Morphology of the Upper Post Canine Complex of Pleistocene Ponginae From Vietnam—Anatomical Variability and Systematics

Objectives: To examine the morphological variability of the isolated upper post-canine teeth currently allocated to Pongo and Langsonia from northern Vietnam. To revise the taxonomy and assess the systematics of the Middle and Late Pleistocene Ponginae based on the morphological and metric variation and the identification of derived features within samples.
Materials and Methods: A series of correspondent analyses were generated against a large database of morphological (phenetic) characters scored for each tooth. Before analysis, the data was converted into a binary format. This frequently resulted in around 130 character states (variables) being analyzed.
Results: We demonstrate that in terms of morphological and metric variation, the Middle and Late Pleistocene Ponginae samples frequently fall well outside the range observed in extant Pongo pygmaeus, but also the combined range seen in Pan paniscus and P. troglodytes. Many derived features were identified among the fossil samples. We recognize three species of Langsonia from Thẩm Khuyên Cave, one being the original species named by Schwartz and colleagues, while the other two were previously considered to belong to a species and subspecies of Pongo. We recognize two new species of Pongo from the Late Pleistocene of
Làng Tráng and Kéo Lèng caves.
Discussion: We conclude that the diversity of Ponginae inhabiting this part of mainland Southeast Asia during the Middle to Late Pleistocene is part of a monophyletic Pongo clade to the exclusion of Langsonia, which we consider a primitive member of the Ponginae.