Other Permian detectives suspect the killer oozed up from the sea. For years scientists have ... The crisis for marine animals would have started when toxic levels of CO2 entered the shallows.

The Permian Period ran from 299 million to 252 million years ago—the Guadalupian is a slice from the middle of it—and ended with a great cataclysm. In the sea and on land, most species then ...

Some have proposed that the disappearance of certain predators and competitors allowed some of the surviving creatures to thrive. And others have proposed that the climate changes associated with the ...