But if one looks instead at the rate at which species are dying off, the picture becomes bleaker. - Ordovician extinction -When: about 445 million years agoSpecies lost: 60-70%Likely cause: Short but intense ice ageMost life at this time was in the oceans. - Devonian extinction -When: about 375-360 million years agoSpecies lost: up to 75%Likely cause: oxygen depletion in the oceanAgain, ocean organisms were hardest hit. - Cretaceous extinction -When: about 66 million years agoSpecies lost: 75%Likely cause: asteroid strikeA space rock impact is suspect No. But most mammals, turtles, crocodiles and frogs survived, along with birds as well as most sea life, including sharks, starfish and sea urchins.

Source: Bangkok Post May 06, 2019 09:11 UTC