Cretaceous

The final period of the Mesozoic Era, lasting from about 145 to 66 million years ago. It ended with a mass extinction that eliminated non-avian dinosaurs.

Cretaceous–Paleogene extinction event: A mass extinction about 66 million years ago that eliminated non-avian dinosaurs and many other groups. This event marks the Cretaceous's abrupt end.
Tyrannosaurus: A genus of large, carnivorous theropod dinosaurs from Late Cretaceous North America. Tyrannosaurus exemplifies the giant predators of the period's final ecosystems.
Geologic time scale: A chronological framework that divides Earth's history into eons, eras, periods, epochs, and ages. It locates the Cretaceous within Earth's broader chronology.
International Commission on Stratigraphy: The international body that standardizes geological time units and their boundaries. Its chart gives the Cretaceous its formal position and dates.
K–Pg extinction survivors: Organisms and lineages that persisted through the mass extinction at the end of the Cretaceous. Their survival shaped which ecosystems could recover after the period ended.
Chicxulub crater: A large impact structure in Mexico's Yucatán Peninsula, formed by an asteroid impact about 66 million years ago. The crater records the impact linked to the period's terminal extinction.
Triceratops: A genus of horned, herbivorous dinosaurs from Late Cretaceous North America. Its fossils capture the distinctive dinosaur communities of the final Cretaceous.
Mesozoic: The geologic era between the Paleozoic and Cenozoic, spanning about 252 to 66 million years ago. The Cretaceous is the Mesozoic's final period.
Radiometric dating: A method for determining ages from the decay of radioactive isotopes in minerals or other materials. It helps establish absolute ages for Cretaceous rocks and boundaries.
Mammalia: The vertebrate class whose living members produce milk and typically have hair. Mammalian lineages survived the end-Cretaceous extinction and later diversified.

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