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Dinosaur richness effect on end-Cretaceous mass extinction

From: Ben Creisler

First, I hope everybody in the path of Sandy on the US East Coast
pulls through OK.

A new online paper:

Jonathan S. Mitchell, Peter D. Roopnarine, and Kenneth D. Angielczyk (2012)
Late Cretaceous restructuring of terrestrial communities facilitated
the end-Cretaceous mass extinction in North America.
Proceedings of the National Academy of Sciences (advance online publication)
doi: 10.1073/pnas.1202196109

The sudden environmental catastrophe in the wake of the end-Cretaceous
asteroid impact had drastic effects that rippled through animal
communities. To explore how these effects may have been exacerbated by
prior ecological changes, we used a food-web model to simulate the
effects of primary productivity disruptions, such as those predicted
to result from an asteroid impact, on ten Campanian and seven
Maastrichtian terrestrial localities in North America. Our analysis
documents that a shift in trophic structure between Campanian and
Maastrichtian communities in North America led Maastrichtian
communities to experience more secondary extinction at lower levels of
primary production shutdown and possess a lower collapse threshold
than Campanian communities. Of particular note is the fact that
changes in dinosaur richness had a negative impact on the robustness
of Maastrichtian ecosystems against environmental perturbations.
Therefore, earlier ecological restructuring may have exacerbated the
impact and severity of the end-Cretaceous extinction, at least in
North America.