''Dinohippus'' ( Greek: "Terrible horse") is an extinct

equid 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 ...

which was endemic to

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 the late

Hemphillian The Hemphillian North American Stage on the geologic timescale is a North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 10,300,000 to 4,900,000 years BP. It is usually considered t ...

stage of the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

through the

Zanclean The Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 ± 0.005 Ma (million years ago) and 3.6 ± 0.005 Ma. It is preceded by the Messinian Age of the Miocene Epoch, and f ...

stage of the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58mya) and in existence for approximately . Fossils are widespread throughout North America, being found at more than 30 sites from

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 ...

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

and from

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

all the way down to

Panama Panama, officially the Republic of Panama, is a country in Latin America at the southern end of Central America, bordering South America. It is bordered by Costa Rica to the west, Colombia to the southeast, the Caribbean Sea to the north, and ...

( Alajuela Formation). This most numerous fossils of Dinohippus have been unearthed in the Western United States in

Nevada Nevada ( ; ) is a landlocked state in the Western United States. It borders Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the seventh-most extensive, th ...

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...

, and

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

Quinn originally referred ''"Pliohippus" mexicanus'' to ''Dinohippus'', but unpublished cladistic results in an SVP 2018 conference abstract suggest that ''mexicanus'' is instead more closely related to extant horses than to ''Dinohippus''.

Description

''Dinohippus'' was the most common horse in North America and like '' Equus'', it did not have a dished face (i.e. the head profile did not have a concave section). It has a distinctive passive " stay apparatus" formed from bones and tendons to help it conserve energy while standing for long periods. ''Dinohippus'' was the first horse to show a rudimentary form of this character, providing additional evidence of the close relationship between ''Dinohippus'' and ''Equus''. ''Dinohippus'' was originally thought to be a monodactyl horse, but a 1981 fossil find in Nebraska shows that some were tridactyl. The species ''D. leidyanus'' had an estimated body mass of approximately .

Diet

''D. mexicanus'' fed primarily on C₃ plants in rainforest clearings based on paired carbon and oxygen isotope analysis. Dinohippus leidyanus foot bones

References

{{Taxonbar, from=Q252178 Miocene horses Miocene Perissodactyla Pliocene horses Prehistoric placental genera Messinian life Tortonian life Piacenzian extinctions Miocene mammals of North America Pliocene mammals of North America Blancan Hemphillian Neogene Costa Rica Fossils of Costa Rica Neogene Mexico Fossils of Mexico Neogene Panama Fossils of Panama Neogene United States Fossils of the United States Fossil taxa described in 1955 Equini