The International Code of Zoological Nomenclature states that the earliest recorded scientific name for an organism becomes the official name. This seems fair, but the system is flawed. Textbooks show the sequence of fossil ancestors of the modern horse as Pliohippus, Merychippus, Mesohippus, and the first horse ancestor, Hyracotherium. The last of these looks out of place. Hyracotherium was once more sensibly called Eohippus; this descriptive name means 'dawn horse'. The suffix 'hippus' (horse) is consistent with others in the list. Eohippus also sounds pleasant. The name was changed when it was discovered that a fossil fragment that had been named Hyracotherium was really from the same animal that had until then been called Eohippus.