the.com/cretaceous period

means The geological period from about 145 to 66 million years ago, the last era of the dinosaurs, ending in the mass extinction that wiped most of them out.

from From Latin 'creta,' meaning chalk — the period is named for the thick chalk beds (like England's White Cliffs of Dover) laid down by tiny marine organisms whose skeletons piled up on ancient seafloors. A geologist coined the term in the early 1800s, studying rock layers in the Paris Basin, long before anyone connected the era to dinosaurs or their asteroid-driven exit.