Cranium ofEquus insulatus(Mammalia, Equidae) from the middle Pleistocene of Tarija, Bolivia

Abstract
The first reported cranium (and associated mandible) of Equus insulatus is described from the middle Pleistocene (Enseñadan) Tarija Formation of southern Bolivia. This specimen reveals that E. insulatus, previously only known from fragmentary material, is morphologically and phylogenetically intermediate within the genus Equus and closely related to the common South American species E. andium. It also confirms that the subgenus Amerhippus, which includes all South American species within the genus Equus, is a valid, monophyletic taxon.