Eukaryotic organisms in Proterozoic oceans

By Andrew H. Knoll, E. Javaux, D. Hewitt, Phoebe A. Cohen. Philosophical Transactions of the Royal Society B: Biological Sciences, 2006

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The geological record of protists begins well before the Ediacaran and Cambrian diversification of animals, but the antiquity of that history, its reliability as a chronicle of evolution and the causal inferences that can be drawn from it remain subjects of debate. Well-preserved protists are known from a relatively small number of Proterozoic formations, but taphonomic considerations suggest that they capture at least broad aspects of early eukaryotic evolution. A modest diversity of problematic, possibly stem group protists occurs in ca 1800–1300 Myr old rocks. 1300–720 Myr fossils document the divergence of major eukaryotic clades, but only with the Ediacaran–Cambrian radiation of animals did diversity increase within most clades with fossilizable members. While taxonomic placement of many Proterozoic eukaryotes may be arguable, the presence of characters used for that placement is not. Focus on character evolution permits inferences about the innovations in cell biology and development that underpin the taxonomic and morphological diversification of eukaryotic organisms.

Subfields: Atmospheric Science, Molecular Biology, Paleontology

View Paper: https://www.semanticscholar.org/paper/399924cf140e4b1cb8290a0dbc86bc2ab6b84c48

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Citations in the corpus

Proterozoic phytoplankton and timing of Chlorophyte algae origins (2011, background): “Knoll et al. (2006) considered this species to be an actively growing life stage of heterotrophic eukaryote, yet without any specific attribution.”
Cyanobacterial evolution during the Precambrian (2016, background): “Fossil evidence supports the presence of bacteria long before the origin of eukaryotes (Knoll et al. 2006; Schopf 2006; Wacey et al. 2011; Sugitani et al. 2013).”
The naked planet Earth: Most essential pre-requisite for the origin and evolution of life (2013, background): “…for Cambrian explosion has long been traditionally ascribed to the increased oxygen content in atmosphere (Rye and Holland,1998; Holland, 2006; Knoll et al., 2006), from less than 10 2 to 1 PAL, because high oxygen pressure is necessary to keep the reaction to produce collagen that paste…”
The Multiple Origins of Complex Multicellularity (2011, background): “Despite this, complex multicellularity, as defined here, occurs only in the Eukarya.”
Estimating the timing of early eukaryotic diversification with multigene molecular clocks (2011, background): “Fossils provide minimum dates, leaving open the possibility that clades evolved much earlier than their first fossil appearance (2, 31).”
The Microalgal Cell (2013, background): “The origin of eukaryotes is not precisely known, but may have occurred about 2 billion years ago (Knoll et al., 2006).”
The Evolution of Multicellularity: A Minor Major Transition? (2007, background): “Multicellular eukaryotes may have existed 1 billion years ago (Knoll et al. 2006), but a major burst of metazoan diversification occurred about 600–700 Mya, at a time of dramatic increases in atmospheric and oceanic oxygen (Carroll 2001, King 2004, Knoll 2003, Maynard Smith & Szathmáry 1995,…”
The Proterozoic Record of Eukaryotes (2015, methodology): “Due to their complex external morphological structure, these fossils can confidently be assigned to groupswithin the Eukarya including metazoans, microalgae, and possibly fungi as well (Knoll et al. 2006; Yin et al. 2007; Moczydłowska et al. 2009; Cohen et al. 2009).”
The terrestrial biota prior to the origin of land plants (embryophytes): a review of the evidence (2015, methodology): “Knoll et al. (2006) pointed out, however, that the primary diversification of species within the eukaryotic supergroups was delayed in marine settings until about 850–720 Ma.”
The case for a Neoproterozoic Oxygenation Event: Geochemical evidence and biological consequences (2011, background): “The first green algae (and possibly lichen) emerged around this time (Porter, 2004; Knoll et al., 2006) and would have revolutionized weathering and the global carbon cycle once they made it to land (Heckman et al., 2001; Lenton and Watson, 2004).”
The Weng'an biota and the Ediacaran radiation of multicellular eukaryotes (2014, neutral): “[7-9].”