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Anther occurred when the Cretaceous period became the Tertiary about 65 million years ago, when 75 percent of species disappeared. This article is about the first mass extinction at the end of the Ordovician geological period 440 million years ago, when about 86 percent of species were killed.
Mass extinction âchanges the rules of evolution.â. Images: 1) A fossil skull of Dunkleosteus, an apex predator fish that lived between 380 million and 360 million years ago, and had what is believed to be historyâs most powerful bite./Michael LaBarbera, courtesy of The Field Museum.