The Proterozoic Fossil Record of Heterotrophic Eukaryotes

Porter, Susannah M.

doi:10.1007/1-4020-5202-2_1

Cited by 34 publications

(28 citation statements)

References 98 publications

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“…They may occasionally produce a wall with mineralized scales (test) that is potentially preservable, as observed in testate amoebozoans recognized in Neoproterozoic at c. 770-740 Ma (Porter, 2006), initially called the vase-shaped microfossils (Bloeser et al, 1977). They show a well-defined oral opening for exuding cytoplasm, often with a plug.…”

Section: Biological Affinity Of Dictyosphaerashuiyousphaeridium Plexusmentioning

confidence: 99%

“…The test is rigid, composed of acetolysis-resistant organic matter, and may show a reticulate surface pattern of once attached scales (Melicerion poikilon). These microfossils have been recognized as heterotrophic biota since their discovery (Bloeser, 1985;Marti-Mus and Moczydłowska, 2000;Porter and Knoll, 2000;Porter et al, 2003;Porter, 2006).…”

Section: Biological Affinity Of Dictyosphaerashuiyousphaeridium Plexusmentioning

confidence: 99%

“…Precambrian sediments preserved a relative abundance of globally distributed marine and some hydrothermal and lacustrine aquatic microorganisms that are fundamental for understanding the early evolution of life and especially the origin and diversification of eukaryotes (Mendelson et al, 1992;Javaux et al, 2004;Grey, 2005;Knoll et al, 2006;Porter, 2006;Moczydłowska, 2008;Butterfield, 2009;Lamb et al, 2009;Moczydłowska et al, 2011;Strother et al, 2011). An initial step in tracing this process is the identification of phenotypic characters, metabolic processes, and modes of life in order to recognize phylogeny of the microfossils.…”

Section: Introductionmentioning

confidence: 99%

“…Diversifications of green and red algal lineages, as well as heterotrophic protists occurred by a minimum age of 1.2 Ga, as indicated by the fossil record (Butterfield, 2000;Porter and Knoll, 2000;Porter, 2006). Single primary symbiosis and the origin of plastids that gave rise to Plantae (alternatively called Viridiplantae or Archaeplastida, Cavalier-Smith, 2003;Keeling, 2002, 2004;Baldauf, 2008) are broadly estimated by molecular clocks to have evolved by 1.5 Ga (Yoon et al, 2004;Hackett et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Affinity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China

Agić¹,

Moczydłowska²,

Yin

2015

J. Paleontol.

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Abstract.-Light microscope and scanning electron microscope observations on new material of unicellular microfossils Dictyosphaera macroreticulata and Shuiyousphaeridium macroreticulatum, from the Mesoproterozoic Ruyang Group in China, provide insights into the microorganisms' biological affinity, life cycle and cellular complexity. Gigantosphaeridium fibratum n. gen. et sp., is described and is one of the largest Mesoproterozoic microfossils recorded. Phenotypic characters of vesicle ornamentation and excystment structures, properties of resistance and cell wall structure in Dictyosphaera and Shuiyousphaeridium are all diagnostic of microalgal cysts. The wide size ranges of the various morphotypes indicate growth phases compatible with the development of reproductive cysts. Conspecific biologically, each morphotype represents an asexual (resting cyst) or sexual (zygotic cyst) stage in the life cycle, respectively. We reconstruct this hypothetical life cycle and infer that the organism demonstrates a reproductive strategy of alternation of heteromorphic generations. Similarly in Gigantosphaeridium, a metabolically expensive vesicle with processes suggests its protective role as a zygotic cyst. In combination with all these characters and from the resemblance to extant green algae, we propose the placement of these ancient microorganisms in the stem group of Chloroplastida (Viridiplantae). A cell wall composed of primary and secondary layers in Dictyosphaera and Shuiyouisphaeridium required a high cellular complexity for their synthesis and the presence of an endomembrane system and the Golgi apparatus. The plastid was also present, accepting the organism was photosynthetic. The biota reveals a high degree of morphological and cell structural complexity, and provides an insight into ongoing eukaryotic evolution and the development of complex life cycles with sexual reproduction by 1200 Ma.

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Section: Biological Affinity Of Dictyosphaerashuiyousphaeridium Plexusmentioning

confidence: 99%

Section: Biological Affinity Of Dictyosphaerashuiyousphaeridium Plexusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Affinity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China

Agić¹,

Moczydłowska²,

Yin

2015

J. Paleontol.

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“…For example, although some vaseshaped microfossils found in .742-Ma rocks have been relatively confidently identified as arcellinids (Amoebozoa), others from this assemblage could correspond to either amoebozoan or euglyphid (Rhizaria) amoebae (Porter and Knoll 2000; Porter et al 2003). Based on an apparent increase in the diversity of complex organic-walled microfossils, a number of paleontologists suggest that the diversification of most eukaryotic kingdoms occurred at 800 Ma (Porter et al 2003;Knoll et al 2006;Porter 2006;Javaux 2007;Knoll 2013). …”

Section: Calibrating Estimates Of Evolutionary Rates: Biomarkers and mentioning

confidence: 99%

On the Age of Eukaryotes: Evaluating Evidence from Fossils and Molecular Clocks

Eme

Sharpe

Brown

et al. 2014

Cold Spring Harbor Perspectives in Biology

223

155

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Our understanding of the phylogenetic relationships among eukaryotic lineages has improved dramatically over the few past decades thanks to the development of sophisticated phylogenetic methods and models of evolution, in combination with the increasing availability of sequence data for a variety of eukaryotic lineages. Concurrently, efforts have been made to infer the age of major evolutionary events along the tree of eukaryotes using fossilcalibrated molecular clock-based methods. Here, we review the progress and pitfalls in estimating the age of the last eukaryotic common ancestor (LECA) and major lineages. After reviewing previous attempts to date deep eukaryote divergences, we present the results of a Bayesian relaxed-molecular clock analysis of a large dataset (159 proteins, 85 taxa) using 19 fossil calibrations. We show that for major eukaryote groups estimated dates of divergence, as well as their credible intervals, are heavily influenced by the relaxed molecular clock models and methods used, and by the nature and treatment of fossil calibrations. Whereas the estimated age of LECA varied widely, ranging from 1007 (943-1102) Ma to 1898 (1655 -2094) Ma, all analyses suggested that the eukaryotic supergroups subsequently diverged rapidly (i.e., within 300 Ma of LECA). The extreme variability of these and previously published analyses preclude definitive conclusions regarding the age of major eukaryote clades at this time. As more reliable fossil data on eukaryotes from the Proterozoic become available and improvements are made in relaxed molecular clock modeling, we may be able to date the age of extant eukaryotes more precisely.

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