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Scratch Traces of Large Ediacara Bilaterian Animals
- James G. Gehling, Bruce N. Runnegar, Mary L. Droser
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- Journal:
- Journal of Paleontology / Volume 88 / Issue 2 / March 2014
- Published online by Cambridge University Press:
- 15 October 2015, pp. 284-298
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Ediacara fan-shaped sets of paired scratches Kimberichnus teruzzii from the Ediacara Member of the Rawnsley Quartzite, South Australia, and the White Sea region of Russia, represent the earliest known evidence in the fossil record of feeding traces associated with the responsible bilaterian organism. These feeding patterns exclude arthropod makers and point to the systematic feeding excavation of seafloor microbial mats by large bilaterians of molluscan grade. Since the scratch traces were made into microbial mats, animals could crawl over previous traces without disturbing them. The trace maker is identified as Kimberella quadrata, whose death masks co-occur with the mat excavation traces in both Russia and South Australia. The co-occurrence of animals and their systematic feeding traces in the record of the Ediacara biota supports previous trace fossil evidence that bilaterians existed globally before the Cambrian explosion of life in the ocean.
23 - Described Taxa of Proterozoic and Selected Earliest Cambrian Carbonaceous Remains, Trace and Body Fossils
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- By Kenneth M. Towe, Smithsonian Institution, Stefan Bengtson, Uppsala Universitet, Mikhail A. Fedonkin, Palaeontological Institute, Hans J. Hofmann, University of Montreal, Carol Mankiewicz, Beloit College, Bruce N. Runnegar, University of California
- Edited by J. William Schopf, University of California, Los Angeles, Cornelis Klein, University of New Mexico
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- Book:
- The Proterozoic Biosphere
- Published online:
- 04 April 2011
- Print publication:
- 26 June 1992, pp 953-1054
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Summary
Included in this Chapter are tabulations of data on which are based discussions of Proterozoic and earliest Cambrian carbonaceous remains, trace and body fossils (Chapter 7); the Late Proterozoic–Early Cambrian evolution of metaphytes and metazoans (Chapter 8); and the Proterozoic–Early Cambrian diversification of metazoans and metaphytes (Section 11.4). Specifically, tabulations (including an evaluation of the nature and origin of the taxa and objects listed) are presented below for the following six categories of megascopic remains:
(1) Proterozoic and selected Cambrian megascopic carbonaceous films (Table 23.1);
(2) described genera and species of Proterozoic and Early Cambrian calcareous algae (Tables 23.2.1–23.2.5);
(3) taxonomically described, as well as figured but not formally described, Ediacaran (Table 23.3.1) and other Proterozoic (Table 23.3.2) metazoan body fossils;
(4) taxonomically described, as well as figured but not formally described, Proterozoic (Vendian) metazoan trace fossils (Table 23.4);
(5) genera of Late Proterozoic–Early Cambrian skeletal fossils (Table 23.5); and
(6) Proterozoic and selected Cambrian megascopic dubiofossils and pseudofossils (Table 23.6).
Proterozoic and Selected Cambrian Megascopic Carbonaceous Films
In Table 23.1 are listed, alphabetically and by year of publication, reported Proterozoic and selected Cambrian megascopic films. The conventions noted below have been used in Table 23.1.
Type code: ** = holotype of the type species of the indicated genus; * = holotype of a species other than the type species of the indicated genus.
9 - Molecular Phylogenetics, Molecular Paleontology, and the Proterozoic Fossil Record
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- By Bruce N. Runnegar, University of California, David J. Chapman, University of California, Walter M. Fitch, University of California
- Edited by J. William Schopf, University of California, Los Angeles, Cornelis Klein, University of New Mexico
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- The Proterozoic Biosphere
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- 04 April 2011
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- 26 June 1992, pp 463-486
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Summary
Twenty years ago, living microorganisms were named and classified on the basis of their morphology and physiology. This worked well for closely related taxa, but the higher level relationships between very distant lineages remained obscure because too few homologous characters were available for analysis. This situation changed dramatically in the 1980s following the invention of rapid and efficient methods for sequencing proteins and nucleic acids (both DNA and RNA). Suddenly, large numbers of homologous characters (single amino acids or single nucleotides) became available for comparison between closely and distantly related taxa. A concomitant development of computer-based methods for analyzing the new data (Section 9.2) has led to the production of “phylogenetic trees” which are designed to display, in a graphical way, the genealogical relationships between taxa at the tips of their branches. The same molecular methods have now been applied to representatives of most kinds of living organisms and they complement formal cladistic analyses based primarily upon shared-derived (synapomorphic) morphological characters.
These new methods have enabled a second approach to historical biology. The molecular comparisons may, in principle, produce information about the history of organisms with no fossil record. For example, colorful, tropical, soft-bodied molluscs known as nudibranchs are unknown as fossils. When did they first evolve? Molecular methods can provide an answer.
For Precambrian paleobiology the applications are obvious. However, the proportion of species with living descendants diminishes as one moves further backwards in time.
