Extinction and quiescence in marine animal genera

If last appearances of marine animal genera are taken as reasonable proxies for true extinctions, then there is appreciable global extinction in every stage of the Phanerozoic. If, instead, backsmearing of extinctions by incomplete sampling is explicitly taken into consideration, a different view of extinction emerges, in which the pattern of extinction is much more volatile and in which quiescent time spans-with little or no global extinction for several million years-are punctuated by major extinction events that are even more extreme than is generally thought. Independent support for this alternative view comes from analysis of genus occurrence data in the Paleobiology Database, which agrees with previous estimates of sampling probability and implies that offsets between extinction and last appearance of one or more stages are quite probable.