ON FOSSIL PRESERVATION AND THE STRATIGRAPHIC RANGES OF TAXA

The fossil record is incomplete in the sense that taxa for which there are no preserved finds are unrepresented. Because the probability tha t there is at least one preserved find is greater for long-lived taxa, failure to account for this effect will bias estimation of mean taxon omic duration. This paper describes maximum likelihood estimation of m ean taxonomic duration, fossil preservation rate, and completeness of the local fossil record under a model in which duration has an exponen tial distribution and the locations of preserved finds follow a Poisso n process. The estimates under this model have simple closed forms. It is also straightforward to construct confidence regions for the model parameters. The method is applied to data on 110 trilobite species fr om the Upper Cambrian-Lower Ordovician in Oklahoma.