Cédric Del Rio1,2, Teng-Xiang Wang1,3, Jia Liu1,2, Shui-Qing Liang1,4, Robert A Spicer1,5, Fei-Xiang Wu6, Zhe-Kun Zhou1,2,7, Tao Su1,2,3. 1. CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, 666303, China. 2. Center of Conservation Biology / Economic Botany / Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Mengla, 666303, China. 3. University of Chinese Academy of Sciences, Beijing, 100049, China. 4. Public Technology Service Center, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, 666303, China. 5. School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes, MK7 6AA, UK. 6. Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthro- pology, Chinese Academy of Sciences, Beijing, 100044, China. 7. Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China.
Abstract
PREMISE: Apocynaceae is common in the fossil record, especially as seed remains from the Neogene of Europe and North America, but rare in Asia. Intrafamilial assignment is difficult due to the lack of diagnostic characters, and new fossil and modern data are needed to understand the paleobiogeography of this group. METHODS: We studied three Apocynaceae seed impressions from the Lower Eocene Niubao Formation, Jianglang village, Bangor County, central Qinghai-Tibetan Plateau. Morphological data from living and fossil species were phylogenetically mapped to enable systematic assignment. RESULTS: We describe a new genus, Asclepiadospermum gen. nov., and two new species, A. marginatum sp. nov. and A. ellipticum sp. nov. These species are characterized by an elliptical seed, a margin surrounding the central part of the seed, and polygonal, irregular, and small epidermal cells, and differ mainly in terms of the size of the margin and the shape of the apex. All these characters indicate that this new genus belongs to the subfamily Asclepiadoideae (Apocynaceae). CONCLUSIONS: These fossils represent the earliest fossil seed records of Asclepiadoideae. Asclepiadospermum indicates a humid tropical to subtropical flora during the early Eocene in central Tibet. Moreover, our discoveries indicate a close floristic connection between Eurasia and Africa during the early Eocene, which expands our knowledge of the floristic linkage between Tibet and other regions at that time.
PREMISE: Apocynaceae is common in the fossil record, especially as seed remains from the Neogene of Europe and North America, but rare in Asia. Intrafamilial assignment is difficult due to the lack of diagnostic characters, and new fossil and modern data are needed to understand the paleobiogeography of this group. METHODS: We studied three Apocynaceae seed impressions from the Lower Eocene Niubao Formation, Jianglang village, Bangor County, central Qinghai-Tibetan Plateau. Morphological data from living and fossil species were phylogenetically mapped to enable systematic assignment. RESULTS: We describe a new genus, Asclepiadospermum gen. nov., and two new species, A. marginatum sp. nov. and A. ellipticum sp. nov. These species are characterized by an elliptical seed, a margin surrounding the central part of the seed, and polygonal, irregular, and small epidermal cells, and differ mainly in terms of the size of the margin and the shape of the apex. All these characters indicate that this new genus belongs to the subfamily Asclepiadoideae (Apocynaceae). CONCLUSIONS: These fossils represent the earliest fossil seed records of Asclepiadoideae. Asclepiadospermum indicates a humid tropical to subtropical flora during the early Eocene in central Tibet. Moreover, our discoveries indicate a close floristic connection between Eurasia and Africa during the early Eocene, which expands our knowledge of the floristic linkage between Tibet and other regions at that time.
Authors: Xinwen Zhang; Uriel Gélin; Robert A Spicer; Feixiang Wu; Alexander Farnsworth; Peirong Chen; Cédric Del Rio; Shufeng Li; Jia Liu; Jian Huang; Teresa E V Spicer; Kyle W Tomlinson; Paul J Valdes; Xiaoting Xu; Shitao Zhang; Tao Deng; Zhekun Zhou; Tao Su Journal: Nat Commun Date: 2022-07-01 Impact factor: 17.694