Early Gaited Horses
Hyracotherium 

     These small ancestors of modern horses were half a metre or less in length -- about the size of a fox terrier. Compared to living horses, their legs were shorter, they had longer heads relative to their bodies, and a more complete series of teeth. They had three toes on their hind feet and four on their forefeet. Each toe had a pad on its underside, like dogs have. Modern horses have long legs, each ending in a single, powerful toe with a hoof -- but no pad. Eohippus lived during the early part of the Tertiary (about 50 million years ago). Although these dawn horses were present in Europe as well as North America, the mainstream of horse evolution occurred on the latter continent. 

  Analysis of fossilized hoof prints makes a convincing case that Eohippus traveled at good clip, utilizing the gait known as the running walk - - the characteristic gait of Tennessee waking horses, Icelandic ponies, and Paso Finos, in which the length of the stride is extended and only one or two feet are in contact with the ground at any given time. This provides evidence that the running walk, though associated with only certain breeds these days, is nonetheless an instinctive and natural gait, rather than (as is sometimes argued) one that is artificial and man-taught" .