''Mesohippus'' (

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

: / meaning "middle" and / meaning "horse") is an extinct genus of early horse. It lived 37 to 32 million years ago in the

Early Oligocene The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/ Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chattian ...

. Like many fossil horses, ''Mesohippus'' was common in North America. Its shoulder height is estimated about 60 cm tall.

Description

''Mesohippus'' had longer legs than its predecessor ''

Eohippus ''Eohippus'' is an extinct genus of small equid ungulates. The only species is ''E. angustidens'', which was long considered a species of ''Hyracotherium''. Its remains have been identified in North America and date to the Early Eocene (Ypresian ...

'' and stood about 60 cm (6 hands) tall. This equid is the first fully tridactyl horse in the evolutionary record, with the third digit being longer and larger than its second and fourth digits; ''Mesohippus'' had not developed a hoof at this point, rather it still had pads as seen in ''

Hyracotherium ''Hyracotherium'' ( ; "hyrax-like beast") is an extinct genus of very small (about 60 cm in length) perissodactyl ungulates that was found in the London Clay formation. This small, fox-sized animal was once considered to be the earliest know ...

'' and '' Orohippus''.MacFadden, B. J.. 1992. Fossil Horses: Systematics, Paleobiology, and Evolution of the Family Equidae. Cambridge University Press, Cambridge. The face of ''Mesohippus'' was longer and larger than earlier equids. It had a slight facial fossa, or depression, in the skull. The eyes were rounder, and were set wider apart and farther back than in ''Hyracotherium''. Mesohippus 01

Unlike earlier horses, its teeth were low crowned and contained a single gap behind the front teeth, where the

bit The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...

now rests in the modern horse. In addition, it had another grinding tooth, making a total of six. ''Mesohippus'' was a browser that fed on tender twigs and fruit. The cerebral hemisphere, or cranial cavity, was notably larger than that of its predecessors; its

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a ve ...

was similar to that of modern horses.

Species

References

{{Taxonbar, from=Q132597 Eocene horses Eocene odd-toed ungulates Oligocene horses Rupelian genus extinctions Transitional fossils White River Fauna Prehistoric placental genera Paleogene mammals of North America Fossil taxa described in 1875

Description

Species

See also

References