the fossils described by Owen were pointed out in a 1932 paper by Sir Clive Forster Cooper. The only species, E. angustidens, was moved to the genus Hyracotherium, which had priority as the name for the genus, with Eohippus becoming a junior synonym of that genus. Many other North American equids were subsequently classified as species of Hyracotherium as well, but this synonymy has recently been questioned. Taxonomy and evolution The type species, H. leporinum, is now regarded as a paleothere, rather than a horse proper. Most other species of Hyracotherium are still regarded as equids, but they have been placed in several other genera, such as Arenahippus, Minippus, Sifrhippus, Xenicohippus, Pliolophus, Protorohippus and the resurrected Eohippus. At one time, Xenicohippus was regarded as an early brontothere. The main stream of horse evolution occurred on the North American continent. See also Equus Evolution of the horse Merychippus Mesohippus References Eocene odd-toed ungulates Eocene mammals of Europe Ypresian genus first appearances Lutetian extinctions Fossil taxa described in 1841