Paleontologists Find Extinction Rates Higher in Open-Ocean Settings During Mass Extinctions>>>

ScienceDaily (Nov. 20, 2009) — 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 (sea-dwelling) 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,'" says Miller. "Much ink in research journals has been spilled over the past few decades on papers investigating the causes of these events."

Although researchers have long understood the potential value of "dissecting" mass extinctions, to ask whether some environments and organisms were affected more dramatically than others, little attention has been paid to a major dichotomy observed among marine sedimentary rocks and fossils: the distinction between epicontinental seas, which were broad shallow seas (typically less than 100 meters in depth) that once covered large regions of present-day continents, and open-ocean-facing coastlines, such as the continental shelves that rim many continents.

Today, it is difficult to appreciate that there was a time when regions such as Cincinnati were once covered by epicontinental seas, which gradually diminished over time so that almost none are left in the present day. And yet, a large percentage of Earth's fossil record is associated with these settings in the geological past, and there are many reasons to believe that their environmental properties were very different from open-ocean settings. See More>>>