遗迹化石Trichophy...统湄潭组中的首次报道及意义_张小乐.pdf

收稿日期:2022-01-05;改回日期:2022-06-22;录用日期:2022-08-26*中国科学院南京地质古生物研究所古生物学和地层学国家重点实验室(20192112)、中国地质大学(武汉)生物地质与环境地质国家重点实验室(GBL22002)、中国科学院战略性先导科技专项(XDB26000000)和国家自然科学基金(42172003)联合资助。*通讯作者:张小乐,助理研究员,e-mail: 古生物学报,61(4):603614(2022年12月)Acta Palaeontologica Sinica,61(4):603614(December 2022)研究论文 DOI:10.19800/ki.aps.2022001 遗迹化石Trichophycus在贵州仁怀下中奥陶统湄潭组中的首次报道及意义*张小乐1,2*张竹桐3 黄 璞1 王 怿1 吴荣昌1 1 现代古生物学和地层学国家重点实验室，中国科学院南京地质古生物研究所,南京 210008;2 生物地质与环境地质国家重点实验室,中国地质大学,武汉 430074;3 中国科学院大学,北京 100049 提要 遗迹化石研究对揭示奥陶纪生物大辐射事件期间,底栖生物在陆棚区定居的具体过程有重要意义。Trichophycus在寒武系奥陶系有广泛报道,但是针对其时空分布、演化轨迹、造迹生物属性和生态等的系统总结和讨论较少。本文首次在贵州仁怀地区下中奥陶统湄潭组内陆棚沉积中报道了遗迹属Trichophycus。该遗迹化石由宽的U型、平直或弯曲的潜穴管以前进式方式构成潜穴系统。底部和侧部以纵向排列的、平行或近似平行的抓痕为特征,发育后退式蹼状构造,不发育衬里。上述特征支持将其划归到T.venosus Miller,1879。湄潭组中Trichophycus可能为一类未知的节肢动物居群所建造的觅食/居住遗迹。地质历史中Trichophycus的造迹生物来自多个类群,是行为趋同的产物。作为Glossifungites遗迹相的常见分子,它的出现可能指示沉积物的初始硬结或存在较短的沉积间断。Trichophycus相对狭窄的沉积相分布区间表明它可以作为浅海固底的指相遗迹化石。作为先锋遗迹属,Trichophycus的地史分布表明,全球各板块底栖造迹生物在陆棚区的定居是不等时的。湄潭组中Trichophycus的出现,是华南扬子区奥陶纪生物大辐射事件期间,底栖造迹生物探索陆棚区生态空间的一个缩影。关键词 潜穴 “奥陶纪生物大辐射事件”古生态 古环境意义 演化轨迹 中文引用 张小乐,张竹桐,黄璞,王怿,吴荣昌,2022.遗迹化石Trichophycus在贵州仁怀下中奥陶统湄潭组中的首次报道及意义.古生物学报,61(4):603614.DOI:10.19800/ki.aps.2022001 英文引用 Zhang Xiao-le,Zhang Zhu-tong,Huang Pu,Wang Yi,Wu Rong-chang,2022.First report of Trichophycus from the LowerMiddle Ordovician Meitan Formation of Renhuai area,Guizhou and its significance.Acta Palaeonto-logica Sinica,61(4):603614.DOI:10.19800/ki.aps.2022001 First report of Trichophycus from the LowerMiddle Ordovician Meitan Formation of Renhuai area,Guizhou and its significance ZHANG Xiao-le1,2,ZHANG Zhu-tong3,HUANG Pu1,WANG Yi1,WU Rong-chang1 1 State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,China;2 State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Wuhan 430074,China;3 University of Chinese Academy of Sciences,Beijing 100049,China 604 古 生 物 学 报 61 卷 Abstract Ichnofossils provide invaluable information in understanding the process of colonization of infauna in the shallow-marine shelf settings during the Great Ordovician Biodiversification Event.The ichnofossil Trichophycus is widely reported from the Cambrian-Ordovician strata.However,only a few studies have been conducted to investigate its temporal and spatial occurrences,evolutionary paths,trace maker identy as well as its ecological features.Here,we report Trichophycus from the Lower-Middle Ordovician Meitan Formation of Renhuai area,Guizhou Province for the first time.These fossils consist of relatively wide,straight to curved,U-shaped burrow segments that are arranged in a protrusive mode.The lower and lateral surfaces of the burrows are characterized by sets of longitudinally arranged,parallel to sub-parallel striae.The burrow lacks lining and the infill shows retrusive spreite structures.These diagnostic characteristics allow an assignation to T.venosus Miller,1879,which is interpreted as a dwelling/feeding structure constructed by a colony of unknown arthropods,while the trace maker of reported Trichophycus elsewhere may come from various groups,representing behavioral convergence.Trichophycus venosus is a member of the Glossifungites ichnofacies,possibly indicating an initial induration of the sea floor or a short-lived sedimentary hiatus.The ichnofossil Trichophycus may serve as a reliable indicator of firmground in shallow-marine settings.The geological distribution of Trichophycus,a pineer ichnogenus,suggests a diachronic infaunalization in shelf settings between different blocks.Occurrence of Trichophycus in the Meitan Formation represents colonization of the shelf substrate during the Great Ordovician Biodiversification Event on the Yangtze platform,South China.Key words burrow,the Great Ordovician Biodiversification Event,paleoecology,paleoenvironmental significance,evolutionary trail SYSTEMATIC ICHNOLOGY Ichnogenus Trichophycus Miller and Dyer,1878 Diagnosis Burrow system wide,U-or L-shaped,with hair-like scratches on the bottom and side surfaces of the tunnel;lining not developed or very thin;litholo-gy of the infill similar to that of the overlying sandstone;spreite structures well-developed.Remarks The presence of scratches is highly affected by the preservation states and characteristic of the substrate.The scratches may be inconspicuous in certain circumstances.In this situation,distinguishing Trichophycus from Teichichnus Seilacher,1955,another ichnogenus whose burrows have well-developed spreite structures,could be quite tricky(Frey and Chowns,1972;Bergstrm,1976).According to Jensen(1997),Trichophycus is characterized by the common presence of vertical branches and closely arranged spreite struc-tures,while branching is seldomly observed in Teichichnus,and its spreite structures are arranged in a loose manner(Osgood,1970;Frey and Chowns,1972;Seilacher,2007;Bayet-Goll et al.,2020).The ichnoge-nus Glyphichnus Bromley and Goldring,1992