Cretaceous-Tertiary Mass Extinction Event
This was the famous event responsible for wiping out The Dinosaurs. After the meteor impact, a dark period of about 1-10 years followed, as the sunlight was virtually blocked out. With little sunlight available, the symbiotic zooxanthellae algae within the coral began to starve and coral again became extinct. They made another shortlived comeback 55million years ago, before sufering extinction again, this time due to The Paleocene-Eocene Thermal Maximum.2
65 Million Years Ago