Selectivity of extinction among sea urchins at the end of the Cretaceous period

By compiling large databases and searching for environmental and palaeobiological correlates associated with survival, insight can be gained into the driving mechanisms involved in mass extinctions(1-4). Although this approach lacks precise temporal resolution and thus cannot be used to investigate how rapidly extinction took place, it provides a broad overview, less plagued by sampling problems caused by shifting facies. Here we present a global analysis of a major marine invertebrate group, the sea urchins, which suffered 36% extinction at genus level in the late Maastrichtian age and continuing high levels of extinction in the Danian age. No preferential survivorship was found for clades with widespread distribution, but there was a strong correlation between feeding strategy and survivorship at the end of the Cretaceous period. Surprisingly, however, clades whose larvae must feed to reach metamorphosis were not significantly harder hit than those with non-feeding larval development. Our results indicate that nutrient supply was a crucial factor in driving K/T-boundary extinctions, with selection more strongly focused on benthic adult than on larval planktotrophic stages.