Thursday, June 9, 2011


Merychippus illustration with leg detail
Horse evolution is a pretty fascinating thing, especially because it is so well documented in the fossil record. The earliest horses date back to Hyracotherium nearly 55 million year ago, and in the millions of years since that tiny toed creature appeared, horses have transitioned and evolved to become the creatures we know today.

Today's animal, Merychippus, lays somewhere near the end of the horse's story. Living between 20-10 million years ago, it is considered one one of the first "True Equines." This particular genus included horses that looked very much like our modern ones. They had only one hoof that touched the ground, as the modern horse does, but they still possessed two vestigial side toes positioned higher up on the leg. Nonetheless, they ran in a way similar to what we know now.

Aside from looking like a strange-legged modern horse, Merychippus is also notable because it is the first horse to have grazing teeth. The teeth of Merychippus suggest that it ate grass rather than browse on branches as earlier horses did. It's name actually means "ruminant horse," because its teeth resemble those of ruminant ungulate. Merychippus, however, did not have a ruminant digestive system, nor do any other horses.

It is believed that Merychippus is the direct ancestor to the other late Miocene horses, including  members of the Hipparion genus which lived until around 700,000 years ago.

Status :  Extinct for approximately 10 million years
Location : North America
Size : Height 35in (89cm)
Classification : Phylum : Chordata -- Class : Mammalia -- Order : Perissodactyla
Family : Equidae -- Genus : Merychippus


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