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Ediacaran Fauna

Ediacaran Fauna. Precursors to the Cambrian Explosion Matt Cox. Period of existence. Proterozoic Era 650 – 543 million years ago Worldwide distribution. Disagreement.

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Ediacaran Fauna

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  1. Ediacaran Fauna Precursors to the Cambrian Explosion Matt Cox

  2. Period of existence • Proterozoic Era • 650 – 543 million years ago • Worldwide distribution

  3. Disagreement • Stephen Jay Gould and Adolf Seilacher propose that the ediacaran fauna are where “failed experiments” in the evolution of multi-cellular animals • University of Oregon paleontologist Gregory Retallack believes that the ediacaran fauna were actually lichens. • Typical opinion today seems to be that a mix of cnidarians, fungi, and sponges were dominant in the ediacaran.

  4. The Oldest Fossils ≠ The Oldest Animals • The Ediacaran Fauna represents the oldest collection of metazoan fossils on the planet, commencing in the fossil record around 610 mya. • Geneticists however, • "Calibrated rates of molecular sequence divergence were used to test this hypothesis. Seven independent data sets suggest that invertebrates diverged from chordates about a billion years ago, about twice as long ago as the Cambrian. Protostomes apparently diverged from chordates well before echinoderms, which suggests a prolonged radiation of animal phyla." (Wray, Levinton, Shapiro) • More recent studies have taken more factors into account and point towards a more recent divergence, sometime around 570 mya (Peterson, et al)

  5. Morphology • Over 30 genera described • 4 main types found • Most abundant are circular impressions, believed to be benthic dwellers like sea anemones (explaining their abundance) • Next most common are simple burrows made by bilaterian animals (whether or not they were made by annelids is not known) • Third are other benthic forms, some of which suggest affinities with annelids, arthropods, and echinoderms. Others in this group are bizarre enough to be problematic and unknown. • Least abundant are the “sea-fronds”, although they are represented in all major finds.

  6. Major Finds: Mistaken Point • Newfoundland, Canada • Volcanic ash dated to 565 mya • Oldest complex ediacaran fossils accurately dated • The fossils found here have sometimes been assigned to a completely different kingdom of multi-cellular organisms

  7. Winter Coast, Russia • Contains the largest and most diverse collection of ediacaran fossils.

  8. Ediacara Hills, Australia • In Eastern Australia, the locale of the first precambrian fossil finds.

  9. Extinction • There appears to have been a major extinction event at the boundary between the Precambrian and the Cambrian Explosion (around 545 mya). Some ediacaran representatives survive, but most go extinct. • By 580 mya, representatives of the major phyla found in the Cambrian explosion can be found swimming in the Precambrian seas.

  10. Extinction Continued • Presumably, the survivors of this extinction represented the taxonomic groups in the Cambrian Explosion.

  11. Conclusions • Ediacaran fauna were all soft bodied • Led to the evolution of predators • At one point, coexisted with phlya represented in the Cambrian Explosion. • Not much known about what caused the extinction of the Ediacaran Fauna.

  12. References • Woodmorappe, John. "The Cambrian Explosion Remains an Enigma for Organic Evolution: The Ediacaran Fauna: Much Ado about Lichens?" Revolution Against Evolution. 5 June 1999. 18 Nov. 2007     <http://www.rae.org/cambrian.html>. • "Vendian: Localities." University of California Museum of Paleontology. 18 Nov. 2007     <http://www.ucmp.berkeley.edu/vendian/vendianloc.html>. • "Ediacara Biota." Queens University Geology Department. 20 Apr. 2000. Queens University. 18 Nov.     2007 <http://geol.queensu.ca/museum/exhibits/ediac/ediac.html>. • "Australia Before Time." Australian Heritage Commission. 18 Nov. 2007 <http://www.ahc.gov.au/     publications/geofossil/ediacara.html>. • Clowes, Chris. "The Ediacaran (Vendian)." The Palaeos Project. 2002. 18 Nov. 2007     <http://www.palaeos.com/Proterozoic/Neoproterozoic/Ediacaran/Ediacaran.htm>. • Yarrington, Kate. "Ediacara Assembalge." Fossil Lagerstatten. University of Bristol. 18 Nov. 2007     <http://palaeo.gly.bris.ac.uk/palaeofiles/lagerstatten/Ediacara/flora%20and%20fauna.htm>. • University Of California - Riverside. "Dating Our Ancestors: Study Suggests Macroscopic Bilaterian Animals Did Not Appear Until 555 Million Years Ago." ScienceDaily 30 September 2002. 18 November 2007 <http://www.sciencedaily.com­ /releases/2002/09/020927064725.htm>. • Peterson, Kevin J, et al. "Estimating Metazoan Divergence Times with a Molecular Clock."     Proceedings of the National Academy of Sciences 101.17 (Apr. 2004).

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