The diagrams below show the development of the horse over a period of 40 million years.

The layout depicts how the horse evolved over a 40 million-year period. Overall, four stages are displayed, commencing with Eohippus and finalizing with the development of the modern horse. 40 million years ago, the primitive horse, Eohippus, was comparatively small with a short tail. Its defining characteristic, however, was the structure of its foot, which consisted of 4 digits. Each of the digits was relatively small. 10 million years later, it had evolved into the larger Mesohippus, with a prolonged tail and a foot structure of triple digits. Following this, in the later stage of development, Merychippus stepped into another evolution 15 million years ago. It was a similar in size to Mesohippus, and was also characterized by 3 digits on its feet, but now the digits on the feet were larger in shape, divided into segments, and the middle digit was very prominent. To wrap up, the modern horse massively evolved. It developed in a way that it is bigger than its predecessors, with a large mane and its foot structure is a single and distinctively large digit.