Fossiliferous Outcropping (image) University of Chicago Caption The fossil mollusks in this Maryland outcrop lived approximately 15 million years ago. UChicago paleontologists Andrew Z. Krug and David Jablonski analyzed the fossil record of mollusks for the last 200 million years, finding that mass extinctions don't just remove evolutionary lineages, they exert a long-term influence on evolutionary rates among the survivors. Credit Susan Kidwell Usage Restrictions News organizations may use this image in connection with reporters about the research of Andrew Krug and David Jablonski. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.