(initial capital letter) Geology. noting or pertaining to a period of the Mesozoic Era, from 140 million to 65 million years ago, characterized by the greatest development and subsequent extinction of dinosaurs and the advent of flowering plants and modern insects.
–noun
3.
(initial capital letter) Geology. the Cretaceous Period or System.
Origin: 1665–70; < L crētāceus, equiv. to crēt(a) chalk, clay (cf. crayon) + -āceus-aceous; the geological period was defined from the chalk beds of SE England and associated formations
Cretaceous (krĭ-tā'shəs) Pronunciation Key
The third and last period of the Mesozoic Era, from about 144 to 65 million years ago. During this time the supercontinent Pangaea continued to split up, with modern-day South America and Africa splitting apart, the Atlantic Ocean widening, and India disconnecting itself entirely from the other landmasses to which it was attached. Dinosaurs continued to be the dominant terrestrial animals, but many insect groups, modern mammals and birds, and the angiosperms (flowering plants) also first appeared. The Cretaceous Period ended with a mass extinction event in which about 75 percent of all species, including marine, freshwater, and terrestrial organisms, became extinct. See Chart at geologic time.
[kri-tey-shuh
s] 