The fossil horses from the Farneta Faunal Unit (Early Pleistocene, central Italy): a review with new remarks on the paleobiogeography and biochronology of the Late Villafranchian equids in Western Eurasia

The dispersal of the genus Equus in Western Eurasia at the onset of the Quaternary is an important biochronological event for the evolution of mammal communities. The Farneta Faual Unit (ca. 1.6–1.4 Ma) is one of the latest in the Villafranchian Mammal Age, and its importance is also marked by the first occurrences of the species Praemegaceros obscurus, Pseudodama farnetensis and Bison (Eobison) degiulii. Since it was first described in 1977 by Augusto Azzaroli, the equid material of the Farneta FU has been recognized as belonging to different species by as many authors. In this work, we analyze material referred to the genus Equus from different localities of the Farneta FU (Farneta, Selvella and Pietrafitta). Our analyses identify one middle sized equid, Equusaltidens, and a large sized species, Equus stenonis. Our results have remarkable implications for the Early and early Middle Pleistocene European framework, as they anticipate the first appearance in Western Eurasia of the former species and postpones it for the latter.