225 million years ago, in the transition from the Permian period to the Triassic, 90-95% of all marine species died out.
195 million years ago, in the transition from the Triassic period to the Jurassic, there was another extinction event.
65 million years ago, the Cretaceous-Tertiary extinction event killed about 50% of all species died out, including the dinosaurs.
Some people claim that we are living in the middle of another, man-made extinction event right now.
See also