Dawn of the Horses

©Charles R. Knight

Possibly the most synonymized taxon in the entirety of paleontology, Hyracotherium angustidens was named by E. D. Cope in 1875. In 1876 O. C. Marsh described a similar taxon, naming it Eohippus validus. When Clive Forster noted similarities between the genera in 1932 he reassigned E. validus to the senior genus Hyracotherium. When Hyracotherium was redescribed as a paraphyletic taxon in recent years it was noted that H. angustidens and H. validus were identical species, and Marsh's specific name was considered junior to Cope's, but was considered the only valid genus of the two. Therefore, after all of these taxonomic twists, the animal considered the earliest and smallest of the equid lineage was officially renamed Eohippus angustidens. The official list of synonyms for Eohippus stands at 13 junior names, 3 of which are actually subspecies of other synonyms. Regardless, the small horses are interesting in many ways and, more importantly, are animals that have not been discussed here in full, and are therefore deserving of some time in the spotlight.