What caused the End Ordovician extinction? When did it start and which animals were affected? The End Ordovician extinction was the first of the Big Five mass extinction events in the history of the Earth. The term actually refers to two extinction periods, which together wiped out 86% of the marine species. Scientists attribute it to a sudden cooling of the climate that began around 444 million years ago. Read about the causes and effects of the End Ordovician extinction.
End Ordovician Extinction: The First and the Deadliest
