Cretaceous

Cretaceous is from the Latin "creta" = chalk. This is the last period of the Secondary era from 137 to 65 million years ago, during the course of which the planet's particularly warm climate enabled the massive development of plankton (forming chalk beds) and of the great aquatic and terrestrial reptiles. This period is often divided into Early Cretaceous and Late Cretaceous, the limit being between the Albian and Cenomanian epochs.