Dinohippus

Dinohippus Temporal range: Late Miocene–Late Pliocene PreЄ Є O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Perissodactyla
Family:	Equidae
Subfamily:	Equinae
Tribe:	Equini
Genus:	†Dinohippus Quinn, 1955
Species
Dinohippus interpolatus Dinohippus mexicanus Dinohippus spectans

Dinohippus (Greek: Terrible horse), is an extinct herbivorous mammal belonging to the tribe Equini, subfamily Equinae, which was endemic to North America from the late Hemphillian stage of the Miocene through the Zanclean stage of the Pliocene (10.3—3.6 mya) and in existence for approximately 6.7 million years.^[1][2]

Taxonomy

Dinohippus was named by Quinn in 1955 and assigned to Equidae by Quinn that same year, by B. J. MacFadden (1986)^[3] and R. L. Carroll (1988)^[4]; and to Equini by MacFadden.

It was the most common horse in North America and like Equus, 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.^[5] Dinohippus was originally thought to be a monodactyl horse, but a 1981 fossil find in Nebraska shows that some were tridactyl.^[6]

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.^[7][8]

• 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 to Alberta, Canada to Central Mexico.

Species

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).^[9]

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).^[10][11]
• 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).^[12]

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).^[13][14]

Sister taxa

Astrohippus, Calippus, Equus (synonomized with Allozebra, Asinus, Onager, Plesippus, Neohippus, Equus semiplicatus, Equus tau), Hippidion, Onohippidium, Pliohippus, Protohippus (syn. Eoequus)

References

1. ^ Paleobiology Database: Dinohippus basic info.
2. ^ Bruce J. MacFadden: Cenozoic Mammalian Herbivores from the Americas: Reconstructing Ancient Diets and Terrestrial Communities. Annual Review of Ecology and Systematics, Vol. 31, (2000), pp. 33-59
3. ^ B. J. MacFadden. 1986. Late Hemphillian monodactyl horses (Mammalia, Equidae) from the Bone Valley Formation of Central Florida. Journal of Paleontology
4. ^ R. L. Carroll. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Company, New York 1-698
5. ^ Florida Museum of Natural History
6. ^ Horse Ecology
7. ^ 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
8. ^ M. T. Alberdi, J. L. Prado, and E. Ortiz-Jaureguizar. 1995. Patterns of body size changes in fossil and living Equini (Perissodactyla). Biological Journal of the Linnean Society
9. ^ 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
10. ^ S. R. May and C. A. Repenning. 1982. Journal of Vertebrate Paleontology
11. ^ B. J. MacFadden. 1984. Journal of Vertebrate Paleontology
12. ^ 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
13. ^ J. C. Merriam and W. J. Sinclair. 1907. University of California Publications, Bulletin of the Department of Geology
14. ^ R. A. Stirton. 1940. University of California Publications in Geological Sciences