A model showing the development of the horse's leg over time. The legs from left to right correspond to the Hyracotherium, Mesohippus, Merychippus, Pliohippus, Plesippus and the Equus.
A model showing the development of the horse's teeth over time. The teeth from left to right correspond to the Hyracotherium, Mesohippus, Parahippus, Merychippus, Pliohippus, Plesippus and the Equus.