A global catastrophe 66 million years ago led to the extinction of all non-avian dinosaurs, and large marine reptiles like mosasaurs and plesiosaurs. But what happened to the sharks? According to a study of sharks' teeth publishing August 10th in the open-access journal PLOS Biology by Mohamad Bazzi of Uppsala University and colleagues, shark-tooth diversity remained relatively constant across the mass extinction event at the end of the Cretaceous.