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.
Every animal has a genus name and a species name.
The genus and species name of humans is Homo sapiens. The genus name of all horses and zebras is Equus. The species name of the zebra depends on the type of zebra. One type is Equus zebra, another type is Equus burchelli, and a third is Equus grevyi. The extinct quagga was Equus quagga.