Dinohippus is an extinct herbivorous mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

 belonging to the tribe Equini

Equini

Equini is a tribe of herbivorous mammals of the subfamily Equinae, family Equidae, which lived worldwide from the Hemingfordian stage of the Early Miocene to present and in existence for approximately .-Taxonomy:...

, subfamily Equinae

Equinae

Equinae is a subfamily of the family Equidae, which lived worldwide from the Hemingfordian stage of the Early Miocene to present and in existence for approximately .-Taxonomy:...

, which was endemic to North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 from the late Hemphillian

Hemphillian

The Hemphillian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 10,300,000 to 4,900,000 years BP, a period of . It is usually considered to overlap the Tortonian epoch of the Late...

 stage of the Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 through the Zanclean

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 and 3.6 Ma ± 0.005 Ma . It is preceded by the Messinian age of the Miocene epoch, and followed by the Piacenzian age....

 stage of the Pliocene

Pliocene

The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

 (10.3—3.6 mya) and in existence for approximately .

Taxonomy

Dinohippus was named by Quinn in 1955 and assigned to Equidae by Quinn that same year, by B. J. MacFadden (1986) and R. L. Carroll (1988); and to Equini by MacFadden.

It was the most common horse in North America and like Equus

Equus (genus)

Equus is a genus of animals in the family Equidae that includes horses, donkeys, and zebras. Within Equidae, Equus is the only extant genus. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. This article deals primarily with the extant species.The term equine...

, Dinohippus did not have a dished face. It has a distinctive passive "stay apparatus," formed by bones and tendons, to help it conserve energy while standing for long periods. Dinohippus is 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.

Morphology

Three specimens were examined for body mass by M. Mendoza, C. M. Janis, and P. Palmqvist as well as M. T. Alberdi, J. L. Prado, and E. Ortiz-Jaureguizar.

• Specimen 1: 567.7 kg (1251 lbs)
• Specimen 2: 536.5 kg (1182.7 lbs)
• Specimen 3: 224.0 kg (493.8 lbs)

Fossil distribution

Fossil distribution is widespread throughout North America with more than 30 sites from Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

 to Alberta, Canada to Central Mexico.

Dinohippus interpolatus

Dinohippus interpolatus (synonomized with Pliohippus bakeri), D. leardi, D. leidyanus (syn. Pliohippus edensis, Pliohippus osborni)

• Taxonomy: Hippidium interpolatum was named by Cope (1893) and said originally to have been placed in. Its type locality is Goodnight Bed Formation. Hippidium interpolatum was a grazing and browsing animal.
• Morphology: One specimen was examined by M. Mendoza, C. M. Janis, and P. Palmqvist. The body mass was estimated to be 119.7 kg (263.8 lbs).

Mendoza et al. (2006:99) state that D. leidyanus body mass ~200 kg.

Dinohippus mexicanus

Dinohippus mexicanus (synonomized with Equus mesamexicanus, Hippotigris ocotensis, Protohippus muelleri),

• Taxonomy: was named by Lance in 1950 and recombined as Asinus mexicanus by Quinn (1955); it was recombined as Dinohippus mexicanus by May and Repenning (1982), MacFadden (1984), MacFadden (1986) and Kelly (1998).
• Morphology: One specimen was examined by M. Mendoza, C. M. Janis, and P. Palmqvist. The body mass was estimated to be 259.7 kg (572.5 lbs).

Dinohippus spectans

Dinohippus spectans (synonomized with Equus mesamexicanus, Hippotigris ocotensis, Protohippus muelleri),

• Taxonomy: was named by Cope in 1880, Zittel (1893), Roger (1896), Matthew (1899), Trouessart (1905), Merriam and Sinclair (1907), Cope and Matthew (1915), Osborn (1918), Merriam and et al. (1925), Hay (1930), Stirton (1940), Quinn (1955), Macdonald (1959) and Shotwell (1963). It was recombined as Hippidion spectans by Trouessart (1892), Trouessart (1898) and Hay (1902); it was recombined as Protohippus spectans by Matthew (1909); it was considered a nomen dubium by Macdonald (1992). It was again recombined as Dinohippus spectans by Creely and et al. (1982), Kelly and Lander (1988), Hulbert (1989), Kelly (1995) and Kelly (1998).

Sister taxa

Astrohippus

Astrohippus

Astrohippus is an extinct member of the Equidae tribe Equini, the same tribe that contains the only living equid genus, Equus. Fossil remains have been found in the central United States, Florida, and the Mexican states of Chihuahua, Jalisco, and Guanajuato...

, Calippus

Calippus

Calippus may refer to:* Calippus of Syracuse, a student of Plato and Syracusean tyrant.* Callippus, a Greek astronomer and mathematician.* Calippus , a small lunar crater.* Calippus, an extinct relation of the modern horse....

, Equus

Equus (genus)

Equus is a genus of animals in the family Equidae that includes horses, donkeys, and zebras. Within Equidae, Equus is the only extant genus. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. This article deals primarily with the extant species.The term equine...

(synonomized with Allozebra, Asinus, Onager, Plesippus, Neohippus, Equus semiplicatus, Equus tau), Hippidion

Hippidion

Hippidion was a Welsh pony-sized horse that lived in South America during the Pleistocene epoch, between two million and 10,000 years ago....

, Onohippidium, Pliohippus

Pliohippus

Pliohippus is an extinct genus of Equidae, the "horse family". Pliohippus arose in the middle Miocene, around 12 million years ago, probably from Calippus. It was similar in appearance to Equus, but had two long extra toes on both sides of the hoof, externally barely visible as callused stubs...

, Protohippus

Protohippus

Protohippus is an extinct genus of horse....

(syn. Eoequus)