The tribe Hippotragini consists of the so-called “Horse-like” antelopes, a specious group of large grazing antelopes characterized by striking facial coloration, thick tapering necks, erect manes, and highly specialized for arid regions of Africa and the Arabian Peninsula. Hippotragini consists of three genera: Addax+Oryx, and Hippotragus and currently includes eleven species although that number might increase as more molecular studies are undertaken. The taxonomic history of this group is ongoing as phylogenetic and comparative analyses and techniques continue to improve.
Paleontological evidence suggests that Hippotragini evolved in Eurasia during the early Miocene but it was not until the Pliocene that hippotragin diversity exploded in Eurasia as a response to cooling temperatures and the advancement of grasslands. This was due to continued continental uplift which caused a major expansion of C4 plant diversity. The late Pliocene marked a dramatic shift in hippotragin evolution as climate continued to cool and aridity increased, marking a major expansion of desert conditions during which Addax and Oryx first appeared.
Molecular data largely corroborates fossil data with regard to divergence time estimates and historical biogeography. In all analyses, Hippotragus appears sister to an Addax+Oryx clade. However, molecular data disagrees with paleontological evidence by suggesting that Hippotragus began to differentiate into the species we know today during the Mid-Miocene at approximately 8.5 million years.
The IUCN reports that most species are declining; 1 species has become extinct in historic times, 2 more became extinct in the wild, and four are threatened or endangered (IUCN 2014).
Holland, Wesley. "Systematics of the Tribe Hippotragini (Cetartiodactyla: Bovidae)." (Jan 2015).