Abstract

The pattern of variation in taxonomic turnover on short timescales is expected to leave detectable signals even when taxonomic data are compiled at coarser timescales. Global, stage-level data on first and last appearances of marine animal genera are analyzed to determine whether it is more likely that origination and extinction were spread throughout stages or that they were concentrated at a single episode per stage. The analysis takes incomplete and variable sampling of stratigraphic ranges into consideration, and it takes advantage of the fact that empirical sampling rates are within the range of values that allow the within-stage turnover models to be distinguished on the basis of stage-level data. The data strongly support the model of a single extinction pulse per stage over the alternative of continuous extinction within the stage. Pulsed origination is also supported over continuous origination, but the case is not as compelling as for extinction. Differential support for pulsed turnover is not confined to a few stages. Pulsed turnover therefore appears to be a general feature of the evolution of marine animals.

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