Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess...

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Radiation and Evolution of Metazoans: The Cambrian Explosion and the Burgess Shale Fossils Geology 331, Paleontology

Transcript of Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess...

Page 1: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Radiation and Evolution of Metazoans: The Cambrian

Explosion and the Burgess Shale Fossils

Geology 331, Paleontology

Page 2: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Marshall, 2006

Page 3: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Halkierids, which produced some of the small, shelly fossils of the Early Cambrian

Page 4: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

More examples of small shelly fossils from the Early Cambrian. Scale bars are 0.1 mm.

Page 5: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.
Page 6: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.
Page 7: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

The Cambrian “Explosion” of Life

• What is the Cambrian “Explosion”?• Is it a true explosion of phyla, or was there a

“slow fuse” back into the Proterozoic?• Why did so many new phyla appear at this

time? Hox genes hold the answer.

Page 8: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

www.evogeneao.com/tree.html

The Tree of Life

Page 9: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Diploblastic Animals: Two Tissue Layers

Triploblastic Animals: Three Tissue Layers

Mesoderm in blue(jelly)

Page 10: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Deuterostomes (mouth is second opening during development)

Protostomes (mouth is first opening during development)

Prothero, 2007

Triploblasts: Bilaterians, protostomes & deuterostomes

Diploblasts:VendozoansCtenophora Cnidaria

Page 11: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

http://www.evolution-textbook.org/content/free/figures/10_EVOW_Art/16_EVOW_CH10.jpg

The Cambrian Explosion is among the Triploblastic Bilateria

Page 12: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Burgess Shale Fossils

• Most are soft-bodied fossils, a very rare kind of fossilization.

• Of today’s 32 living phyla, 15 are found in the Burgess Shale. The other 17 are microscopic or too delicate to be preserved.

• Another 10 extinct phyla are also found in the Burgess Shale.

Page 13: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Burgess Shale Fossils

• Assume that all 32 living phyla were alive in the Middle Cambrian.

• Add the 10 extinct phyla for a total of 42 phyla. That’s more phyla than today!

• Thus, Cambrian phyla were more diverse than today.

Page 14: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

A Paradox

• There were more body plans (phyla) near the start of animal life than today.

• However, there were many fewer species.

• This doesn’t match the expectation of slow evolutionary diversification of life.

Page 15: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Traditional Hypothesis of slowly increasing diversity.

New Hypothesis of rapidly increasing diversity followed by pruning and later diversification.

Page 16: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

The Pattern of Animal Evolution

• Initial radiation of phyla.• Reduction by natural selection.• No new phyla since the Cambrian.• Diversification within remaining phyla.

Page 17: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

A Hypothesis

• The genome of early animals was less rigid, not as “hardwired” as later animals. Adaptive mutations were more possible.

• A wide variety of body plans were produced by mutations.

• Natural selection eliminated some of these body plans.

Page 18: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

A Hypothesis

• Body plans that survived became the modern phyla.

• 500 m.y. of evolution has made genomes more rigid and more species rich.

• Mutations required to make a new body plan would be lethal. Phyla were locked in.

Page 19: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

The Burgess Shale of British Columbia: record of the Cambrian Explosion

Page 20: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Mt. Stephen in Yoho National Park, Canada

Page 21: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Geologists at the Burgess Shale quarry

Page 22: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Charles Walcott, Smithsonian Institution Geologist, at the Burgess Shale Quarry, ~ 1910

Page 23: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Paleontologist collecting a slab of fossils

Page 24: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Trilobites with preserved legs and antennae

Page 25: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

The strange animals of the Middle Cambrian Burgess Shale

Page 26: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Opabinia and Amwiskia, representatives of two extinct phyla

Page 27: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Opabinia

Page 28: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Burgess Shale worm Ottoia

Page 29: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

A spiny “worm,” Wiwaxia

Page 30: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Hallucigenia, a spiny lobopod

Which way up?

Page 31: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Hallucigenia, a new interpretation

Nature, 6/24/2015

Page 32: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Specimens of lobopods

Page 33: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Living and fossil lobopods

Page 34: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Early crustacean from the Burgess Shale, Canadapsis

Page 35: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

The first sea scorpion on the attack!

Page 36: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

The sea scorpion Sidneyia

Page 37: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Marella, extinct class of arthropods

Page 38: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Marella as Cambrian road

kill (or a squished bug?)

Page 39: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Yohoia, an extinct class of arthropods

Page 40: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Anomalocaris, the largest predator of the Cambrian. Is it an extinct phylum, or a proto-arthropod?

Page 41: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Ordovician filter-feeding anomalocarid

Nature, 2015doi:10.1038/nature14256

Page 43: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

http://www.livescience.com/14320-largest-sea-predators-fossils.html

Page 44: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Anomalocaris with a trilobite snack

Page 45: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Trilobite with a bite mark, possibly from Anomalocaris

Page 46: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.
Page 47: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Postscript: Some of the ‘new’ phyla of the Burgess Shale are now thought to be various proto-arthropods, or stem-arthropods. Thus, are these new phyla or

should we amend the definition of the Phylum Arthropoda?

PalaeontologyVolume 57, Issue 3, pages 457-468, 18 MAR 2014 DOI: 10.1111/pala.12105http://onlinelibrary.wiley.com/doi/10.1111/pala.12105/full#pala12105-fig-0004

Page 48: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

So, where did all these different body plans come from?

And, when did the Cambrian Explosion actually start?

Page 49: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

http://www.evolution-textbook.org/content/free/figures/10_EVOW_Art/16_EVOW_CH10.jpg

Page 50: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Hox genes determine the head to tail anatomy of animals. Vertebrates have 4 sets, but their Hox genes are almost identical to those of insects. Mutations in

Hox genes create new body plans or phyla.

http://www.pbs.org/wgbh/evolution/library/03/4/l_034_04.html Genetic Tool Kit: Hox genes

Page 51: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.
Page 52: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

The molecular clock is a technique in molecular evolution that uses fossil data and rates of molecular change to deduce the time in geologic history when two species or other taxa diverged. It is used to estimate the time of occurrence of speciation (lineage splitting). The molecular data used for such calculations is usually differences in nucleotide sequences for DNA or amino acid sequences for proteins.

Molecular Paleobiology

Page 53: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Substitutions are random, so there is a strong correlation with time.

Molecular Clocks

Page 54: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Detailed stage-level depiction of the animal fossil record as compared to the molecular divergence estimates for 13 different animal lineages.

D H Erwin et al. Science 2011;334:1091-1097

Some newer molecular studies push metazoan origins further back in the Proterozoic. Not everyone accepts this. Why is there no fossil record, except sponge biomarkers, before 600 Ma?

Triploblasts

Diploblasts

600 Ma

SnowballEarth

Page 55: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Triploblasts

Diploblasts

600 Ma

SnowballEarth

“Cambrian Explosion” as seen in the fossil record

A “slow fuse” is suggested by molecular clock analysis extending many lineages into the Cryogenian.

Page 56: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Triploblasts

Diploblasts

600 Ma

600 Ma sponge from China, 2015.Preserved in phosphate, 1 mm in size.

Slow fuse evidence

Page 57: Fossil Invertebrates of the Phanerozoicpages.geo.wvu.edu/~kammer/g231/MetazoanRadiation.pdfBurgess Shale Fossils • Most are soft-bodied fossils, a very rare kind of fossilization.

Palaeontology, July 2014

Conularid, 634 Ma, China.Extinct class of Cnidaria

SnowballEarth

600 Ma

Slow fuse evidence