21 - Construction and Use of Geological, Geochemical, and Paleobiological Databases
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- By J. M. Hayes, Indiana University, Stefan Bengtson, Uppsala Universitet, Hans J. Hofmann, University of Montreal, Jere H. Lipps, University of California, Donald R. Lowe, Stanford University, Carol Mankiewicz, Beloit College, Carl V. Mendelson, Beloit College, Toby B. Moore, University of California, Bruce N. Runnegar, University of California, Harald Strauss, Ruhr-Universität Bochum
- Edited by J. William Schopf, University of California, Los Angeles, Cornelis Klein, University of New Mexico
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- The Proterozoic Biosphere
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- 04 April 2011
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- 26 June 1992, pp 855-864
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The earlier collaborative project of the PPRG (1979–1980; Schopf 1983a) used a great deal of paper. As analytical work neared completion, handwritten “scoreboards” and “hit lists” were compiled to be sure that work proceeded efficiently and that important samples were not missed. As tables of results were prepared, extensive bibliographies were developed relating to stratigraphic relationships and sedimentary ages. Participants in the project reworded the accumulating paper like so many burrowing animals. When, for example, a decision was reached about the age to be estimated for a particular rock unit, multiple tabular entries had to be changed. Much communication focused on keeping the records straight rather than on questions of interpretation.
The “personal-computer revolution” preceded the beginning of the current PPRG project. Many of the researchers involved had already developed computerized databases, and it was resolved that the power and flexibility of this technology would be applied to the sample-tracking and information-management problems of PPRG. Three problem areas were identified: (i) construction of unified bibliographic database that could be searched and which could be used for preparation of the reference list for the final publication; (ii) management of the sample inventory and laboratory work; and (iii) compilation of results and related information. Systems were eventually developed in all of these areas as described briefly below. In spite of efforts at coordination, the degree of integration initially hoped for was not achieved, principally because the databases were, in their organization a well as contents, the result of individual efforts.
8 - The Proterozoic-Early Cambrian Evolution of Metaphytes and Metazoans
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- By Stefan Bengtson, Uppsala Universitet, Jack D. Farmer, University of California, Mikhail A. Fedonkin, Palaeontological Institute, USSR Academy of Sciences, Jere H. Lipps, University of California, Bruce N. Runnegar, University of California
- Edited by J. William Schopf, University of California, Los Angeles, Cornelis Klein, University of New Mexico
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- The Proterozoic Biosphere
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- 04 April 2011
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- 26 June 1992, pp 425-462
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The fossil record of the later Proterozoic through the Early Cambrian is marked by extraordinary change. This change indicates a fundamental reorganization of the biosphere from the exclusively single-celled prokaryotic and protistan ecosystems that prevailed during much of the Proterozoic, to ecosystems characterized by complex multicellular plants and animals of the latest Proterozoic and Early Cambrian. The first recorded events in this transition took place about 900 Ma and the last about 550 Ma, a period of time exceeding that since the end of the Paleozoic. But the final and most dramatic phase, the “Cambrian Explosion,” occurred over a few tens of Ma at the onset of the Cambrian.
The glaring contrast between the Precambrian and the Phanerozoic has long been recognized as a major problem in the history of life. Darwin (1859) attempted to explain the sudden appearance of the Cambrian fauna by inadequacies of the rock record, and Walcott (1910) used a similar concept in his “Lipalian Interval” at the base of the Cambrian. Certainly the abrupt appearance in some local areas (for example, in the contact between Yudomian dolomites and Tommotian limestones in the Aldan-Lena region of Yakutia; Rozanov et al. 1969; Khomentovskij and Karlova 1986) may still be explained by incompleteness of the record.
7 - Proterozoic and Earliest Cambrian Carbonaceous Remains, Trace and Body Fossils
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- By Kenneth M. Towe, Smithsonian Institution, Stefan Bengtson, Uppsala Universitet, Mikhail A. Fedonkin, Palaeontological Institute, USSR Academy of Sciences, Hans J. Hofmann, University of Montreal, Carol Mankiewicz, Beloit College, Bruce N. Runnegar, University of California
- Edited by J. William Schopf, University of California, Los Angeles, Cornelis Klein, University of New Mexico
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- The Proterozoic Biosphere
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- 04 April 2011
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- 26 June 1992, pp 343-424
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This Chapter deals with the records of all of the Proterozoic fossil finds which are not included among the prokaryotic or protistan fossils dealt with in Chapter 5. In general, therefore, Chapter 7 deals with the earliest fossil records of higher organisms on earth. However, where systematic assignment is subject to debate there is unavoidable overlap with the prokaryotes and protists.
In historical perspective, publications describing presumed Precambrian megafossils of various kinds go back more than 100 years. Reports of carbonaceous films appeared as early as 1854 (Eichwald 1854). “Trace fossil” descriptions date from 1866 (Dawson 1866), and “body fossils” from 1872 (Billings 1872a, b). Related to the now-famous Ediacaran faunas, the first unequivocal megafossil to be described was that of Rangea schneiderhöhni reported by G. Gürich in 1930 from rocks in southwest Africa. Since these early reports, hundreds of widely, if not universally accepted Proterozoic megafossils have been described from around the world. This record of Proterozoic megafossil remains is therefore not without its share of problems which are similar to those associated with the phylogenetically lower organisms described in Chapter 5. These problems include decisions regarding biogenicity and fossil syngenicity, as well as doubts about geologic age. There are disparate taxonomic judgments, including the differing environmental and/or evolutionary interpretations such judgments may engender. In some instances the reasoning may be circular.