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After the Cretaceous–Paleogene extinction that killed off most of the dinosaurs, for example, the top carnivores for a while were not the mammals that ultimately replaced them but giant, flightless birds known as "terror birds."

The average predicted extinction rate for freshwater animals and plants today is three orders of magnitude higher than it was during the Cretaceous–Paleogene extinction event 66 million years ago, when an asteroid likely killed the dinosaurs.

Similarly, a 2021 study in the journal Communications Earth & Environment found that past extinction rates for freshwater animals and plants today is three orders of magnitude higher than it was during the Cretaceous–Paleogene extinction event which killed all of the dinosaurs 65 million years ago.

A 2021 study in the journal Communications Earth & Environment found that the average predicted extinction rate for freshwater animals and plants today is three orders of magnitude higher than it was 66 million years ago during the Cretaceous–Paleogene extinction event.

Similarly, a 2021 study in the journal Communications Earth & Environment reported that the average predicted extinction rate for freshwater animals and plants today is three orders of magnitude higher than it was 66 million years ago, when the dinosaurs famously went extinct during the so-called Cretaceous–Paleogene extinction event.