Mass extinction effect on mammals disputed

A new phylogenic tree suggests ancestors of present-day mammals diversified millions of years after dinosaurs were wiped out, contradicting a popular theory

Graciela Flores
Mar 27, 2007
New findings are contradicting a popular theory that the late Cretaceous mass extinction, which eliminated non-avian dinosaurs and most existing fauna 65 million years ago, helped trigger the rise of present-day mammals. Instead, in a report in Nature this week, researchers suggest that ancestors of modern mammals coexisted with dinosaurs, survived this mass extinction event, and only experienced major diversification millions of years after dinosaurs disappeared."We think that the death of the dinosaurs didn't really have a strong effect, either positive or negative, on the extant groups," including today's mammals, lead author Olaf Bininda-Emonds of the University of Jena in Germany told The Scientist.Bininda-Emonds and a multidisciplinary team of researchers assembled and analyzed a mammalian "supertree," a comprehensive phylogenetic tree that combines some 2,500 smaller trees, and brings together existing fossil record data and new molecular analyses. "The supertree shows two major diversification peaks: A quick burst of...

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