''Mesohippus'' (

Greek Greek may refer to: 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 of all kno ...

: / 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 age (geology), ages or the lower of two stage (stratigraphy), stages of the Oligocene epoch (geology), Epoch/series (stratigraphy), Series. It spans the time between . It is preceded b ...

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

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'' (now strictly defined as a member of the Palaeotheriidae rather than the Equidae). Its rem ...

'' and stood about 60 cm (6

hands A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "han ...

) tall. This equid is the first fully tridactyl horse in the evolutionary record, with the third digit being longer and larger than its first and second 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 extinction, extinct genus of small (about 60 cm in length) perissodactyl ungulates that was found in the London Clay formation. This small, fox-sized animal is (for some scientists) considered t ...

'' 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

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 ...

s. It had a slight facial fossa, or depression, in the skull. The eyes were rounder, and were set wider apart and further 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 communication. 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 represented as ...

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 and its

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

was similar to modern horses.

Species

References

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

Description

Species

See also

References