The Cretaceous Period was the period between 145.5 and 65.5 million years ago, the last period of the Mesozoic Era, following the Jurassic and ending with the extinction of the dinosaurs.
The Jurassic Period was the second segment of the Mesozoic Era. It occurred from 199.6 to 145.5 million years ago, following the Triassic Period and preceding the Cretaceous Period.