Artwork of a Hybodus shark, a predator that evolved in the late Permian and survived the mass extinction CHRISTIAN DARKIN/SCIENCE PHOTO LIBRARY The worst known mass extinction wiped out over 80 per cent of marine species. But despite these huge losses, many ecosystems did not collapse, with a variety of animals and even top predators managing to survive the cataclysm. The findings suggest that each ecosystem’s fate was determined, in part, by its own unique mix of species. The same may be true of modern marine ecosystems, which are also facing major threats from climate change. The end-Permian extinction struck about 252 million years ago. It seems to have been caused by massive volcanic eruptions in what is now Siberia, which led to drastic global warming, low oxygen levels in the oceans and a host of other threats. Some animal groups, such as trilobites and eurypterids (sea scorpions) were entirely wiped out; others suffered huge losses. In the aftermath, many new groups arose, including dinosaurs and ichthyosaurs. Given that so many species died out, researchers …