The horse was called a Eohippus when it had multiple toes.
 In the past, this order contained 14 families, but only threeEquidae (the horse and related species), Tapiridae (the tapir), and Rhinocerotidae (the rhinoceroses)have survived to the present day
 Larger horses have larger bones; therefore, not only do the bones take longer to form bone tissue, but the epiphyseal plates are larger and take longer to convert from cartilage to bone

