Practice question

Extinction of Trilobita finally occurred during end-Permian mass extinction about 252 million years ago, the most severe Phanerozoic crisis linked to Siberian Traps flood basalt volcanism, global warming, ocean anoxia, hypercapnia and acidification eliminating roughly 96 percent marine species. Trilobites already in decline after Late Devonian extinctions could not recover, disappearing with reef builders and many brachiopods. Triassic extinction affected crurotarsal archosaurs, Cretaceous extinction eliminated non-avian dinosaurs at 66 million years, Ordovician extinction reduced many marine taxa but trilobites survived, making Permian boundary terminal for the group.