Tiny eggs may explain why ammonites vanished while nautiloids survived asteroid aftermath

Some of the most beautiful creatures to grace the ancient seas, the ammonites, disappeared in the end-Cretaceous mass extinction that finished off the dinosaurs 65.5 million years ago. "It's a tragic story, because this incredibly diverse group made it through multiple mass extinctions, including the most dramatic mass extinction event in history," the Permian-Triassic extinction, which killed off 96% of marine species about 252 million years ago, says Michael Schmutzer, an evolutionary biologist at the University of Oxford in England.