Fossil leaves of Berhamniphyllum(Rhamnaceae) from Markam,Tibet and their biogeographic implications  

作　　者：Zhekun ZHOU Tengxiang WANG Jian HUANG Jia LIU Weiyudong DENG Shihu LI Chenglong DENG Tao SU 

机构地区：[1]Key Laboratory of Tropical Forest Ecology,Xishuangbanna Tropical Botanical Garden,Chinese Academy of Sciences,Xishuangbanna 666303,China [2]Key Laboratory for Plant Diversity and Biogeography of East Asia,Kunming Institute of Botany,Chinese Academy of Sciences,Kunming 650204,China [3]University of Chinese Academy of Sciences,Beijing 100049,China [4]State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China [5]Lancaster Environment Centre,Lancaster University,Lancaster LA14YQ,UK

出　　处：《Science China Earth Sciences》2020年第2期224-234,共11页中国科学（地球科学英文版）

基　　金：supported by the Strategic Priority Research Program of CAS (Grant Nos. XDA2007030102 & XDB26000000);the NSFC (the National Natural Science Foundation of China)-NERC (Natural Environment Research Council of the United Kingdom) joint research program (Grant Nos. 41661134049 & NE/P013805/1);The Second Tibetan Plateau Scientific Expedition and Research Program (STEP), CAS (Grant No. 2019QZKK0705);Youth Innovation Promotion Association, CAS (Grant No. 2017439);Key Research Program of Frontier Sciences, CAS (Grant No. QYZDB-SSW-SMC016)

摘　　要：A new occurrence of buckthorn fossil leaves is reported from the upper Eocene strata of Markam Basin,southeastern Tibet,China.The leaf margin is either entire or slightly sinuous.Secondary veins are regularly spaced,forming eucamptodromous venation.These secondaries exist as straight lines from midvein to near margin and then arch abruptly upward and enter into a margin vein.The tertiary veins are densely spaced and parallel,and are percurrent to secondary veins.This leaf architecture conforms with Berhamniphyllum Jones and Dilcher,an extinct fossil genus reported from America.Our fossils are characterized by their dense secondaries,with secondary veins on the upper half portion of the blade accounting for over 40%of all secondaries.A new species,Berhamniphyllum junrongiae Z.K.Zhou,T.X.Wang et J.Huang sp.nov.,is proposed.Further analysis shows that confident assignment among Rhamnidium,Berchemia,and Karwinskia cannot be made based on leaf characters alone.Berhamniphyllum might represent an extinct common ancestor of these genera.In this study,several fossil Berchemia from Yunnan and Shandong are emended and reassigned to Berhamniphyllum.A new complex,namely the Berchemia Complex,is proposed based on morphology,molecular evidence,and the fossil record.This complex contains the fossil leaves of Rhamnidium,Karwinskia,Berchemia,and Berhamniphyllum.The historical biogeography of the Berchemia Complex is also discussed in this paper.This complex might have originated in the late Cretaceous in Colombia,South America,and dispersed to North America via Central America during the Eocene.Subsequently,the complex moved from North America to East Asia via the Bering Land Bridge no later than the late Eocene.Besides,the complex migrated from North America to Europe via the North Atlantic Land Bridge and then migrated further to Africa.In East Asia,it first appeared in Markam on the Qinghai-Tibetan Plateau,and then dispersed to other regions of Asia.A new occurrence of buckthorn fossil leaves is reported from the upper Eocene strata of Markam Basin, southeastern Tibet, China. The leaf margin is either entire or slightly sinuous. Secondary veins are regularly spaced, forming eucamptodromous venation. These secondaries exist as straight lines from midvein to near margin and then arch abruptly upward and enter into a margin vein. The tertiary veins are densely spaced and parallel, and are percurrent to secondary veins. This leaf architecture conforms with Berhamniphyllum Jones and Dilcher, an extinct fossil genus reported from America. Our fossils are characterized by their dense secondaries, with secondary veins on the upper half portion of the blade accounting for over 40% of all secondaries. A new species, Berhamniphyllum junrongiae Z. K. Zhou, T. X. Wang et J. Huang sp. nov., is proposed. Further analysis shows that confident assignment among Rhamnidium, Berchemia, and Karwinskia cannot be made based on leaf characters alone. Berhamniphyllum might represent an extinct common ancestor of these genera. In this study, several fossil Berchemia from Yunnan and Shandong are emended and reassigned to Berhamniphyllum. A new complex, namely the Berchemia Complex, is proposed based on morphology, molecular evidence, and the fossil record. This complex contains the fossil leaves of Rhamnidium, Karwinskia, Berchemia, and Berhamniphyllum. The historical biogeography of the Berchemia Complex is also discussed in this paper. This complex might have originated in the late Cretaceous in Colombia, South America,and dispersed to North America via Central America during the Eocene. Subsequently, the complex moved from North America to East Asia via the Bering Land Bridge no later than the late Eocene. Besides, the complex migrated from North America to Europe via the North Atlantic Land Bridge and then migrated further to Africa. In East Asia, it first appeared in Markam on the Qinghai-Tibetan Plateau, and then dispersed to other regions of Asia.

关 键 词：Berchemia complex Berhamniphyllum CENOZOIC Qinghai-Tibetan Plateau BIOGEOGRAPHY 

分 类 号：Q914[天文地球—古生物学与地层学]