A cranium of “Gazella” nihensis from Pliocene of Qinghai-Tibetan Plateau and the differentiation of early Antilopina

Fossils of Antilopina were often referred to and classified under the genus name “Gazella”, except for some Miocene spiral horned antelopes; however, their true taxonomic attribution is difficult to determine due to the significant morphological variation observed in large fossil samples. Species of two extant genera within Antilopina that are widely distributed in China are Gazella subgutturosa and Procapra spp. Assigning abundant fossil specimens identified as “Gazella” from China to these two extant groups is particularly challenging. Molecular phylogenetic studies have revealed that Gazella and Procapra belong to two distinct clades within Antilopina. Therefore, the study of fossil “Gazella” is crucial for understanding the differentiation and evolutionary history of Antilopina, which includes a diverse array of genera that lived in Eurasia and Africa. In this article, we describe a newly discovered cranium of “Gazella” nihensis from the Pliocene Epoch on the Qinghai-Tibetan Plateau. The new cranium exhibits several distinctive features: the braincase is considerably elongated, with the occipital condyles protruding caudally beyond the paroccipital process; the cranial-facial axis is weakly curved, and the horn cores are strongly inclined caudally. The morphology is distinct from most other members of Antilopina. We testified the view that “Gazella” nihensis is possibly related with the living Procapra because of these specialized features. Interestingly, in “Gazella” nihensis, the elongated braincase that is less bent from the facial axis resembles that of the living Litocranius walleri; and the strongly caudally inclined horn core that of the living Ammodorcas clarkei and Antidorcas marsupialis. These similarities may be the result of parallel evolution, but further research is needed to explore this interesting resemblance.