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The Decline and Fall of the Non-avian Dinosaurs MacLeod, N., Palaeontology Department, Natural History Museum, Cromwell Road, London,
 

Summary: The Decline and Fall of the Non-avian Dinosaurs
MacLeod, N., Palaeontology Department, Natural History Museum, Cromwell Road, London,
SW7 5BD, UK; Archibald, J. D., Department of Biology, San Diego State University, San Diego,
CA 92182-4614, USA
Despite claims to the contrary, the cause or causes of the non-avian dinosaur extinction at the
end of the Cretaceous remain as controversial as ever. The reason little progress has been, and
perhaps will never be made, has to do with (1) the nature of the end-Cretaceous dinosaur record
and (2) the nature of cause-effect tests involving historical data. Two recent proposals have
appeared recently that purport to account for this extinction. Both assume a bolide impact was the
sole cause. The first suggests that following collision, impact ejecta re-entering the atmosphere
would create a `thermal pulse' that would kill any land-dwelling organism that could not find
shelter quickly. While this scenario may account for the general pattern of dinosaur extinction, it
falters when its predictions are referenced to other terrestrial (e.g., birds, evidence for wildfires,
evidence from terrestrial invertebrates) and marine groups. The second proposal addresses the
data used to support the long-standing observation that non-avian dinosaur species richness
values declined from a Late Campanian high through the Maastrichtian. This proposal uses a
questionable interpretation of rarefaction results to suggest that Late Maastrichtian values were
the equal of--if not greater than--Late Campanian values. A reanalysis of the data on which
these conclusions are based not only fails to reproduce these results, it confirms the magnitude of
the Maastrichtian dinosaur richness decline and offers further detail into that decline's taxonomic

  

Source: Archibald, J. David - Department of Biology, San Diego State University

 

Collections: Biology and Medicine; Geosciences