Extinction rates higher in open-ocean settings during mass wipeouts
Washington | November 21, 2009 4:17:55 PM IST
 

In a new research, a team of paleontologists has found that extinction rates higher in open-ocean settings during mass extinctions.

The research was conducted by Arnie Miller, University of Cincinnati professor of paleontology in the McMicken College of Arts and Sciences, and co-author Michael Foote of the University of Chicago.

For many years, paleobiological researchers interested in the history of biodiversity have focused on charting the many ups (evolutionary radiations) and downs (mass extinctions) that punctuate the history of life.

Because the preserved record of marine animals is unusually extensive in comparison, say, to that of terrestrial animals such as dinosaurs, it's been easier to accurately calibrate the diversity and extinction records of marine organisms.

"Paleontologists now recognize that there were five particularly large, worldwide mass extinction events during the history of life, known among the cognoscenti as 'The Big Five'," said Miller.

In their research, Miller and Foote assembled data on the occurrences of marine genera from the Paleobiology Database for the Permian through Cretaceous periods, during which both major settings are well preserved in the fossil record.

From that, they determined whether these occurrences were from epicontinental seas or open-ocean-facing settings, and they then compared extinction and origination rates in the two settings throughout the interval.

"This was a particularly juicy interval to work with, because it includes three of The Big Five, including the Late Permian mass extinction, the largest extinction in the history of marine animal life, and the end-Cretaceous event, which also did in the dinosaurs and has been associated previously with the impact of a big comet or asteroid," Miller said.

Miller and Foote found that, while extinction rates in the two settings did not generally differ from one another during "background" times between mass extinctions, there was a strikingly different pattern for the mass extinctions.

Extinctions rates during mass extinctions were significantly higher in open-ocean-facing settings than in epicontinental seas, indicating that open-ocean settings were more susceptible to the mass-extinction-causing agents.

Miller and Foote's finding bolsters the view that a drop in sea level was uniquely important as a cause of extinction in that interval.

Although their results to date are compelling, Miller and Foote are not done.

Among other things, they intend to extend their analyses back through the entire Paleozoic Era, when epicontinental seas were at their zenith. (ANI)

 

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