The animal that we know today as the horse appeared first on the North American continent about 55 million years ago with its four-toed ancestor, Eohippus, meaning “dawn horse.” This small animal was about the size of a fox and made its home in swamplands, feeding off plant life.
Eohippus slowly evolved into Mesohippus, the size of an average collie. Mesohippus had three toes and eventually became an inhabitant of the prairie. Its shape changed as its habitat changed: it grew taller, its teeth and middle toe grew longer and eventually became a hoof. The evolution continued until Equus caballus — the horse as we know it today — was formed.