Cambrian trilobite Ovatoryctocara granulata Tchernysheva,1962 and its biostratigraphic significance

作     者：Jinliang Yuan a,Yuanlong Zhao b,Jin Peng b,Xuejian Zhu a,Jih-pai Lin c a Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,East Beijing Road 39,Nanjing 210008,China b College of Resource and Environment Science,Guizhou University,Guiyang 550003,China c School of Earth Sciences,Ohio State University,Columbus,OH 43210,USA 

作者机构：Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences East Beijing Road 39 Nanjing 210008 China College of Resource and Environment Science Guizhou University Guiyang 550003 China School of Earth Sciences Ohio State University Columbus OH 43210 USA 

出 版 物：《Progress in Natural Science:Materials International》 (自然科学进展·国际材料(英文))

年 卷 期：2009年第19卷第2期

页      面：213-221页

核心收录：

学科分类：070903[理学-古生物学与地层学(含：古人类学)] 0709[理学-地质学] 07[理学] 

基　　金：supported by the National Natural Science Foundation of China (Grant Nos.40672018,40762001) the Foundation of the Mobile Project of Science and Technology of Guizhou Province (Grant No.Gui Ji.2007-4004) the Foundation of the Governor of Guizhou Province (GuiE.2006-7) the Key Project of International Cooperation of Guizhou Science and Technology (Gui.co.G.2008-700110) the Major Basic Research Projects of MST of China (2006CB80640) 

主　　题：Trilobites Ovatoryctocara granulata Tchernysheva,1962 Cambrian Biostratigraphy 

摘      要：The genus Ovatoryctocara Tchernysheva,1962,and its key species Ovatoryctocara granulata Tchernysheva,1962,are revised. Ovatoryctocara granulata occurs near the base of the Ovatoryctocara Zone and ranges up into the lower portion of the Kounamkites Zone in the Siberian Platform. O. granulata also appears in southeastern Guizhou,South China,but O. granulata in northern Greenland may represent an indefinite species. Specimens of Ovatoryctocara from Newfoundland cannot be identified to species level. Specimens includ-ing two cranidia and three pygidia from the lower part of the Aoxi Formation at Yaxi Village,Shizhu Town,eastern Tongren,north-eastern Guizhou,were previously assigned to O. granulata,which is now reassigned as a new species O. yaxiensis sp. nov. It bears the following main features: glabella club-shaped,slightly expanded medially,with four pairs of lateral furrows,of which S1-S3 are trian-gular pits,S4 is shallow,connecting with axial furrow; shorter palpebral lobe situated a little anterior to the midway of facial suture across the fixigenae,longer posterolateral area (exsag.); semielliptical pygidium consisting of seven axial rings with a terminal piece and with eight pairs of marginal tips giving a sawtooth-like shape of the lateral margins in dorsal view. Although O. granulata is a widely distributed species,the FAD of O. granulata,for a global stage boundary,still has some disadvantages. First,its distribution is not as wide as that of Oryctocephalus indicus (Reed,1910). Second,specimens of O. granulata are common only in Siberia. Third,the strati-graphic range of the species has not been studied in detail in all continents. Fourth,O. granulata is relatively small and easily affected by post-burial distortion. Last but not least,there exists obviously a facies change between the Ovatoryctocara Zone (lower Amgan Stage; deeper water facies) and the underlying Anabaraspis splendens Zone (Toyonian Stage; shallow water facies) in Siberian Platform. Nev-ert