Introduction to the fossils of the three-toed horse fauna: The three-toed horse is an extinct genus of the mammal class Perissodactyla, Equidae. It is smaller than modern horses. Both front and rear limbs have three toes, and the middle toe is thick and touching the ground. , the side toes are smaller and not touching the ground. The three-toed horse fauna in the Hezheng area mainly lived in the late Miocene period from 12 million to 5 million years ago.