Lecture 11 - The K/P Extinction and Radiation of - Indiana University

Department of Geological Sciences | Indiana University (c) 2011, P. David Polly

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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


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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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Total dinosaur diversity from Hell Creek Formation


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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


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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


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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


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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


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Alistair Evans, http://users.monash.edu.au/~arevans/3d.html

Occlusion in Tribosphenic TeethChalinolobus gouldii, Gould’s Wattled Bat

http://users.monash.edu.au/~arevans/3d.html

http://users.monash.edu.au/~arevans/3d.html


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Diversity of dentitions and diets

ShrewInsectivorous

FoxCarnivorous to omnivorous

ShrewInsectivorous

DeerHerbivorous Wood rat

Granivorous

Protocone

Metacone

Paracone

Hypocone


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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.

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Lecture 11 - The K/P Extinction and Radiation of - Indiana University