Geological Periods
The Cretaceous period is the last of the three parts into which the Mesozoic era is divided. It covers from the end of the Jurassic period (145.5 ± 4.0 million years ago) to the beginning of the Paleocene (65.5 ± 0.3 million years ago).
The Jurassic period is one of the three parts into which the Mesozoic era is divided. It spans from the end of the Triassic period (199.6 ± 0.6 million years ago) to the beginning of the Cretaceous period (145.5 ± 4.0 million years ago).
The Triassic is the first of the three parts into which the Mesozoic era is divided. It covers from the end of the Permian (251 ± 0.4 million years ago) to the beginning of the Jurassic (199.6 ± 0.6 million years ago).