Mass extinctions alter extinction and origination dynamics with respect to body size

Whether mass extinctions and their associated recoveries represent an intensification of background extinction and origination dynamics versus a separate macroevolutionary regime remains a central debate in evolutionary biology. Previous focus has been on extinction, but origination dynamics may be equally or more important for long-term evolutionary outcomes. The evolution of animal body size is an ideal process to test for differences in macroevolutionary regimes, as body size is easily determined, comparable across distantly related taxa, and scales with organismal traits. Here, we test for shifts in selectivity between background intervals and the “Big Five” mass extinction events using capture-mark-recapture models. Our body-size data cover 10,203 fossil marine animal genera spanning 10 Linnaean classes with occurrences ranging from Early Ordovician to Late Pleistocene (485–1 Mya). Most classes exhibit differences in both origination and extinction selectivity between background in...