It also acts like a rubber band, and helps the foot straighten out after the zebra takes a step. The first ungulates were called condylarths. These animals lived about 65 million years ago and went extinct about 35 million years ago. There were many types of condylarths. One type was the ancestor of the horse family.
Zebras are in the horse family.
The scientific name of the horse family is Equidae. The first Equidae, or equids, had four toes on each leg. As time passed, the foot changed and only one toe was left. The toe is covered by a hoof. The hoof is a special type of toenail.