Megacerops

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Megacerops
Temporal range: Late Eocene
M. coloradensis, Natural History Museum of Los Angeles County
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Mammalia
Order:Perissodactyla
Family:Brontotheriidae
Genus:Megacerops
Leidy, 1870
Species
Synonyms
  • Titanotherium ramosum
  • Menodus peltoceras
  • Brontotherium
  • Brontops
  • Ateleodon
  • Oreinotherium
 
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Megacerops
Temporal range: Late Eocene
M. coloradensis, Natural History Museum of Los Angeles County
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Mammalia
Order:Perissodactyla
Family:Brontotheriidae
Genus:Megacerops
Leidy, 1870
Species
Synonyms
  • Titanotherium ramosum
  • Menodus peltoceras
  • Brontotherium
  • Brontops
  • Ateleodon
  • Oreinotherium

Megacerops ('large horn face') is an extinct genus of the prehistoric odd-toed ungulate family Brontotheriidae, an extinct group of rhinoceros-like browsers related to horses. It was endemic to North America during the Late Eocene epoch (38–33.9 mya), existing for approximately 4.1 million years.[1]

Contents

Description

Restoration of a M. coloradensis pair

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.

A single specimen was examined by M. Mendoza for body mass and was estimated to have a weight of 1,000 kg (2,200 lb).[2] However, M. curtus reached an estimated weight of 3.37 tons, larger than a modern white rhino.[3]

Despite resembling a rhinoceros, it was larger than any living rhinoceros: the living animal easily approached the size of the African Forest Elephant, the 3rd largest land animal today. It stood about 2.5 m (8.2 ft)[4] tall at the shoulders and the body, including the head, could measure 5 m (16 ft) in length.[5] The massive body may have weighed around 2,125–5,000 kg (4,680–11,000 lb).[6][7] It resembled a large rhinoceros, possessing a Y-shaped horn-like protrusion on its nose, with blunt ends.

The dorsal vertebrae above the shoulders had extra long spines to support the huge neck muscles needed to carry the heavy skull. Possibly, it had fleshy lips and a long tongue, perfect for carefully selecting food. The shape of its teeth suggests that it preferred food such as soft stems and leaves, rather than tough vegetation.

Paleobiology

Skeletons mounted as if fighting

The skeleton of an adult male was found with partially healed rib fractures, which supports the theory that males used their 'horns' to fight each other. No creature living in Brontops's time and area except another Brontops could have inflicted such an injury.[8] 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 creodonts or nimravids.

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.

Many remains have been found in South Dakota and Nebraska. In the past, specimens exposed by severe rainstorms were found by Native Americans of the Sioux tribe. The Sioux believed these creatures produced thunderstorms when running over the clouds, and called them 'thunder horses'. Many of the skeletons found by the Sioux belonged to herds which were killed by volcanic eruptions of the Rocky Mountains, which were volcanically active at the time.

Taxonomy

Skeleton formerly referred to Brontotherium hatcheri

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).[9][10]

According to Mihlbachler and others,[11][12] Megacerops includes the species of the genera Menodus, Brontotherium, Brontops, Menops, Ateleodon, and Oreinotherium.

References

  1. ^ PaleoBiology Database: Megacerops, basic info
  2. ^ M. Mendoza, C. M. Janis, and P. Palmqvist. 2006. Estimating the body mass of extinct ungulates: a study on the use of multiple regression. Journal of Zoology
  3. ^ http://museumu03.museumwww.naturkundemuseum-berlin.de/cgi-bin/bridge.pl?a=basicTaxonInfo&taxon_no=47982
  4. ^ [1]
  5. ^ [2]
  6. ^ [3]
  7. ^ [4]
  8. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. pp. 258–259. ISBN 1-84028-152-9. 
  9. ^ J. Clark and J. R. Beerbower. 1967. Geology, paleoecology, and paleoclimatology of the Chadron Formation. Fieldiana
  10. ^ R. L. Carroll. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Company, New York 1-698.
  11. ^ Mihlbachler, M.C. , Lucas, S.G., and Emry, R.J. (2004). "The holotype specimen of Menodus giganteus, and the "insoluble" problem of Chadronian brontothere taxonomy". Paleogene Mammals. Bulletin of the New Mexico Museum of Natural History 26: pp. 129–136. 
  12. ^ Mihlbachler, M.C. (2004). "Phylogenetic Systematics of the Brontotheriidae (Mammalia, Perissodactyla)". PhD dissertation (Columbia University): pp. 757.