Hyracotherium

Hyracotherium Temporal range: Early Eocene
Conservation status
Fossil
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Perissodactyla
Family:	Palaeotheriidae
Genus:	Hyracotherium

Hyracotherium ("mole beast") is considered to be the earliest known horse. It was dog-sized and four-toed. It was classified in the mammalia kingdom.It lived in the Northern Hemisphere (in Asia, Europe, and North America) during the Eocene, between 60 and 45 million years ago.

The first fossils of this tiny horse were found in England by the famous paleontologist Richard Owen in 1841. He did not have a full specimen and called it "mole beast". When a full specimen was discovered later it was given the more fitting name Eohippus ("dawn horse"). It wasn't realised until later that the two finds were the same species, and the first published name has priority as the official name. It should be noted that some scientists remain unconvinced that hyracotherium had any connection with horses.

Hyracotherium averaged only 2 feet (60 cm) in length and averaged 8 to 9 inches (20 cm) high at the shoulder. It had 4 hoofed toes on the front feet and 3 hoofed toes on each hind foot. The skull was long, having 44 long-crowned teeth. Hyracotherium is believed to have been a grazing herbivore that ate soft leaves and plant shoots.

In elementary level textbooks, hyracotherium is commonly described as being "the size of a small fox terrier." This arcane analogy was so curious that Stephen Jay Gould wrote an essay about it ("The Case of the Creeping Fox Terrier Clone") in which he exposed a situation that involved textbook plagiarism. The Eohippus gradually died off. However, there is no evidence of how and why they became extinct.

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