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Horse What is a Horse? History, Characteristics and Uses History Equus caballus or the horse is a mammal. Horses, donkeys, asses and ponies descended from a small dog like creature called hyracotherium. It is common to think of horse evolution as a straight line traceable back to one species, but that is not the case. Over the eons there were many species and sub-species each developing and evolving in response to their particular habitat. The horse has several clues to its evolution. The chestnut, a growth of horny substance on the bone below the knee and the ergot beneath the fetlock are the remains of toenails.  The splint bones (second and fourth metatarsal in the back and metacarpal in the front) and canon (third metatarsal and metacarpal) bones were toe bones. The horse essentially stands on the tips of its fingers and toes.  Primitive horses were small, standing not much above 14 hands (56 inches/141 cm). Modern horses are divided into three classifications: heavy horses, light horses and ponies. The size of modern horses ranges from 5 hands (20 inch/ 50 cm) to 19 hands (76 inch/192cm).

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