''Megacerops'' ("large-horned face", from '' méga-'' "large" + '' kéras'' "horn" + '' ōps'' "face") is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of the prehistoric

odd-toed ungulate Odd-toed ungulates, mammals which constitute the taxonomic order Perissodactyla (, ), are animals—ungulates—who have reduced the weight-bearing toes to three (rhinoceroses and tapirs, with tapirs still using four toes on the front legs) o ...

(hoofed mammal)

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Brontotheriidae Brontotheriidae is a family of extinct mammals belonging to the order Perissodactyla, the order that includes horses, rhinoceroses, and tapirs. Superficially, they looked rather like rhinos, although they were actually more closely related t ...

, an extinct group of

rhinoceros A rhinoceros (; ; ), commonly abbreviated to rhino, is a member of any of the five extant species (or numerous extinct species) of odd-toed ungulates in the family Rhinocerotidae. (It can also refer to a member of any of the extinct specie ...

-like browsers related to

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...

s. It was endemic to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

during the

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

epoch (38–33.9 mya), existing for approximately .

Description

All of the species had a pair of blunt horns on their snout (the size varying between species), with the horns of males being much larger than those of the females. This could indicate that they were social animals which butted heads for breeding privileges. Despite resembling the rhinoceros, it was larger than any living rhinoceros: the living animal easily approached the size of the

African forest elephant The African forest elephant (''Loxodonta cyclotis'') is one of the two living African elephant species. It is native to humid forests in West Africa and the Congo Basin. It is the smallest of the three living elephant species, reaching a shoulde ...

, the third-largest land animal today. It stood about tall at the shoulders with an overall length(including tail) of . Its skull reached in greatest length, with some specimens possessing substantial canines, up to 70 mm long. ''Megacerops'' resembled a large rhinoceros, possessing blunt Y-shaped horn-like protrusions on its nose up to 43 cm in length. Its mass is estimated to be in the range of The dorsal

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...

e above the shoulders had extra long spines to support the huge neck muscles needed to carry the heavy

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

. The shape of its teeth suggests that it preferred food such as soft stems and leaves, rather than tough vegetation. It may have had fleshy lips and a long tongue for carefully selecting food.

Paleobiology

The skeleton of an adult male was found with partially healed

rib In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the ches ...

fractures, which supports the theory that males used their 'horns' to fight each other. No creature living in ''Megacerops'' time and area except another ''Megacerops'' could have inflicted such an injury. The breathing movements prevented the fractures from completely healing. The adults may have also used their horns to defend themselves and their calves from predators, such as hyaenodonts,

entelodonts Entelodontidae, the entelodonts, are an extinct family of pig-like artiodactyls (even-toed ungulates) which inhabited the Northern Hemisphere (Asia, Europe, and North America) from the late Eocene to the Middle Miocene epochs, about 38-19 millio ...

, ''

Bathornis ''Bathornis'' ("tall bird") is an extinct lineage of birds related to modern day seriemas, that lived in North America about 37–20 million years ago. Like the closely related and also extinct phorusrhacids, it was a flightless predator, occupyi ...

'' or

nimravids Nimravidae is an extinct family of carnivorans, sometimes known as false saber-toothed cats, whose fossils are found in North America and Eurasia. Not considered to belong to the true cats (family Felidae), the nimravids are generally considered ...

Discovery

Fossils were uncovered in the northern plains states. Life-sized models of ''Megacerops'' families (a male, female, and juvenile) are displayed at the James E. Martin Paleontological Research Laboratory, South Dakota School of Mines & Technology, and a different set at the

Canadian Museum of Nature The Canadian Museum of Nature (french: Musée canadien de la nature; CMN) is a national natural history museum based in Canada's National Capital Region. The museum's exhibitions and public programs are housed in the Victoria Memorial Museum B ...

. Many remains have been found in

South Dakota South Dakota (; Sioux: , ) is a U.S. state in the North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota and Dakota Sioux Native American tribes, who comprise a large po ...

and

Nebraska Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the sout ...

. In the past, specimens exposed by severe

rain Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...

storms were found by Native Americans of the

Sioux The Sioux or Oceti Sakowin (; Dakota: /otʃʰeːtʰi ʃakoːwĩ/) are groups of Native American tribes and First Nations peoples in North America. The modern Sioux consist of two major divisions based on language divisions: the Dakota and ...

tribes. The Sioux called them "thunder beasts", a name preserved in the ancient Greek translation (bronto-, ''thunder;'' therion, ''beast''). Many of the

skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

s found by the Sioux belonged to

herd A herd is a social group of certain animals of the same species, either wild or domestic. The form of collective animal behavior associated with this is called '' herding''. These animals are known as gregarious animals. The term ''herd'' i ...

s which were killed by

volcanic eruptions Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often ...

of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...

, which were volcanically active at the time. File:Brontotherium hatcheri.jpg, Skeleton of ''Megacerops'' File:Megacerops sp.jpg, Skeleton of ''Megacerops'' in

Field Museum of Natural History The Field Museum of Natural History (FMNH), also known as The Field Museum, is a natural history museum in Chicago, Illinois, and is one of the largest such museums in the world. The museum is popular for the size and quality of its educational ...

File:Megacerops models.jpg, Reconstruction of ''Megacerops'' in

File:Annual report of the Director to the Board of Trustees for the year .. (1931) (17811304663).jpg, Life-size sculpture of Megacerops family

Taxonomy

''Megacerops'' was named by Leidy (1870). Its type species is ''Megacerops coloradensis''. It was synonymized subjectively with ''Menodus'' by Clark and Beerbower (1967). It was assigned to Brontotheriidae by Leidy (1870), Carroll (1988), Mader (1989), and Mader (1998). According to Mihlbachler and others, ''Megacerops'' includes the species of the genera ''Menodus'', ''Brontotherium'', ''Brontops'', ''Menops'', ''Ateleodon'', and ''Oreinotherium''. File:Brontotherium skull IMG 4441.jpg, Skull in Zurich

References

{{Taxonbar, from=Q135590 Brontotheres White River Fauna Eocene mammals of North America Eocene odd-toed ungulates Priabonian genus extinctions Fossil taxa described in 1870 Taxa named by Joseph Leidy

Description

Paleobiology

Discovery

Taxonomy

See also

References