Showing papers by "James D. Schiffbauer published in 2011"

Microbial biofilms and the preservation of the Ediacara biota

Abstract: Laflamme, M., Schiffbauer, J.D., Narbonne, G.M., & Briggs, D.E.G. 2011: Microbial biofilms and the preservation of the Ediacara biota. Lethaia, Vol. 44, pp. 203–213. The terminal Neoproterozoic Ediacaran Period is typified by the Ediacara biota (ca. 579–542 Ma), which includes the first morphologically complex macroscopic organisms. Both the taphonomic setting that promoted the preservation of the soft-bodied Ediacara biota in coarse-grained sediments, and the influence of associated microbial coatings on this process, have generated debate. Specimens of Ediacaran discs (Aspidella) from the Fermeuse Formation of Newfoundland, Canada, were analysed using environmental scanning electron microscopy (ESEM) and focused ion beam electron microscopy (FIB-EM) to determine the relationship between the fossil specimens and the surrounding sediment. The presence of chemically distinct (Al–Mg–Fe–K- and to a lesser extent S-rich), finer-grained sediment (with organized iron sulphides) surrounding the upper and lower margins of the Ediacaran fossils is consistent with elemental analyses of well preserved bacterial biofilms from other localities. ESEM analyses reveal a contrast in the composition of the sediment bound within the discs, which contains a higher concentration of Al, Ca and K, and the purer Si-rich sediment that forms the surrounding matrix. This suggests that the coarse grained sediment was incorporated into the organism during life. Ediacaran discs were likely surrounded by a bacterial biofilm or thin microbial mat composed primarily of extracellular polymeric substances (or exopolysaccharide) during life, which added structural stability to these frond holdfasts, and facilitated their fossilization. Microbially mediated preservation in Fermeuse-style Ediacaran taphonomy provides an explanation for the dominance of Aspidella holdfasts in these settings, and suggests that preservation of Ediacaran fossils in the round may be much more prevalent than previously recognized. We suggest that the overwhelming dominance of circular to bulbous forms such as Aspidella in Ediacaran biotas around the world is a direct result of the interplay between microbial ecology and microbially mediated taphonomy. □Aspidella, Ediacaran preservation, environmental scanning electron microscopy, focused ion beam electron microscopy, palaeoecology, taphonomic bias.

Taphonomic study of Ediacaran organic-walled fossils confirms the importance of clay minerals and pyrite in Burgess Shale−type preservation

Abstract: Burgess Shale−type (BST) macrofossils and organic-walled microfossils are preserved as carbonaceous compressions and may share similar taphonomic processes. Previous taphonomic investigations of carbonaceous compressions have primarily focused on the microchemistry of Cambrian BST fossils, but comparative data from organic-walled microfossils were not available. To address these issues, we analyzed two organic-walled taxa from the Yangtze Gorges area of the South China block, Chuaria (an acritarch) and Vendotaenia (a ribbon-shaped fossil). Their abundance offers the opportunity for destructive microanalysis, including petrography, electron microscopy, and elemental mapping on both bedding planes and in cross sections. Our data suggest that Chuaria preservation is remarkably similar to BST fossils in that its vesicle walls are closely associated with clay minerals. In addition, like many BST macrofossils, Chuaria and Vendotaenia are also closely associated with pyrite; Chuaria vesicles are often filled with framboidal pyrite, and Vendotaenia fossils are associated with sulfate, partly derived from pyrite oxidation. The comparative taphonomy of Chuaria and Vendotaenia and BST macrofossils indicates that the preservation of organic-walled acritarchs may be aided by clay and pyrite mineralization, and that these abundant microfossils may serve as proxies for uncovering in more detail the taphonomic histories of BST preservation.

Quantifying the evolution of early life

Abstract: Quantifying the evolution of early life , Quantifying the evolution of early life , کتابخانه مرکزی دانشگاه علوم پزشکی تهران

Quantifying the evolution of early life : numerical approaches to the evaluation of fossils and ancient ecosystems

