Mesohippus is the smallest skeleton: skull has a low sloped forehead, legs have three toes. Merychippus is the next largest skeleton, lower jaw of the skull is larger and forehead is higher, the leg has three toes with the toes on the side higher than the center toe. Pliohippus skeleton is larger, legs and neck are longer, the jaw on the skull is much larger and the forehead has the greatest slope of the four skeletons shown, the legs have only a center toe that resembles a hoof. Equus is the largest skeleton with the longest legs, no toes and a hoof. Paleontologists have discovered several ancestors of the modern horse.

Based on the skeleton, the skull, and the leg bones, which fossil is the oldest?

Which fossil is most like a modern horse?