Pliocene Bovidae (Mammalia) from the Hadar Formation of Hadar and Ledi-Geraru, Lower Awash, Ethiopia

We revise here the entire collection of Bovidae from the Pliocene Hadar Formation collected at Hadar and Ledi-Geraru, Lower Awash, Ethiopia. Some additions are provided to previously published descriptions, and other forms are described. The complete list includes 28 species, but is dominated by a new species of impala, Aepyceros datoadeni, a kob that we assign to Kobus oricornus, although it belongs to a type distinct from the Omo one, a lineage of alcelaphins that is poorly known elsewhere, Damalborea, and the bovin Ugandax. We also describe a new gazelle, Gazella harmonae, with very peculiar features, including long spiraled horn cores. Changes in the bovid fauna can be detected both within individual lineages, and in the composition of the assemblage. Impala and bovins far outnumber the reduncins in the lower part of the sequence (Basal and Sidi Hakoma members, from ca. 3.8 to 3.2 Ma), but relative abundances become more equal higher up. Biometric changes do occur in the Ugandax and Aepyceros lineages, but are not significant in other lineages. The major evolutionary events occur in the KH1 or KH1/KH2 transition, ca 3.13.0 Ma, with appearance of a third tragelaphin species, of a very small alcelaphin and of a large Aepyceros, and the likely disappearance of K. oricornus.