Cohort analysis of generic survivorship

Abstract

Cohort analysis provides an effective method of analysing taxonomic survivorship in the fossil record where large data sets are available. An analysis of the stratigraphic ranges of about 8,500 fossil genera and subgenera shows that survivorship patterns are substantially the same throughout the Phanerozoic. These patterns are used to calculate an average value for mean species duration among fossil invertebrates (11.1 Myr.). Also, the extra extinctions near the Permo-Triassic boundary are shown to be equivalent to about 85 Myr of normal, background extinction.