Abstract: PART I: NUMERICAL METHODS 1. Ordination methods and the evaluation of Ediacaran communities Matthew E. Clapham. 2. Exploratory Multivariate Techniques and their Utility for Understanding Ancient Ecosystems John W. Huntley 3. Morphometrics in the Study of Ediacaran Fossil Forms Marc Laflamme and Michelle M. Casey. 4. Analyzing Predation from the Dawn of the Phanerozoic Lindsey R. Leighton 5. Ecospace Utilization during the Ediacaran Radiation and the Cambrian Eco-plosion Andrew M. Bush, Richard K. Bambach, and Douglas H. Erwin 6. Quantifying Bioturbation in Ediacaran and Cambrian Rocks Katherine N. Marenco and David J. Bottjer 7. Assessing the role of skeletons in Early Paleozoic carbonate production: Insights from Cambro-Ordovician strata, western Newfoundland Sara B. Pruss and Hannah Clemente 8. Exploring the Ecological Dynamics of Extinction Amelinda E. Webb and Lindsey R. Leighton 9. Fossils with Little Relief - Using Lasers to Conserve, Image, and Analyse the Ediacara biota Jonathan B. Antcliffe and Martin D. Brasier PART II: TECHNOLOGICAL APPROACHES 10. Confocal laser scanning microscopy and Raman (and fluorescence) spectroscopic imagery of permineralized Cambrian and Neoproterozoic fossils J. William Schopf and Anatoliy B. Kudryavtsev 11. X-ray microanalysis of Burgess Shale and similarly preserved fossils Patrick J. Orr and Stuart Kearns 12. Ultrastructural Approaches to the Microfossil Record: Assessing Biological Affinities by use of Transmission Electron Microscopy Sebastian Willman and Phoebe A. Cohen 13. Paleobiological applications of focused ion beam electron microscopy (FIB-EM): An ultrastructural approach to the (micro)fossil record James D. Schiffbauer and Shuhai Xiao 14. Reconstructing deep-time biology with molecular fossils Christian Hallmann, Amy Kelly, S. Neal Gupta, and Roger E. Summons 15. Carbon and Sulfur Stable Isotopic Systems and Their Application in Paleoenvironmental Analysis Kathleen A. McFadden and Amy E. Kelly 1. Ordination methods and the evaluation of Ediacaran communities Matthew E. Clapham. 2. Exploratory Multivariate Techniques and their Utility for Understanding Ancient Ecosystems John W. Huntley 3. Morphometrics in the Study of Ediacaran Fossil Forms Marc Laflamme and Michelle M. Casey. 4. Analyzing Predation from the Dawn of the Phanerozoic Lindsey R. Leighton 5. Ecospace Utilization during the Ediacaran Radiation and the Cambrian Eco-plosion Andrew M. Bush, Richard K. Bambach, and Douglas H. Erwin 6. Quantifying Bioturbation in Ediacaran and Cambrian Rocks Katherine N. Marenco and David J. Bottjer 7. Assessing the role of skeletons in Early Paleozoic carbonate production: Insights from Cambro-Ordovician strata, western Newfoundland Sara B. Pruss and Hannah Clemente 8. Exploring the Ecological Dynamics of Extinction Amelinda E. Webb and Lindsey R. Leighton 9. Fossils with Little Relief - Using Lasers to Conserve, Image, and Analyse the Ediacara biota Jonathan B. Antcliffe and Martin D. Brasier PART II: TECHNOLOGICAL APPROACHES 10. Confocal laser scanning microscopy and Raman (and fluorescence) spectroscopic imagery of permineralized Cambrian and Neoproterozoic fossils J. William Schopf and Anatoliy B. Kudryavtsev 11. X-ray microanalysis of Burgess Shale and similarly preserved fossils Patrick J. Orr and Stuart Kearns 12. Ultrastructural Approaches to the Microfossil Record: Assessing Biological Affinities by use of Transmission Electron Microscopy Sebastian Willman and Phoebe A. Cohen 13. Paleobiological applications of focused ion beam electron microscopy (FIB-EM): An ultrastructural approach to the (micro)fossil record James D. Schiffbauer and Shuhai Xiao 14. Reconstructing deep-time biology with molecular fossils Christian Hallmann, Amy Kelly, S. Neal Gupta, and Roger E. Summons 15. Carbon and Sulfur Stable Isotopic Systems and Their Application in Paleoenvironmental Analysis Kathleen A. McFadden and Amy E. Kelly

Paleobiological Applications of Focused Ion Beam Electron Microscopy (FIB-EM): An Ultrastructural Approach to the (Micro)Fossil Record

Abstract: Coupled dual-beam focused ion beam electron microscopy (FIB-EM) has gained popularity across multiple disciplines over the past decade. Widely utilized as a stand-alone instrument for micromachining and metal- or insulator-deposition in numerous industries, the sub-μm-scale ion milling and integrated electron imaging capabilities of such FIB-based systems are well documented in the materials science literature. These capacities make FIB-EM a powerful tool for in-situ site-specific preparation of ultrathin foils for transmission electron microscopy. Recent advancements in the field-emission guns of FIB-EM systems have ­provided spatial resolution comparable to that of many high-grade scanning ­electron microscopes, providing enhanced imaging capacities with material-­deposition and material-removal capabilities. Recently, FIB-EM preparation techniques have been applied to geological samples to characterize mineral inclusions, grain boundaries, and microfossils. We here provide a summary of recent paleobiological studies that use FIB-EM methodology for the examination of fossils. Additionally, we demonstrate a novel method for analyzing the three-dimensional ultrastructure of microfossils (reported previously by Schiffbauer and Xiao [Palaios 24: 616–626, 2009]). This method, FIB-EM nanotomography, consists of sequential ion milling, or cross-sectioning, and concurrent SEM imaging, a technique that provides three-dimensional data of precise sites at high spatial resolution, yielding new insight into fossil ultrastructure. We here illustrate the use of FIB-EM nanotomography by studies of herkomorphic and acanthomorphic acritarchs (organic-walled microfossils) extracted from the ≥999 Ma Mesoproterozoic Ruyang Group of North China. The three-dimensional characteristics of important but controversial acritarch ­features such as extravesicular processes and vesicularly enclosed central bodies are described. Taken together, these case studies demonstrate that FIB-EM ­instruments are powerful and useful tools for investigating the three-dimensionality of microfossil ultra- and nanostructures.