Textbook Problem

The diversity or modem vertebrates was shaped in part by mass extinctions. The most severe extinction event we know of occured at the border between the Permian and Triassic periods about 250 million years ago. An estimated 96 percent of the marine species and 70 percent or land species disappeared in what is sometimes called "The Great Dying." The cause of this mass extinction remains under investigation. Suggested causes include an asteroid impact, extreme volcanic activity, or a sudden release of carbon dioxide from deposits on the sea floor. Which groups of vertebrates were present when this mass extinction event occurred? Which evolved afterward?