Dental shape evolution of the giant panda ( Ailuropoda , Ursidae) during the Quaternary

The giant panda is well known to have unique dentition, adapted to bamboo exclusive diet. The teeth are used to cut and grind the bamboo. However, it is unclear how these teeth evolved through geographical time. Here, we present the first geometric morphometric analysis of all cheek teeth of the giant panda, based on the large fossil collection of the giant panda teeth found from the Pleistocene deposits of southern China. Our analyses reveal the substantial intraspecific variation of the giant panda teeth, but no significant interspecific differences in Ailuropoda, supporting the basic function of the giant panda teeth has already formed since the Early Pleistocene. Among the cheek teeth, the premolars show the highest interspecific variation, suggesting a continuous increase in the feeding efficiency of the bamboo diet, which may facilitate the giant panda to grow a larger body size from Early Pleistocene species to A. melanoleuca. The Late Pleistocene A. m. baconi and two modern two subspecies show largely overlapped morphospace for all teeth, and the variation ranges are also similar, suggesting a fully established feeding apparatus and implying a similar diet. Our analyses provide new information on the giant panda evolution and adaptation.