''Miohippus'' (meaning "small horse") is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of horse existing longer than most

Equidae Equidae (commonly known as the horse family) is the Taxonomy (biology), taxonomic Family (biology), family of Wild horse, horses and related animals, including Asinus, asses, zebra, zebras, and many extinct species known only from fossils. The fa ...

. It lived in what is now

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

from 32 to 25 million years ago, during the late

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 ...

to late Oligocene. According to the Florida Museum of Natural History, Othniel Charles Marsh first believed ''Miohippus'' lived during the Miocene and thus named the genus using this incorrect conclusion. More recent research provides evidence that ''Miohippus'' actually lived during the

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

period. ''Miohippus'' species are commonly referred to as the three-toed horses. Their range was from Alberta, Canada to

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

Taxonomy

The type species of ''Miohippus'', ''M. annectens'', was named by

Marsh In ecology, a marsh is a wetland that is dominated by herbaceous plants rather than by woody plants.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p More in genera ...

in 1874. It is classified as a member of the subfamily Anchitheriinae following MacFadden (1998).B. J. MacFadden. 1998. Equidae. In C. M. Janis, K. M. Scott, and L. L. Jacobs (eds.), Evolution of Tertiary Mammals of North America 1:537-559.Paleobiology Database ''Miohippus'' entry
Accessed 8 December 2011

Species list

* ''M. anceps'' Marsh, 1874 * ''M. annectens'' Marsh, 1874

Type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

* ''M. assiniboiensis'' Lambe, 1905 * ''M. condoni'' Leidy, 1870 * ''M. equiceps'' Cope, 1879 * ''M. equinanus'' Osborn, 1918 * ''M. gemmarosae'' Osborn, 1918 * ''M. gidleyi'' Osborn, 1904 * ''M. intermedius'' Osborn & Wortman, 1895 * ''M. longicristis'' Cope, 1878 * ''M. obliquidens'' Osborn, 1904 * ''M. primus'' Osborn, 1918 * ''M. quartus'' Osborn, 1918

Description

The species ''M. obliquidens'' dating from 34.9 to 30.0 Ma found in

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

North Dakota North Dakota ( ) is a U.S. state in the Upper Midwest, named after the indigenous Dakota people, Dakota and Sioux peoples. It is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north and by the U.S. states of Minneso ...

South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state, state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Dakota people, Dakota Sioux ...

, and

Nebraska Nebraska ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Ka ...

when calculated for estimated body mass were within the margin of 25 to 30 kg (55 to 66 lbs). ''Miohippus'' became much larger than ''Mesohippus''. They weighed around 40 to 55 kilograms. They were somewhat larger than most earlier

horse ancestors, but still much smaller than modern horses, which typically weigh about 500 kilograms. ''Miohippus'' was larger than ''Mesohippus'' and had a slightly longer skull. Its facial fossa was deeper and more expanded, and the ankle joint was subtly different. ''Miohippus'' also had a variable extra crest on its upper molars, which gave it a larger surface area for chewing tougher forage. This would become a typical characteristic of the teeth of later equine species. ''Miohippus'' had two forms, one of which adjusted to the life in

forest A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...

s, while the other remained suited to life on

prairie Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the ...

s. The forest form led to the birth of '' Kalobatippus'' (or ''Miohippus intermedius''), whose second and fourth finger again elongated for travel on the softer primeval forest grounds. The ''Kalobatippus'' managed to relocate to

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via the Bering Strait land bridge, and from there moved into

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

, where its

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s were formerly described under the name ''Anchitherium''. ''Kalobatippus'' is then believed to have evolved into a form known as '' Hypohippus'', which became extinct near the beginning of the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58 As many as eight species of ''Miohippus'' were described from the John Day Formation of Oregon, but recent work on the dental variation has determined that only one species of ''Miohippus'' was present within a given member.

References

External links

* * * {{Taxonbar, from=Q942905 Anchitheriinae Fossils of Canada Paleontology in Alberta Eocene horses Oligocene horses Eocene mammals of North America Oligocene mammals of North America Prehistoric placental genera Eocene genus first appearances Oligocene extinctions Fossil taxa described in 1874 Taxa named by Othniel Charles Marsh

Taxonomy

Species list

Description

See also

References

External links