Journal of Systematics and Evolution

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  • 收稿日期:2020-06-17 接受日期:2020-10-20

New Eocene fossil fruits and leaves of Menispermaceae from the central Tibetan Plateau and their biogeographic implications

Cédric Del Rio1,2, Jian Huang1,2, Ping Liu1, Wei-Yu-Dong Deng1,2,3, Teresa E.V. Spicer1, Fei-Xiang Wu4,5, Zhe-Kun Zhou1,2,6, and Tao Su1,2*   

  1. 1CAS Key Laboratory of Tropical Forest Ecology, Chinese Academy of Sciences, Mengla, Yunnan 666303, China

    2Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Mengla 666303, China

    3University of Chinese Academy of Sciences, Beijing 100049, China

    4Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China

    5Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Beijing 100101, China

    6Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China

  • Received:2020-06-17 Accepted:2020-10-20

Abstract:

Menispermaceae are a pantropical and temperate family with an extensive fossil record during the Paleogene, especially in North America and Europe, but with much less evidence from Asia. The latest fossil evidence indicates a succession of tropical to sub-tropical flora on the central Tibetan Plateau during the Paleogene. However, the biogeographic histories of these floras are still unresolved. Here, we report on endocarps and leaves of Menispermaceae from the Middle Eocene of Jianglang village, Bangor County, central Tibetan Plateau. The endocarps belong to two genera: Stephania which is characterized by a horseshoe-shaped endocarp and with one lateral crest ornamented by spiny to rectangular ribs, and a condyle area; Cissampelos has two characteristic lateral ridges and a conspicuous external condyle. Associated leaves belong to the genus Menispermites, and are characterized by actinodromous primary venation, brochidodromous secondary veins, entire margins, and the presence of marginal secondary veins. The biogeographic history of Menispermaceae is complex, but evidence from these new fossils indicates an early diversification of the group in Asia, probably in response to the warming climate during the Eocene. The Jianglang flora appears to be part of a boreotropical flora, connecting Asia with North American and European floras during the Middle Eocene. The modern distribution of Menispermaceous taxa found in Jianglang, as well as other families represented in the Jianglang flora, show that a tropical to sub-tropical climate occurred during the Eocene in central Tibet.

Key words: Tibetan Plateau, endocarp, leaf, fossil plant, paleobotany