Megafossil Evidence for Ordovician/Silurian Terestrial Biotas

EAR-0308931俄亥俄大学奥陶系-志留系陆生生物的证据这项研究探索了陆地上复杂生命的起源，重点是建立第一个陆地生态系统。这项工作的重点是至少4.4亿年前居住在陆地表面的有机体化石群落，这些生物群落为陆地的殖民提供了第一个直接证据。这些群落以保存在阿巴拉契亚盆地上奥陶统和下志留统河流和三角洲沉积中的丰富碳质类生物中、巨型化石和/或共生组合为代表。标本是迄今发现的最古老的宏观陆地化石，表明最早的复杂陆地生物具有比目前所认识的更大的石化潜力。他们还证明，在这片土地上形成了一层实质性的地物，形成的时间比目前所知的要早得多。拟议研究的目标是在复杂生物对陆地的最初殖民和维管植物出现之间的关键但鲜为人知的时间段内，发展关于陆地生命的基本知识。对这些奥陶系-志留纪陆地化石的研究集中在1)记录第一个陆地群落，2)确定单个化石的形态、解剖和超微结构特征，3)开始了解这些化石生物的多样性、系统亲和力和生物相互作用。这些目标将通过实验室准备和对已经收集的化石进行特征确定来实现。这项工作是由PI以及俄亥俄大学的研究生和本科生研究人员进行的。正在通过与同事的合作进行系统的调查，这些同事要么是这些化石最有可能与之相关的活生物体的专家，要么是来自同时代地层的化石孢粉形态的专家。结果将通过出版物和在国家和国际会议上的介绍传播，并通过本科生实验室练习和在互联网数据库上张贴新的调查结果来实现更多的教育推广。

EAR-0308931MEGAFOSSIL EVIDENCE FOR ORDOVICIAN-SILURIAN TERRESTRIAL BIOTASGar W. Rothwell (EAR-0308931) Ohio UniversityABSTRACTThis research explores the origins of complex life on land, with an emphasis on establishment of the first terrestrial ecosystems. The work focuses on fossilized communities of organisms that inhabited the land surface at least 440 million years ago, and that provide the first direct evidence for colonization of the land. These communities are represented by abundant carbonaceous meso- and megafossils of thalloid organisms and/or symbiotic associations that are preserved in Upper Ordovician and Lower Silurian fluvial and deltaic deposits of the Appalachian Basin. Specimens are the oldest macroscopic terrestrial fossils ever discovered, demonstrating that the earliest complex land organisms had much greater fossilization potential than is currently recognized. They also document that a substantial ground cover of thalloid forms was established on the land far earlier than presently known. Goals of the proposed research are to develop fundamental knowledge about terrestrial life during the crucial but poorly known time interval between initial colonization of land by complex organisms and the emergence of vascular plants. Investigations of these Ordovician-Silurian terrestrial fossils focus on 1) documenting the first land communities, 2) determining the morphological, anatomical and ultrastructural characters of individual fossils, and 3) beginning to develop an understanding of the diversity, systematic affinities, and biological interactions of the fossilized organisms. These goals will be achieved through laboratory preparations and character determinations for fossils that already have been collected. The work is being conducted by the PI, and by graduate and undergraduate student researchers at Ohio University. Systematic investigations are being pursued through collaborations with colleagues who are experts on either the living organisms to which the fossils are most likely related, or on fossil palynomorphs from contemporaneous strata. Results will be disseminated by publications and presentations at national and international meetings, with additional educational outreach being achieved through undergraduate student laboratory exercises, and by posting of the new findings on internet data bases.