This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The Signor-Lipps effect holds that a truly sudden (simultaneous) extinction of a group of taxa may appear gradual in the fossil record due to incomplete fossil preservation. Therefore, much work in the last two decades has been devoted to devising statistical tests for a simultaneous extinction of all taxa in a stratigraphic section. Rather than being limited to rejecting or failing to reject this single scenario, however, the PI will develop methods to estimate the range of extinction scenarios that is consistent with the fossil record. In other words, rather than testing the oversimplified distinction of simultaneous or gradual, the PI will ask the question how gradual? The PI will develop a mathematical confidence interval for the duration of a mass extinction, either in terms of the time or stratigraphic thickness between the first and last taxon to go extinct. The project proposes to implement a statistical test that will provide 95% confidence that the extinction took place over a duration of 12 to 18 meters of stratigraphic thickness. This does not deny the possibility of a truly simultaneous extinction; rather, within this framework, a simultaneous extinction is one in which the confidence interval contains a possible duration of zero meters. The proposed project is broadly interdisciplinary and will specifically apply this mathematical model to estimate the duration of the end-Permian mass extinction, arguably the most severe biotic crisis of the Phanerozoic.
