| Here is a skeletal reconstruction of the world-famous Hagerman Horse, Equus simplicidens, whose bones and teeth constitute the most commonly observed vertebrate fossil encountered in the 3.0 million-year-old Coso Formation, Inyo County, California. Image courtesy of Hagerman Valley Hisotrical Society Museum, Idaho. Equus simplicidens is considered the earliest member of the genus Equus, which includes all modern equids such as horses, zebras and donkeys. The Hagerman Horse was roughly the size a living African Grevy's zebra, to which Equus simplicidens is actually more closely related than to what might be thought a more logical choice: the modern domesticated horse. |