The diagram illustrates the evolutionary stages of horses with greater emphasis on their foot structure.
Overall, horses have undergone several significant changes in body size and foot structure. Moreover, their feet evolved from ones with multiple digits into a single hoof, enhancing mobility and stability.
In the earliest stage, the Eohippus, which existed 40 million years ago, was relatively small and had four slender toes. Around 10 million years later, it evolved into the Mesohippus, which was larger in size and had three toes, with the middle ones being dominant as the two side toes diminished.
The Merychippus lived 15 million years ago, going through significant adaptations. Its body became bigger, and its middle feet evolved, which nearly matched the side toes, with the reduction in joints in each toe. The Modern horse displayed a significant increase in size with longer and thicker tail. The feet fused into a single hoof, which greatly enhanced running efficiency.
