What are Some Cretaceous Organisms?
The Cretaceous Period is a geologic period that stretches from 145.5 to 65.5 million years ago. With a total duration of 80 million years, the Cretaceous is the longest geologic period in the last 542 million years. It is famous for being dominated by dinosaurs and other large reptiles, such as pterosaurs (winged reptiles), mosasaurs, plesiosaurs, ichthyosaurs, and pliosaurs (all marine reptiles). Mammals were present, as tiny scavengers in the night, as well as some giant amphibians that survived through geographic isolation. Birds began to diversify and compete with pterosaurs for the skies. During the Cretaceous, the climate was warm and sea levels were high. Much of this warmth came from abundant volcanic activity that released large amounts of the greenhouse gas carbon dioxide into the atmosphere. Forests, made of conifers and/or cycads, covered the planet, including the South Pole. Much of North America was flooded by an epicontinental sea called the Western Interior Seaway, and
