THE DISCOVERY OF PODOCARPIUM FROM THE MIOCENE OF QAIDAM BASIN AND ITS BIOGEOGRAPHIC IMPLICATION
Podocarpium is an extinct genus of the family Fabaceae that was widely distributed in the Eurasian continent during Cenozoic.But the lack of fossil evidence from key regions and critical time points limits the understanding of its evolutionary and distributional history.In this study,we focus on the Middle Miocene Podocarpium of the Naoge section in the Qaidam Basin,located in the northeastern of the Tibetan Plateau.By integrating global fossil records from the Cenozoic,this paper provides a comprehensive overview of the biogeographical history of the genus and discusses how environmental changes influenced its evolution,based on accurately dated specimens from the Tibetan Plateau.The Naoge section is located about 43 km south of Gahai Town,Delingha City,in the northeastern of the Qaidam Basin,with a thickness of approximately 3300 meters.Exposed are the Upper Cretaceous Quanyagou Formation,the Miocene to Pliocene Lower Youshashan Formation,Upper Youshashan Formation,and the Shizigou Formation.The fossil specimens in this study were collected from the Upper Youshashan Formation of the section,at an elevation of 2100 meters,within greenish-gray muddy siltstone.According to paleomagnetic dating,the geological age of the fossil layer is approximately 11 Ma.Our results show that the well-preserved fossil fruits and leaves of the Podocarpium podocarpum were described from the Middle Miocene of the Qaidam Basin,northeast Tibetan Plateau.Furthermore,fossil records from the Tibetan Plateau indicate that the genus had its highest diversity during the Miocene,with a distribution pattern synchronous with global trends,supporting the possibility that the Podocarpium spread and dispersed via low-latitude routes.Thus,global aridification and cooling are unlikely to be the primary causes of the range contraction of the Podocarpium.Instead,further uplift of certain areas of the Tibetan Plateau after the Miocene,by altering precipitation patterns,which may have contributed to the reduction of the Podocarpium's distribution in inland Asia.
万方数据
维普
