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How does the fossil record show the evolution of horses?
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Animal
The fallow deer (Dama dama) has been introduced in many areas ever since the Neolithic Period.
The evolutionary history of the horse is one of the best-documented lineages in paleontology. The fossil record reveals a transition from small, forest-dwelling browsers to the large, grazing equines of today, primarily occurring in North America.1
Key evolutionary trends observed in the fossil record include:
- Size and Anatomy: Ancestors like Eohippus (the "dawn horse") were diminutive, standing about 17–20 inches high with arched backs and padded, multi-toed feet. Over millions of years, descendants exhibited increased body size, lengthening of the legs, and the fusion of lower leg bones to support swift running.1
- Foot Structure: Evolution led to a reduction in the number of toes. While Eohippus had four toes on the forefeet and three on the hind feet, later ancestors like Mesohippus had three functional toes. Eventually, the line leading to Pliohippus and the modern genus Equus resulted in a single-toed, hoofed foot.1
- Dentition: Early horses were browsers with low-crowned teeth. As grasslands expanded during the Miocene, ancestors like Parahippus and Merychippus developed high-crowned, crested teeth adapted for grinding abrasive grasses.12
This progression was not a single, steady line but involved various branches and extinctions.1