TEM evidence for eukaryotic diversity in mid-Proterozoic oceans

Authors

  • EMMANUELLE J. JAVAUX,

    Corresponding author
    1. Department of Astrophysics, Geophysics and Oceanography, University of Liège, Sart-Tilman 4000 Liège, Belgium
      Corresponding author: Dr Emmanuelle J. Javaux. Tel.: 32 4 366 9763; fax: 32 4 366 9746; e-mail: ej.javaux@ulg.ac.be
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  • ANDREW H. KNOLL,

    1. Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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  • MALCOLM R. WALTER

    1. Australian Centre for Astrobiology, Macquarie University, Sydney, NSW 2109, Australia
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Corresponding author: Dr Emmanuelle J. Javaux. Tel.: 32 4 366 9763; fax: 32 4 366 9746; e-mail: ej.javaux@ulg.ac.be

ABSTRACT

Biomarker molecular fossils in 2770 Ma shales suggest that the Eucarya diverged from other principal domains early in Earth history. Nonetheless, at present, the oldest fossils that can be assigned to an extant eukaryotic clade are filamentous red algae preserved in ca. 1200 Ma cherts from Arctic Canada. Between these records lies a rich assortment of potentially protistan microfossils. Combined light microscopy, scanning electron microscopy, and transmission electron microscopy on 1500-1400 Ma fossils from the Roper Group, Australia, and broadly coeval rocks from China show that these intermediate assemblages do indeed include a moderate diversity of eukaryotic remains. In particular, preserved cell wall ultrastructure, observed using transmission electron microscopy (TEM), can help to bridge the current stratigraphic gap between the unambiguous eukaryotic morphologies of later Proterozoic assemblages and molecular biomarkers in much older rocks.

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