The Vallesian heteronymous spiral-horned antelope Prostrepsiceros vallesiensis is revised according to some new specimens from the type locality, Ravin de la Pluie, Northern Greece. The new frontlet and isolated horn-core are larger, display weaker horn-core compression, and looser spiralling than in the holotype specimen of P. vallesiensis. These morphological differences are interpreted as representing sexual dimorphism, with the holotype being a female individual of the species. Morphological comparisons and a cladistic analysis of several late Miocene spiral horned antelopes allow for recognizing P. vallesiensis as the most likely ancestor of P. vinayaki, P. libycus and Dytikodorcas, while the P. houtumschindleri lineage probably originated from a pre- P. vallesiensis stock.