A Middle Eocene lowland humid subtropical “Shangri-La” ecosystem in central Tibet
Tao Su, Robert A. Spicer, Feixiang Wu, Alexander Farnsworth, Jian Huang, Cédric Del Rio, Tao Deng, Lin Ding, Wei‐Yu‐Dong Deng, Yong‐Jiang Huang, Alice C. Hughes, Lin‐Bo Jia, Jianhua Jin, Shufeng Li, Shuiqing Liang, Jia Liu, Xiaoyan Liu, Sarah C. Sherlock, Teresa E.V. Spicer, Gaurav Srivastava, He Tang, Paul J. Valdes, Teng‐Xiang Wang, Mike Widdowson, Mengxiao Wu, Yaowu Xing, Congli Xu, Jian Yang, Cong Zhang, Shitao Zhang, Xinwen Zhang, Fan Zhao, Zhe‐Kun Zhou
Abstract
Tibet's ancient topography and its role in climatic and biotic evolution remain speculative due to a paucity of quantitative surface-height measurements through time and space, and sparse fossil records. However, newly discovered fossils from a present elevation of ∼4,850 m in central Tibet improve substantially our knowledge of the ancient Tibetan environment. The 70 plant fossil taxa so far recovered include the first occurrences of several modern Asian lineages and represent a Middle Eocene (∼47 Mya) humid subtropical ecosystem. The fossils not only record the diverse composition of the ancient Tibetan biota, but also allow us to constrain the Middle Eocene land surface height in central Tibet to ∼1,500 ± 900 m, and quantify the prevailing thermal and hydrological regime. This "Shangri-La"-like ecosystem experienced monsoon seasonality with a mean annual temperature of ∼19 °C, and frosts were rare. It contained few Gondwanan taxa, yet was compositionally similar to contemporaneous floras in both North America and Europe. Our discovery quantifies a key part of Tibetan Paleogene topography and climate, and highlights the importance of Tibet in regard to the origin of modern Asian plant species and the evolution of global biodiversity.