They range from 450 million years ago to the last, the K-T, number four, but the biggest of all was the P, or the Permian extinction, sometimes called the mother of all mass extinctions.
从4.5亿年前， 到上一次白垩纪第三纪灭绝，也就是第四次， 但规模最大的一次是二叠纪生物绝灭事件， 有时候也被叫作“大规模灭绝之母”。