Possible animal-body fossils in pre-Marinoan limestones from South Australia

Maloof, Adam C.; Rose, Catherine; Beach, Robert; Samuels, Bradley M.; Calmet, Claire; Erwin, Douglas H.; Poirier, Gerald; Yao, Nan; Simons, Frederik J.

doi:10.1038/ngeo934

Cited by 193 publications

(116 citation statements)

References 32 publications

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“…Paleontological evidence for high levels of dissolved organic matter in deep Ediacaran oceans is equivocal (Halverson et al, 2009), as is fossil evidence for larger animals at that time (e.g. Maloof et al, 2010). Capture of prey would be best achieved by filtration and concentration of food, which favours the idea of a filter/suspension feeder arising before the evolution of complex nervous systems.…”

Section: Ecology Of Ediacaran Seas Sponge Function and Behaviourmentioning

confidence: 99%

Elements of a ‘nervous system’ in sponges

Leys

2015

Journal of Experimental Biology

128

123

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Genomic and transcriptomic analyses show that sponges possess a large repertoire of genes associated with neuronal processes in other animals, but what is the evidence these are used in a coordination or sensory context in sponges? The very different phylogenetic hypotheses under discussion today suggest very different scenarios for the evolution of tissues and coordination systems in early animals. The sponge genomic 'toolkit' either reflects a simple, pre-neural system used to protect the sponge filter or represents the remnants of a more complex signalling system and sponges have lost cell types, tissues and regionalization to suit their current suspensionfeeding habit. Comparative transcriptome data can be informative but need to be assessed in the context of knowledge of sponge tissue structure and physiology. Here, I examine the elements of the sponge neural toolkit including sensory cells, conduction pathways, signalling molecules and the ionic basis of signalling. The elements described do not fit the scheme of a loss of sophistication, but seem rather to reflect an early specialization for suspension feeding, which fits with the presumed ecological framework in which the first animals evolved.

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Section: Ecology Of Ediacaran Seas Sponge Function and Behaviourmentioning

confidence: 99%

Elements of a ‘nervous system’ in sponges

Leys

2015

Journal of Experimental Biology

128

123

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“…One of the earliest lines of evidence for sponges comes from well-preserved molecular biomarkers of demosponges from strata of the Neoproterozoic Huqf Supergroup of the South Oman Salt Basin pre-dating the termination of the Marinoan glaciation and having a minimum age of c. 635 Ma (McCaffrey et al 1994;Love et al 2006Love et al , 2009. Fossils interpreted as sponge-grade metazoans are also found in the pre-Marinoan Trezona Formation of South Australia with a maximum age of 659.7 ± 5.3 Ma (Maloof et al 2010c). Palaeophragmodictya reticulata Gehling & Rigby, 1996, from the Ediacaran Rawnsley Quartzite in South Australia, was interpreted as a hexactinellid (Gehling & Rigby, 1996;Debrenne & Reitner, 2001), or a stem-group sponge (Mehl, 1998), but later it was reinterpreted as an attachment disc of a problematic organism of uncertain affinity to sponges or cnidarians (Serezhnikova, 2007).…”

Section: A Sponges and Spongiomorphsmentioning

confidence: 99%

Chronology of early Cambrian biomineralization

et al. 2011

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-Data on the first appearances of major animal groups with mineralized skeletons on the Siberian Platform and worldwide are revised and summarized herein with references to an improved carbon isotope stratigraphy and radiometric dating in order to reconstruct the Cambrian radiation (popularly known as the 'Cambrian explosion') with a higher precision and provide a basis for the definition of Cambrian Stages 2 to 4. The Lophotrochozoa and, probably, Chaetognatha were first among protostomians to achieve biomineralization during the Terreneuvian Epoch, mainly the Fortunian Age. Fast evolutionary radiation within the Lophotrochozoa was followed by radiation of the sclerotized and biomineralized Ecdysozoa during Stage 3. The first mineralized skeletons of the Deuterostomia, represented by echinoderms, appeared in the middle of Cambrian Stage 3. The fossil record of sponges and cnidarians suggests that they acquired biomineralized skeletons in the late Neoproterozoic, but diversification of both definite sponges and cnidarians was in parallel to that of bilaterians. The distribution of calcium carbonate skeletal mineralogies from the upper Ediacaran to lower Cambrian reflects fluctuations in the global ocean chemistry and shows that the Cambrian radiation occurred mainly during a time of aragonite and high-magnesium calcite seas.

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“…Molecular data has thus given us a rich picture of what we expect to find in the fossil record. However, the search for early metazoans has thus far been limited to biomarkers from 711-635 Ma rocks in Oman (Love et al 2008) and various fossils of uncertain taxonomic affinity (e.g., Maloof et al 2010). It is possible that other fossils categorized here as non metazoan eukaryotes actually represent early branching or stem metazoans but are unrecognizable as such.…”

Section: Diversity Patterns In Relation To Ecological Factorsmentioning

confidence: 99%

The Proterozoic Record of Eukaryotes

2015

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Abstract.-Proterozoic strata host evidence of global "Snowball Earth" glaciations, large perturbations to the carbon cycle, proposed changes in the redox state of oceans, the diversification of microscopic eukaryotes, and the rise of metazoans. Over the past half century, the number of fossils described from Proterozoic rocks has increased exponentially. These discoveries have occurred alongside an increased understanding of the Proterozoic Earth system and the geological context of fossil occurrences, including improved age constraints. However, the evaluation of relationships between Proterozoic environmental change and fossil diversity has been hampered by several factors, particularly lithological and taphonomic biases. Here we compile and analyze the current record of eukaryotic fossils in Proterozoic strata to assess the effect of biases and better constrain diversity through time. Our results show that mean within assemblage diversity increases through the Proterozoic Eon due to an increase in high diversity assemblages, and that this trend is robust to various external factors including lithology and paleogeographic location. In addition, assemblage composition changes dramatically through time. Most notably, robust recalcitrant taxa appear in the early Neoproterozoic Era, only to disappear by the beginning of the Ediacaran Period. Within assemblage diversity is significantly lower in the Cryogenian Period than in the preceding and following intervals, but the short duration of the nonglacial interlude and unusual depositional conditions may present additional biases. In general, large scale patterns of diversity are robust while smaller scale patterns are difficult to discern through the lens of lithological, taphonomic, and geographic variability.

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Possible animal-body fossils in pre-Marinoan limestones from South Australia

Cited by 193 publications

References 32 publications

Elements of a ‘nervous system’ in sponges

Elements of a ‘nervous system’ in sponges

Chronology of early Cambrian biomineralization

The Proterozoic Record of Eukaryotes

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