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Evidence and significance of eukaryotic diversification in the ∼1800 million-year-old Changzhougou Formation, North China.

机译：华北约18亿年历史的常州沟组真核生物多样性的证据和意义。

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摘要

The evolution of cellular complexity is both an exciting and contentious topic in paleobiological research. Traditionally, the Mesoproterozoic has been considered the time of major eukaryote diversification; however, evidence suggests that origin of eukaryotic clades occurred earlier. Recognizing eukaryotic microfossils and understanding eukaryote diversification patterns in pre-Phanerozoic rocks is based in part upon morphological characters (e.g., acritarch processes) that are either not abundant or not present in the early parts of the Proterozoic Era. Regardless if the paucity of these features is due to preservational issues or if it predates their evolution, new and refined approaches are required to understand the earliest branching patterns of the Eukarya on the tree of life.;The research herein focuses on fossils and fossil-like structures from the ∼1800 Ma Changzhougou Formation (Yanshan Range), North China. Chapter II describes how macroscopic compression-like structures can be misinterpreted as compressions of a biogenic origin. Carbonaceous compressions farther upsection in the Changcheng Group (∼1600-1800 Ma) are more promising, but are not the focus of this thesis.;Pangjiapu locality acritarchs (Changzhougou Formation) described and discussed in Chapters III and IV show that microscopic fossils in the lowermost Changcheng Group lend better insight into eukaryotic diversification. Although previous research at Pangjiapu (e.g., Yan, 1991) provided inflated estimates of eukaryotic diversity, examination of original specimens, along with acritarchs extracted by refined palynological techniques, indicates that at least 13 distinct eukaryotic morphotypes are present in the Changzhougou Formation. This assessment is based upon the following factors: primary shape, number of wall-layers, vesicle flexibility, and size. The revised eukaryotic diversity is about five times less than the original report by Yan (1991), yet it still upholds that at least a modest number of taxa from the Domain Eukarya were already present by ∼1800 Ma.;Further technological improvements of alternate analyses (e.g., biomarker, TEM, Focused Ion Beam Electron Microscopy) will continue to improve our understanding of early eukaryotes; nevertheless, this study clearly demonstrates that transmitted light study of acritarchs will continue to be an invaluable aspect of understanding and updating our knowledge of the diversification patterns of early eukaryotes.
机译：细胞复杂性的演变是古生物学研究中一个令人兴奋且充满争议的话题。传统上，中古生代被认为是主要的真核生物多样化时期。然而，有证据表明，真核进化枝起源较早。识别前生代岩石中的真核微化石和了解真核生物的多样化模式部分是基于元古代时代初期不丰富或不存在的形态特征（例如，尖顶状突）。无论这些特征的稀缺性是由于保存问题还是在其发展之前就已经存在，都需要采用新的和完善的方法来了解Eukarya在生命树上的最早分支模式。本文的研究重点是化石和化石-相似的结构来自华北地区〜1800年的马常州沟组（燕山山脉）。第二章描述了宏观压缩样结构如何被误解为生物起源的压缩。长城组（约1600-1800 Ma）的碳质压缩更上端是更有前途的，但不是本文的重点。在第三和第四章中描述和讨论的庞家堡地方性尖晶石（常州沟组）表明，该区的微观化石。最底层的长城集团更好地洞察了真核生物的多样性。尽管庞家堡以前的研究（例如Yan，1991）提供了对真核生物多样性的夸大估计，但对原始标本以及通过精细的孢粉学技术提取的雌蕊的检查表明，常州沟组至少存在13种不同的真核生物形态型。该评估基于以下因素：主要形状，壁层数，囊泡柔韧性和大小。修改后的真核生物多样性比Yan（1991）的原始报告少大约五倍，但仍然坚持到1800 Ma为止至少已经存在适度数量的来自Eukarya域的分类单元;对替代分析的进一步技术改进（例如生物标记物，TEM，聚焦离子束电子显微镜）将继续增进我们对早期真核生物的了解；但是，这项研究清楚地表明，对阿联酋的轻度研究将继续是了解和更新我们对早期真核生物多样化模式的了解的宝贵方面。

著录项

  • 作者

    Lamb, David Michael.;

  • 作者单位

    University of California, Santa Barbara.;

  • 授予单位 University of California, Santa Barbara.;
  • 学科 Geology.;Paleontology.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 123 p.
  • 总页数 123
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;古生物学;
  • 关键词

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