Ediacaran Fauna Precursors to the Cambrian Explosion Matt Cox

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

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

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. The Ediacaran Fauna represents the oldest collection of metazoan fossils on the planet, commencing in the fossil record around 610 mya. Geneticists however, 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) "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) More recent studies have taken more factors into account and point towards a more recent divergence, sometime around 570 mya (Peterson, et al)

Morphology Over 30 genera described Over 30 genera described 4 main types found 4 main types found Most abundant are circular impressions, believed to be benthic dwellers like sea anemones (explaining their abundance) 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) 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. 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. Least abundant are the “sea-fronds”, although they are represented in all major finds.

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

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

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

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. 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. By 580 mya, representatives of the major phyla found in the Cambrian explosion can be found swimming in the Precambrian seas.

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

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

References Woodmorappe, John. "The Cambrian Explosion Remains an Enigma for Organic Evolution: The Ediacaran Fauna: Much Ado about Lichens?" Revolution Against Evolution. 5 June Nov Woodmorappe, John. "The Cambrian Explosion Remains an Enigma for Organic Evolution: The Ediacaran Fauna: Much Ado about Lichens?" Revolution Against Evolution. 5 June Nov "Vendian: Localities." University of California Museum of Paleontology. 18 Nov "Vendian: Localities." University of California Museum of Paleontology. 18 Nov "Ediacara Biota." Queens University Geology Department. 20 Apr Queens University. 18 Nov "Ediacara Biota." Queens University Geology Department. 20 Apr Queens University. 18 Nov "Australia Before Time." Australian Heritage Commission. 18 Nov "Australia Before Time." Australian Heritage Commission. 18 Nov Clowes, Chris. "The Ediacaran (Vendian)." The Palaeos Project Nov Clowes, Chris. "The Ediacaran (Vendian)." The Palaeos Project Nov Yarrington, Kate. "Ediacara Assembalge." Fossil Lagerstatten. University of Bristol. 18 Nov Yarrington, Kate. "Ediacara Assembalge." Fossil Lagerstatten. University of Bristol. 18 Nov University Of California - Riverside. "Dating Our Ancestors: Study Suggests Macroscopic Bilaterian Animals Did Not Appear Until 555 Million Years Ago." ScienceDaily 30 September November University Of California - Riverside. "Dating Our Ancestors: Study Suggests Macroscopic Bilaterian Animals Did Not Appear Until 555 Million Years Ago." ScienceDaily 30 September November Peterson, Kevin J, et al. "Estimating Metazoan Divergence Times with a Molecular Clock." Proceedings of the National Academy of Sciences (Apr. 2004). Peterson, Kevin J, et al. "Estimating Metazoan Divergence Times with a Molecular Clock." Proceedings of the National Academy of Sciences (Apr. 2004).