PALEONTOLOGY:
Mass Extinctions Face Downsizing, Extinction
Richard A. Kerr
A bunch of sea urchins turned up in the Cretaceous like a bad penny, millions of years after they were believed to have gone extinct. Their reappearance casts doubt on the existence of one long-presumed mass extinction and by implication the existence of several others. In a paper in the latest issue of Paleobiology, a group of British paleontologists argue that the reason so many species disappeared from the fossil record in the Cenomanian-Turonian mass extinction 94 million years ago is because the fossils dissolved during sea-level changes.