Ediacaran FaunaEdiacaran Fauna

Precursors to the Cambrian Precursors to the Cambrian ExplosionExplosion

Matt Matt CoxCox

Period of existencePeriod of existence Proterozoic EraProterozoic Era 650 – 543 million years ago650 – 543 million years ago Worldwide distributionWorldwide distribution

DisagreementDisagreement

Stephen Jay Gould and Adolf Seilacher Stephen Jay Gould and Adolf Seilacher propose that the ediacaran fauna are propose that the ediacaran fauna are where “failed experiments” in the where “failed experiments” in the evolution of multi-cellular animalsevolution of multi-cellular animals

University of Oregon paleontologist University of Oregon paleontologist Gregory Retallack believes that the Gregory Retallack believes that the ediacaran fauna were actually lichens.ediacaran fauna were actually lichens.

Typical opinion today seems to be that a Typical opinion today seems to be that a mix of cnidarians, fungi, and sponges mix of cnidarians, fungi, and sponges were dominant in the ediacaran.were dominant in the ediacaran.

The Oldest Fossils ≠ The The Oldest Fossils ≠ The Oldest AnimalsOldest Animals

The Ediacaran Fauna represents the oldest The Ediacaran Fauna represents the oldest collection of metazoan fossils on the planet, collection of metazoan fossils on the planet, commencing in the fossil record around 610 mya.commencing in the fossil record around 610 mya.

Geneticists however,Geneticists however, "Calibrated rates of molecular sequence divergence "Calibrated rates of molecular sequence divergence

were used to test this hypothesis. Seven independent were used to test this hypothesis. Seven independent data sets suggest that invertebrates diverged from data sets suggest that invertebrates diverged from chordates about a billion years ago, about twice as long chordates about a billion years ago, about twice as long ago as the Cambrian. Protostomes apparently diverged ago as the Cambrian. Protostomes apparently diverged from chordates well before echinoderms, which from chordates well before echinoderms, which suggests a prolonged radiation of animal phyla." (Wray, suggests a prolonged radiation of animal phyla." (Wray, Levinton, Shapiro)Levinton, Shapiro)

More recent studies have taken more factors into More recent studies have taken more factors into account and point towards a more recent divergence, account and point towards a more recent divergence, sometime around 570 mya (Peterson, et al)sometime around 570 mya (Peterson, et al)

MorphologyMorphology Over 30 genera describedOver 30 genera described 4 main types found4 main types found

Most abundant are circular impressions, believed to be Most abundant are circular impressions, believed to be benthic dwellers like sea anemones (explaining their benthic dwellers like sea anemones (explaining their abundance)abundance)

Next most common are simple burrows made by Next most common are simple burrows made by bilaterian animals (whether or not they were made by bilaterian animals (whether or not they were made by annelids is not known)annelids is not known)

Third are other benthic forms, some of which suggest Third are other benthic forms, some of which suggest affinities with annelids, arthropods, and echinoderms. affinities with annelids, arthropods, and echinoderms. Others in this group are bizarre enough to be Others in this group are bizarre enough to be problematic and unknown. problematic and unknown.

Least abundant are the “sea-fronds”, although they are Least abundant are the “sea-fronds”, although they are represented in all major finds.represented in all major finds.

Major Finds: Mistaken Major Finds: Mistaken PointPoint

Newfoundland, CanadaNewfoundland, Canada Volcanic ash dated to 565 myaVolcanic ash dated to 565 mya Oldest complex ediacaran fossils accurately Oldest complex ediacaran fossils accurately

dateddated The fossils found here have sometimes been The fossils found here have sometimes been

assigned to a completely different kingdom of assigned to a completely different kingdom of multi-cellular organismsmulti-cellular organisms

Winter Coast, RussiaWinter Coast, Russia

Contains the largest and most Contains the largest and most diverse collection of ediacaran diverse collection of ediacaran fossils.fossils.

Ediacara Hills, AustraliaEdiacara Hills, Australia

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

ExtinctionExtinction

There appears to have been a major There appears to have been a major extinction event at the boundary extinction event at the boundary between the Precambrian and the between the Precambrian and the Cambrian Explosion (around 545 mya). Cambrian Explosion (around 545 mya). Some ediacaran representatives survive, Some ediacaran representatives survive, but most go extinct.but most go extinct.

