Previous estimates of the global generic diversity loss for echinoids at the Cretaceous/Tertiary boundary have been as high as 65%. However, these estimates are based on compilations of occurrence data from the existing literature and are plagued by problems of inconsistent taxonomic usage. Analysis of a taxonomically standardized, phylogenetically framed data set demonstrates that the generic extinction rate for heart urchins was 33%, and that the two constituent orders suffered markedly different fates. Whereas holasteroids lost 56% of their generic diversity at the end of the Cretaceous, only 17% of spatangoid genera became extinct. Correlation of extinction with a range of geographical, environmental, and biological factors has been explored. Survivorship is significantly correlated only with feeding strategy, implying that the extinctions of atelostomate echinoids at the Cretaceous/Tertiary boundary were nutrient driven. In addition, feeding strategy is correlated with atelostomate clade affinity, explaining the differential fates of holasteroids and spatangoids at the end of the Cretaceous.

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