title: Periodic extinction of families and genera.
abstract: Eight major episodes of biological extinction of marine families over the past 250 million years stand significantly above local background (P < 0.05).  These events are more pronounced when analyzed at the level of genus, and generic data exhibit additional apparent extinction events in the Aptian (Cretaceous) and Pliocene (Tertiary) Stages. Time-series analysis of these records strongly suggests a 26-million-year periodicity.  This conclusion is robust even when adjusted for simultaneous testing of many trial periods.  When the time series is limited to the four best-dated events (Cenomanian, Maestrichtian, upper Eocene, and middle Miocene), the hypothesis of randomness is also rejected for the 26-million-year period (P < 0.0002).
authors.affiliation: Department of Geophysical Sciences, University of Chicago, IL 60637, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Raup
authors.forename: J J
authors.initials: JJ
authors.lastname: Sepkoski
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005580:Fossils; D055593:Geological Phenomena; D005844:Geology; D008386:Marine Biology; D010163:Paleontology / Q000706:statistics & numerical data*; D010507:Periodicity