EXTINCTION PROCESSES EXTINCTION PROCESSES v Rare species are at risk.
Lecture 11 - The K/P Extinction and Radiation of - Indiana University
Transcript of Lecture 11 - The K/P Extinction and Radiation of - Indiana University
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Artist conception of moon-size object crashing into Mercury-size planet. (NASA/JPL-Caltech )
Reading: Benton, Chapters 9 & 10
and the radiation of placental mammals
The Cretaceous-Paleogene Extinction
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(International Commission on Stratigraphy)
Late Cretaceous time scale
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
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The Cretaceous-Paleogene (K-P) extinctionExtinction of the last non-avian dinosaurs
Major turnover in calcareous nanoplankton, especially coccolithophores
Major extinctions in ostracodes, scleractinian corals, ammonites, gnathostomes, as well as major changes to plant communities
60% 57% 82% 53%
47%
Marine diversity
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Bolide impact theoryProposed by Luis Alvarez, Walter Alvarez, Frank Asara, and Helen Michels in 1980
Theory based on high concentration of iridium in several boundary sections
Later evidence included presence of shocked quartz, chromium concentrations, and the discovery of Chicxulub crater in Yucatan Peninsula
Proposed that asteroid was 10 km in diameter, releasing energy equal to 2 million times the most powerful nuclear bomb
Effects: dust cloud lasting several years (blocking photosynthesis), blocked insolation, caused firestorms, and greenhouse effect
Watler and Luis Alvarez
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Science, 2010., 328: 973-976
Multiple causesMany or most paleontologists argue that impact alone can explain only part of the extinction.
Impact had an effect and caused final extinction of some organisms, but:
1. many groups had a longer pattern of extinction
2. many groups that should have been affected if bolide was a devastating as purported were not
Causes: regression of shallow seas, vulcanism and atmospheric changes, correlated ecological changes in plant, animal, and marine communities
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(Horner et al., 2010. PLoS One, 6(2): e16574)
The Hell Creek Fm., Eastern MontanaOne of the few terrestrial sections in the world that cross the K-P boundary
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(Horner et al., 2010. PLoS One, 6(2): e16574)
Total dinosaur diversity from Hell Creek Formation
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(Horner et al., 2010. PLoS One, 6(2): e16574)
Dinosaur diversity in Hell Creek Fm.Declines from seven genera to three
The final three
End Maastrichtian: 3 generaLate Maastrichtian: 32 generaEarly Maastrichtian: 32 generaLate Campanian: 48 genera
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((c) Greg Wilson)
Diversity in the last 2 million years before KPOther taxa show little or no decline
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
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Comparative extinction of terrestrial vertebrates
Taxon Number Extinct Number Survivors Percent extinction
Non-avian dinosaurs
3 0 100%
Mammals 18 13 60%
Crocodilians 1 4 20%
Turtles 2 15 12%
Amphibians 0 8 0%
Archibald, 2011. Extinction and Radiation
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
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The CenozoicThe most recent 65 million years
Formerly divided into the Tertiary and Quaternary, now divided into Paleogene, Neogene, and Quaternary
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
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Eutherian Orders
Centenial Museum, University of Texas El Passo
Arch
onta
Fera
eUn
gula
ta
Lipo
thyp
hla
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Asher and Helgen, 2010. BMC Evolutionary Biology, 10: 102.
Radiation of Eutheria - placental mammals
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Wible et al., 2009. Bulletin of the American Museum of Natural History, 327: 1-123.
Tribosphenic dentition - ancestral condition for TheriaInterlocking teeth that combine shearing, grinding, and puncturing
Associated with insectivorous diet
In Eutheria, ancestral dental formula is: I3, C1, P4, M3
All teeth but molars have deciduous counterparts (milk teeth, or baby teeth). Molars are not replaced.
Other dentition types rapidly derived from these, including omnivorous and herbivorous types formed by addition of hypocone and loss of paraconid
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
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Alistair Evans, http://users.monash.edu.au/~arevans/3d.html
Occlusion in Tribosphenic TeethChalinolobus gouldii, Gould’s Wattled Bat
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Diversity of dentitions and diets
ShrewInsectivorous
FoxCarnivorous to omnivorous
ShrewInsectivorous
DeerHerbivorous Wood rat
Granivorous
Protocone
Metacone
Paracone
Hypocone
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
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Uhen, 2010, Origin of Whales
Evolution of whales (Cetacea)First whales: Early Eocene of Pakistan and India, PakicetusDerived from Artiodactyla (contains living camels, pigs, deer)Closest living relative: Hippo (clade Whippomorpha)
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Uhen, 2010
Phylogeny of whales
Pakicetus: 49 mya Ambulocetus
Rhodocetus
Basilosaurus: 39 mya
Dorudon
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Uhen, 2010. Origin of Whales
Cenozoic geography and whales
Remnants of the Tethys Sea
Pangea, 251 mya
Tethys Sea
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Scientific papers for further readingArchibald, J.D. and 27 others. 2010. Cretaceous extinctions: multiple causes. Science, 328: 973-976.
Asher, R. J., N. Bennett, and T. Lehmann. 2009. The new framework for understanding placental mammal evolution. BioEssays, 31: 853-864.
Horner, J. R., M. B. Goodwin, and N. Myhrvold. 2010. Dinosaur census reveals abundant Tyrannosaurus and rare ontogenetic states in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA. PLoS One, 6(2): e16574.
Uhen, M.D. 2010. The origin(s) of whales. Annual Review of Earth and Planetary Science, 38: 189-219.