The right answer is Cretaceous
The Cretaceous corresponds to the last period of the Mesozoic (or secondary era). It ranges from -145.5 million years to -65.5 million years.
In the Cretaceous, the global climate was particularly hot, which allowed the massive development of plankton (chalk banks), but also that of large aquatic and terrestrial reptiles.
The end of the Cretaceous was marked by the biological crisis that saw the disappearance of the dinosaurs, but also 76% of the marine species of the planet.