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THE JURASSIC MENTOUGOU-YUDAISHAN FLORA FROM WESTERN YANSHAN,NORTH CHINA

Chen Fen Yang Guan-xiu (Wuhan College of Geology) Dou Ya-wei (Regional Geological Surveting Team,Xinjiang)  
The present paper deals with the florafrom the Mentougou group in the West Hillsof Beijing (Peking) and the Yudaishangroup in Xiahuayuan,Hebei.The Mentou-gou-Yudaishan flora may be attributed to theConiopteris-Phoenicopsis flora of Sze (1956),and is characterized by the following com-ponents.1) Ferns predominant:Coniopterishymenophylloides,C.tatungensis,C.burejen-sis,Eboracia lonifolia,Cladophlebis asiatics(=Cl.haiburensis) (with large-sized pinnules),Raphaelia,Clathropteris and Hausmannia.2) Ginkgophytes abundant:Ginkgo,Ginkgoites,Baiera,Sphenobaiera,Czekanow-skia and Phoenicopsis.3) Conifers well-represented:Podoza-mites,Pityophyllum and Elatocladus.4) Cycadophytes also represented:Ano-mozamites,Nilssonia,Pterophyllum andCtenis.Besides,three genera belonging to Equi-setales,Equisetites,Neoealamites and Annula-riopsis,and rare Lycoposid,Lycopodites,alsooccur.This flora may be subdivided into threeassemblages representing three horizons.Thelower assemblage contains such old forms asEquisetites with broad stems and Balera bear-ing narrow segments,while the upper as-semblage bears some new elements,such asConiopteris burejensis,Cladophlebis delica-tula,Raphaelia prinadai,Pseudocycas pecten,in addition to the wood Xenoxylon hopeienseChang (1929) and Protopiceoxylon exstinctumGothan (Mathews et Ho,1945).As to the age of the flora,we suggest thatthe lower assemblage may be referred toLower—Middle Jurassic,the middle assemblageto Middle Jurassic and the upper assemblageprobably to Middle—Upper Jurassic.
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