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Science 6 February 2009:
Vol. 323. no. 5915, pp. 767 - 771
DOI: 10.1126/science.1164905
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Reports

Signature of the End-Cretaceous Mass Extinction in the Modern Biota

Andrew Z. Krug,1 David Jablonski,1 James W. Valentine2

The long-term effects of mass extinctions on spatial and evolutionary dynamics have been poorly studied. Here we show that the evolutionary consequences of the end-Cretaceous [Cretaceous/Paleogene (K/Pg)] mass extinction persist in present-day biogeography. The geologic ages of genera of living marine bivalves show a significant break from a smooth exponential distribution, corresponding to the K/Pg boundary. The break reflects a permanent increase in origination rates, intermediate between the Mesozoic rate and the post-extinction recovery pulse. This global rate shift is most clearly seen today in tropical bioprovinces and weakens toward the poles. Coupled with the modern geographic distributions of taxa originating before and after the K/Pg boundary, this spatial pattern indicates that tropical origination rates after the K/Pg event have left a permanent mark on the taxonomic and biogeographic structure of the modern biota, despite the complex Cenozoic history of marine environments.

1 Department of Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue Chicago, IL 60637, USA.
2 Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, Berkeley, CA 94720, USA.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)