Oligocene Ailanthus from northwestern Qaidam Basin, northern Tibetan Plateau, China and its implications

Abstract

As the largest inland basin in the northeastern Tibetan Plateau, Qaidam Basin has traditionally been thought of as the key region to study the Cenozoic climatic changes in the plateau; however, the information from a palaeobotanic respect is still lacking because of the paucity of the fossil plants. Fossil fruits and foliage of Ailanthus (Simaroubaceae) are reported from the Oligocene Shangganchaigou Formation in the northwestern Qaidam Basin, Qinghai Province, China. All the characters suggest that the fossil materials should be assigned to A. confucii, which is one widely distributed fossil species in the Cenozoic, regarded as the analogue of extant A. altissima. Current materials represent the first fossil record of Simaroubaceae in the northern Tibetan Plateau. Based on the climate requirements of the living A. altissima, the ranges of mean annual temperature (MAT) and mean annual precipitation (MAP) reflected by current fossils from Qaidamare 6.9–17.0°C, and 376–1,383 mm, respectively, compared with the current climate at the fossil site with MAT of −1.03°C and MAP of 60.5 mm. The results indicate that the climate conditions of the fossil site during the Early Oligocene were much warmer and more humid than that of the current. We hereby suggest the warm and moist air could approach the northwestern Qaidam and to accommodate the ecological environment in Early Oligocene.

Fossil samaras of Ailanthus from South China and their phytogeographic implications

“…The fossil fruits from South China are the samaroid mericarps with a centrally located single seed and stylar scar with main ventral veins on one side of the samara. These characteristics are unique features of the genus Ailanthus , which make it easily distinguishable from the winged fruits of other plants ( Su et al., 2013 ; Liu et al., 2019 ; Yang et al., 2021 ).…”

“…Throughout the Eocene, this genus spread across Asia, Europe, and North America ( MacGinitie, 1969 ; Grande, 1984 ; Collinson, 1988 ; Manchester, 1990 ; Akhmetiev, 1993 ; Fields, 1996 ; Wilf, 2000 ). From the Oligocene to Miocene, Ailanthus became distributed widely on all continents in the Northern Hemisphere ( Tanai and Suzuki, 1963 ; WGCPC, 1978 ; Zhilin, 1967 ; Mai, 1995 ; He and Tao, 1997 ; Meyer and Manchester, 1997 ; Manchester, 2001 ; Teodoridis et al., 2015 ; Martinetto and Macaluso, 2018 ; Liu et al., 2019 ; Yang et al., 2021 ). Hence, it seems from this evidence that the genus originated in western North America or eastern Asia during the early Eocene and subsequently diversified in Europe and East Asia ( Figure 2 ).…”

“…Ailanthus is widely recorded in Cenozoic deposits across the Northern Hemisphere ( Corbett and Manchester, 2004 ; Su et al., 2013 ; Song et al., 2014 ; Liu et al., 2019 ; Yang et al., 2021 ). Samaroid mericarps of Ailanthus are easily recognized in the fossil record based on their morphological characters, which include a samara with a seed situated in the center, as well as the main ventral vein and style scar being on the same side of the seed ( Nooteboom, 1962 ; Corbett and Manchester, 2004 ).…”

“…A. tardensis was reported from the Oligocene of Ningming, Guangxi Province ( Corbett and Manchester, 2004 ; Song et al., 2014 ), and A. maximus was described from the middle Eocene of Jianglang and upper Eocene of Dayu and Nima, central Tibetan Plateau ( Liu et al., 2019 ; Su et al., 2020 ; Xiong et al., 2022 ). A. confucii is the most widely distributed species known from the lower-middle Eocene of Fushun, Liaoning Province ( WGCPC, 1978 ; Corbett and Manchester, 2004 ), the lower Oligocene of Wenshan, Yunnan Province ( Su et al., 2013 ; Tian et al., 2021 ), the Qaidam Basin, northeastern Qinghai-Tibetan Plateau, Qinghai Province ( Yang et al., 2021 ), the Oligocene of Ningming, Guangxi Province ( Song et al., 2014 ), and the Miocene of Linqi ( WGCPC, 1978 ; Corbett and Manchester, 2004 ) and Shanwang, Shandong Province ( Tanai and Suzuki, 1963 ; Sun et al., 1999 ; Corbett and Manchester, 2004 ). Despite abundant Ailanthus fossils at the middle latitudes of the Northern Hemisphere, there are still only a few fossil records from low-latitude areas.…”

Introduction to NECLIME Special Issue: Biodiversity and floral patterns in the course of Cenozoic climate change

“…In the paper by Yang et al (2021), the authors describe Oligocene Ailanthus from the Northwestern Qaidam Basin indicating that climatic conditions prevailing at the fossil site during the Early Oligocene were much warmer and more humid than at present.…”