Cretaceous Period

Cretaceous Period (₁₄₅–66 million years ago)

The Cretaceous Period is the final period of the Mesozoic Era, ending with the mass extinction that wiped out all non‑avian dinosaurs.

World & Climate

• Continents continue to drift toward their modern positions.
• Sea levels are high; large shallow seas cover parts of continents.
• Climate is generally warm, though there is more variation than in the Jurassic.

Dinosaurs in the Cretaceous

This period shows the greatest diversity of dinosaurs.

Examples of famous Cretaceous dinosaurs:

• Theropods – Tyrannosaurus rex, Velociraptor, Spinosaurus.
• Ceratopsians – horned dinosaurs like Triceratops.
• Hadrosaurs – duck‑billed dinosaurs such as Edmontosaurus, often in large herds.
• Ankylosaurs – heavily armored dinosaurs with clubbed tails.
• Titanosaur sauropods – very large long‑necked herbivores in many regions.

Birds and Other Life

• Birds (avian dinosaurs) diversify and begin to occupy many ecological niches.
• Flowering plants (angiosperms) appear and spread, changing ecosystems and herbivore diets.
• Marine life includes mosasaurs, plesiosaurs, and diverse fish and invertebrates.

End‑Cretaceous Mass Extinction

Around 66 million years ago, a major extinction event (linked to a large asteroid impact and other environmental stresses) causes the extinction of all non‑avian dinosaurs, many marine reptiles, ammonites, and more.

Only birds (avian dinosaurs) and certain other groups survive into the Cenozoic Era.