The provided diagrams illustrate horse development over a period of 40 million years.
Overall, the horse experienced significant changes including its bone structure and size.
40 million years ago, the ancestors of the horse was little sizes and had a long tail which changed over time. Around 30 million years ago, Eohippus was replaced by Mesohippus which was slightly larger and had stronger bones. Additionally, skin colour of Mesohippus was brighter than that of Eohippus.
The closest ancestors of the modern horse was Merychippus which lived 15 million years ago. They had white shade on their skin. In addition, the leg bones consisted of three separate parts. As far as the modern horses are concerned, they are much larger in size and have a long neck, while their ancestors did not have these features. In addition, the structure of the horse’s leg became stronger as the bones gradually combined over time.In addition, the number of toes gradually decreased from four to three, eventually forming a single hoof in modern horses.
