Haplohippus is an extinct horse genus that lived during the Miocene epoch. It is believed to have originated in North America and spread to other parts of the world. Synonyms for Haplohippus include Anchitherium, Megahippus, and Merychippus. These synonyms may be used interchangeably depending on the context, and they all refer to a similar type of horse. The discovery of fossils belonging to Haplohippus and its synonyms has contributed significantly to the study of equine evolution, providing insights into the evolution of horses from their early ancestors to the present-day.