Podocarpium is an extinct genus of the legume family with a rich fossil record in Eurasia, dating back to the Eocene. However, the lack of fossil records in some key areas, such as the Tibetan Plateau, makes knowledge of the species diversity and biogeographic evolution of the genus far from sufficient.
The Paleoecological Research Group has long carried out paleontological research in the central Part of the Qinghai-Tibet Plateau, and in recent years, a new flora, the Xiongmei Flora, has been discovered in the Neo-Tsuruga Formation on the Lunpola Basin. The fossils of the pod fruit found in it were studied, and a new species was established through numerical analysis of morphology and geometric morphology: Tibetan single-seed bean Podocarpium tibeticum W.-C. Li, J. Huang et T. Su sp. Nov, which distinguishes it from the published fossil species of the genus Monoseed bean, is characterized by asymmetry on both sides of the pod, an eagle’s beak, and a significant tilt at the base of the fruit.
Tibetan single seed beans are the earliest fossil record of the genus on the Tibetan Plateau to date, and this discovery suggests that the genus already existed in the central Tibetan Plateau in the Late Eocene (35 Ma). Through a comprehensive analysis of fossil evidence and model simulations, it is suggested that the genus may have originated in East Asia, spread to the central valley of Tibet in the late Eocene, and then spread westward to Europe along the island chain of the Neo-Tethys Ocean through low-latitude paths; The distribution pattern of the genus over geological periods is closely related to the history of global climate change. The findings further support the central Tibetan Plateau as an important hub for global Paleogene flora exchanges.
Figure 1. Appearance of the fossil point of the male plum flora
Figure 2. A new fossil of the genus Monoseed bean found in the Lunpola Basin of Tibet – Tibetan single-seed bean Podocarpium tibeticum; Restoration of the genus Monoseed bean A. P. tibeticum sp.nov.; B. P. eocenicum; C. P. podocarpum.
Figure 3. Analysis of fruit shape principal components and shape variation of single-seeded bean genus
The results were published in the international paleobotanical journal Review of Palaeobotany and titled “Podocarpium (Fabaceae) from the late Eocene of central Tibetan Plateau and its biogeographic implication.” Palynology celebrates the ninetieth birthday of Academician Zhou Zhiyan, a famous paleobotanist in China. Li Wei, a master’s student of the Paleoecology Group, became the first author, and researcher Su Tao and associate researcher Huang Jian were the co-corresponding authors of the paper. The results have been funded by the Strategic Pilot Research Program of the Chinese Academy of Sciences, the National Natural Science Foundation of China, the Second Comprehensive Scientific Expedition to the Tibetan Plateau of the Chinese Academy of Sciences, the Youth Innovation Promotion Association of the Chinese Academy of Sciences and the Natural Science Foundation of Yunnan Province. (Source: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences)
Related paper information:https://doi.org/10.1016/j.revpalbo.2022.104745