Five past extinctions: Some event near end of the Ordovician period, 440m years ago, wiped out almost all corals and fish, and 25 % of all families of creatures.

• 历史上曾发生过的5次物种大灭绝：4．4亿年前奥陶纪将要结束时的一些事件使几乎所有的珊瑚和鱼类以及25%25的物种灭绝；