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

Extinction ContinuedExtinction Continued

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

ConclusionsConclusions

Ediacaran fauna were all soft bodiedEdiacaran fauna were all soft bodied Led to the evolution of predatorsLed to the evolution of predators At one point, coexisted with phlya At one point, coexisted with phlya

represented in the Cambrian represented in the Cambrian Explosion.Explosion.

Not much known about what caused Not much known about what caused the extinction of the Ediacaran the extinction of the Ediacaran Fauna.Fauna.

ReferencesReferences Woodmorappe, John. "The Cambrian Explosion Remains an Enigma for Organic Woodmorappe, John. "The Cambrian Explosion Remains an Enigma for Organic

Evolution: The Ediacaran Fauna: Much Ado about Lichens?" Evolution: The Ediacaran Fauna: Much Ado about Lichens?" Revolution Against Revolution Against EvolutionEvolution. 5 June 1999. 18 Nov. 2007     <http://www.rae.org/cambrian.html>. . 5 June 1999. 18 Nov. 2007     <http://www.rae.org/cambrian.html>.

"Vendian: Localities." "Vendian: Localities." University of California Museum of PaleontologyUniversity of California Museum of Paleontology. 18 Nov. . 18 Nov. 2007     <http://www.ucmp.berkeley.edu/vendian/vendianloc.html>. 2007     <http://www.ucmp.berkeley.edu/vendian/vendianloc.html>.

"Ediacara Biota." "Ediacara Biota." Queens University Geology DepartmentQueens University Geology Department. 20 Apr. 2000. Queens . 20 Apr. 2000. Queens University. 18 Nov.     2007 University. 18 Nov.     2007 <http://geol.queensu.ca/museum/exhibits/ediac/ediac.html>. <http://geol.queensu.ca/museum/exhibits/ediac/ediac.html>.

"Australia Before Time." "Australia Before Time." Australian Heritage CommissionAustralian Heritage Commission. 18 Nov. 2007 . 18 Nov. 2007 <http://www.ahc.gov.au/     publications/geofossil/ediacara.html>. <http://www.ahc.gov.au/     publications/geofossil/ediacara.html>.

Clowes, Chris. "The Ediacaran (Vendian)." Clowes, Chris. "The Ediacaran (Vendian)." The Palaeos ProjectThe Palaeos Project. 2002. 18 Nov. . 2002. 18 Nov. 2007     <http://www.palaeos.com/Proterozoic/Neoproterozoic/Ediacaran/2007     <http://www.palaeos.com/Proterozoic/Neoproterozoic/Ediacaran/Ediacaran.htm>. Ediacaran.htm>.

Yarrington, Kate. "Ediacara Assembalge." Yarrington, Kate. "Ediacara Assembalge." Fossil LagerstattenFossil Lagerstatten. University of Bristol. . University of Bristol. 18 Nov. 2007     <http://palaeo.gly.bris.ac.uk/palaeofiles/lagerstatten/Ediacara/flora18 Nov. 2007     <http://palaeo.gly.bris.ac.uk/palaeofiles/lagerstatten/Ediacara/flora%20and%20fauna.htm>. %20and%20fauna.htm>.

University Of California - Riverside. "Dating Our Ancestors: Study Suggests University Of California - Riverside. "Dating Our Ancestors: Study Suggests Macroscopic Bilaterian Animals Did Not Appear Until 555 Million Years Ago." Macroscopic Bilaterian Animals Did Not Appear Until 555 Million Years Ago." ScienceDailyScienceDaily 30 September 2002. 18 November 2007 <http://www.sciencedaily.com 30 September 2002. 18 November 2007 <http://www.sciencedaily.com /releases/2002/09/020927064725.htm>. /releases/2002/09/020927064725.htm>.

Peterson, Kevin J, et al. "Estimating Metazoan Divergence Times with a Molecular Peterson, Kevin J, et al. "Estimating Metazoan Divergence Times with a Molecular

Clock."     Clock."     Proceedings of the National Academy of SciencesProceedings of the National Academy of Sciences 101.17 (Apr. 2004). 101.17 (Apr. 2004).