Miohippus

Miohippus Temporal range: late Eocene to late Oligocene
Miohippus Fossil skull
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Perissodactyla
Family:	Equidae
Subfamily:	†Anchitheriinae
Genus:	Miohippus Marsh, 1874
Species
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Miohippus (meaning "small horse") was a genus of prehistoric horse existing longer than most Equidae. Miohippus lived in what is now North America during the late Eocene to late Oligocene. Miohippus was a horse of the Oligocene. According to the Florida Museum of Natural History, Othniel Charles Marsh first believed Miohippus lived during the Miocene and thus named the genus using this incorrect conclusion. More recent research provides evidence that Miohippus actually lived during the Paleogene.

Miohippus species are commonly referred to as the three-toed horses. Their range was from Alberta, Canada to Florida to California.

Miohippus was named by Marsh in 1874 and its type is Miohippus annectens. It was assigned to Equidae by Marsh in 1874. It was synonymized subjectively with Mesohippus by Matthew in 1899. It was assigned again by Hay (1902), H. F. Osborn in 1918, Hay (1930), Stirton (1940) and Carroll (1988); and to Anchitheriinae by MacFadden in 1998.

Three specimens were examined for estimated body mass by M. Mendoza, C. M. Janis, and P. Palmqvist. These specimens were estimated to weigh:

The species M. obliquidens dating from 34.9 to 30.0 Ma found in Montana, North Dakota, South Dakota, and Nebraska when calculated for estimated body mass were within the margin of 25 to 30 kg.

Miohippus became much larger than Mesohippus. They weighed around 40 to 55 kilograms. They were somewhat larger than most earlier Eocene horse ancestors, but still much smaller than modern horses, which typically weigh about 500 kilograms.

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