The illustration gives information about equine species progressed through the period of 40 million years, with particular prominence on its foot structure.

The illustration gives information about equine species progressed through the period of 40 million years, with particular prominence on its foot structure. Overall, the species has more than doubled in size and especially the foot has completely changed its construction from being five toed to having a hoof. It can be seen that the eohippus which the descendant of the hourse lived 40 million years ago. It only had four short leg. The rudimentary Eohippus horse is quite small in size and its tail was hardly observable. Its two descendants, Mesohippus and Mecrychippus, which are separately estimated to exist 30 million and 15 million years ago, started to have elongated tails and elementary form of the mane. However, their bodies increased slightly in height, the overall stature was largely unchanged. Finally, the mordern horse possesses the most obvious tail and mane; it is also the largest animal whose height and length of body are about three halves of its oldest shown ancestor. The foot of Eohippus only had four separated toes with thin phalanges. In Mesohippus and Merychippus, its reduced to three and the middle phalanx is enlarged so their foot’s morphology starts to resemble a hoof. The modern horse’s foot has the fewest bony structures and the hoof has replaced toes.