Evolution
It is speculated that during the Eocene period, hoofed marsh dwellers carried their body weight mainly on two of the middle toes, which grew to equal size, becoming the Artiodactyla or even-toed hoofed animals. Prior to the close of the Eocene period the side toes of some had dwindled and practically disappeared while the basal pieces or metapodium of the pair of supporting toes became fused together, thus producing the appearance of a cloven hoof.
The mammal with a cloven hoof is an even-toed ungulate of order Artiodactyla as opposed to the odd-toed ungulates of Perissidactyla, like the horse, which have one toe, or the rhinoceros, which has three toes. The five-toed ancestors of the earliest Eocene had already developed feet that suggest odd-toed and even-toed descendants to the modern viewer. Even Phenacodus, the most generalized of the early mammals, has a foot in which the central toe is somewhat larger than the others and could be placed in the division of odd toed ungulates, Perissidactyla.
Read more about this topic: Cloven Hoof
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