CONODONT DIVERSIFICATION IN THE ZITAI FORMATION(FLOIAN-DAPINGIAN,LATE EARLY-EARLY MID ORDOVICIAN) OF SHITAI,ANHUI PROVINCE,EAST CHINA

Based on the preliminary research of the conodonts from the Zitai Formation at Liushuting Section,Shitai County,the conodont biodiversity changes during the Floian and the Dapingian are discussed according to the conodont biozones. The Ordovician conodont radiation in the study area got its first acme during the Oepikodus evae Biozone,which was consistent with the macroevolutionary trend of brachiopods in South China. The brachiopod faunas had their first biodiversification acme in the graptolite Didymograptellus eobifidus Biozone,roughly corresponding to the middle part of the conodont Oepikodus evae Biozone. Trilobites of South China radiated much later and got their first diversity acme in the Exigraptus clavus Biozone (late Dapingian,Mid Ordovician). In contrast,the graptolites had a much earlier biodiversification trend with its first acme in the Acrograptus filiformis Biozone and Didymograptellus eobifidus Biozone on the Yangtze Platform. After the first biodiversification,the conodont diversity on the Yangtze Platform decreased gradually. Through the correlation with the sea-level fluctuation of South China Block,the authors suggest that the conodont diversity changes might be partially controlled by the sea-level fluctuations.