Effects of sampling standardization on estimates of Phanerozoic marine diversification

Global diversity curves reflect more than just the number of taxa that have existed through time: they also mirror variation in the nature of the foss il record and the way the record is reported. These sampling effects are be st quantified by assembling and analyzing large numbers of locality-specifi c biotic inventories. Here, we introduce a new database of this kind for th e Phanerozoic fossil record of marine invertebrates. We apply four substant ially distinct analytical methods that estimate taxonomic diversity by quan tifying and correcting for variation through time in the number and nature of inventories. Variation introduced by the use of two dramatically differe nt counting protocols also is explored. We present sampling-standardized di versity estimates for two long intervals that sum to 300 Myr (Middle Ordovi cian-Carboniferous; Late Jurassic-Paleogene), Our new curves differ conside rably from traditional, synoptic curves. For example, some of them imply un expectedly low late Cretaceous and early Tertiary diversity levels. However , such factors as the current emphasis in the database on North America and Europe still obscure our view of the global history of marine biodiversity . These limitations will be addressed as the database and methods are refin ed.