Cretaceous–Tertiary extinction event
The Cretaceous–Tertiary extinction event (shorthand KT-Exintion Event) was a global catastrophe that occurred 65.5 million years ago. This event marks the sudden extinction of most species of dinosaur. Scientists generally believe the cause was an asteroid impact.
In verses debate
The KT-Extinction event is sometimes used as a watermark in terms of damage inflicted.