Also found in: Dictionary
Related to Cretaceous period: Tertiary period
, Triassic period
, Paleogene Period
Cretaceous period the geological period which began about 135 million years BP and ended 65 million years BP. It is usually divided into Lower (135–95 million years) and Upper (94–65 million years) periods. The dominance of flowering plants began during this period and large reptiles (e.g. dinosaurs) and ammonites were extinct by its end. By the end of the period, the Thames was at 40 °N and Britain was still moving northwards. See GEOLOGICAL TIME.