Nomenclatures and Taxonomy

Abstract

In this chapter, we compare and redefine each species of horses from South America. We discussed different characters, nomenclature and measurements that used in fossil horses study. We used both morphological and morphometric characters on skulls, mandibles, teeth, and postcranial remains from different localities. Bivariate and multivariate analyses were performed to estimate variation and differences in size and proportions. We think that the cranial and dental morphology and this quantitative multivariate analysis support the recognized in Hippidion genus three valid species. We questioned the use of subgenus Amerhippus. The new molecular data increases the known phenotypic plasticity of horses and consequently casts doubt on the taxonomic validity of the subgenus Amerhippus. In the case of Equus genus, we recognized three valid species (Equus neogeus, Equus andium, and Equus insulatus). We included Equus santaeelenae into the E. insulatus. The status of Equus lasallei needs a revision, but there are small samples to make an evaluation.