The Ordivician-Silurian extinction event occurred around 450 to 440 million years ago.  During this mass extinction 27% of families and 57% of all genera went extinct.  One theory as to why this extinction happened is that the continent called Gondwanaland that included Antarctica, South America, Africa, India and Australia moved close to the south pole …

Continue reading First Mass Extinction:  Ordivician-Silurian Extinction Event