order – of extinct placental mammals, known primarily from the Paleocene and Eocene epochs. They are considered early, primitive ungulates and is now largely consid ...

s", with Dinocerata placed as the sister group to the

South American native ungulate South American native ungulates, commonly abbreviated as SANUs, are extinct ungulate-like mammals that were indigenous to South America from the Paleocene (from at least 63 million years ago) until the end of the Late Pleistocene (~12,000 years a ...

group

Xenungulata Xenungulata ("strange ungulates") is an order of extinct and primitive South American hoofed mammals that lived from the Late Paleocene to Early Eocene ( Itaboraian to Casamayoran in the SALMA classification). Fossils of the order are known f ...

. A close relationship with Xenungulata was first proposed in 1985, with the proposed clade containing both groups named Uintatheriamorpha, though other authors have suggested that these similarities are likely to be due to convergence.

Taxonomy and phylogeny

Dinocerata is generally divided into two families, "Prodinoceratidae", containing the most primitive genus '' Prodinoceras,'' with some authors also choosing to include the genus '' Probathyopsis'''','' and Uintatheriidae, containing all other genera. Members of Prodinoceratidae are likely ancestral to Uintatheriidae. The Asian uintatheriid genus '' Gobiatherium'' is often placed into its own separate subfamily Gobiatheriinae, with all other uintatheriids belonging to the subfamily Uintatheriinae. *Order Dinocerata **Family Prodinoceratidae ***'' Prodinoceras'' ***?'' Probathyopsis'' **Family Uintatheriidae ***'' Gobiatherium'' ***'' Probathyopsis'' ***'' Bathyopsis'' ***''

'' ***'' Eobasileus'' ***'' Tetheopsis''

References

{{Authority control * Eocene mammals Eocene extinctions Paleocene first appearances Fossil taxa described in 1872 Mammal orders