User:Abyssal/Prehistory of North America/Selected picture/7

Fossil remains of various horse genera, showing the evolution of their skeletons, skulls and limb bones over time. The uppermost and most recent genus is that of the modern horse, Equus. Below that is Pliohippus, dating back to the late Miocene. Below that and older still is Merychippus of the middle Miocene. The bottom and oldest horse genus is Mesohippus from the late Eocene.
Photo credit: H. Zell