The Cretaceous period was the final period of the Mesozoic era, spanning the time between about 144 million years ago (end of the Jurassic period) and 65 million years ago (beginning of the Cenozoic era). It was the last part of the Age of Dinosaurs, although it did see the appearance of new kinds of dinosaurs, including the ceratopsian and pachycepalosaurid groups. Also from the Cretaceous have been found the first fossils of many insect groups, modern mammal and bird groups, and the first flowering plants.
The breakup of the world-continent Pangea, which began during the Jurassic, continued into the Cretaceous. This led to increased regional differences in floras and faunas between the northern and southern continents.
The end of the Cretaceous brought the end of many previously successful and diverse groups of organisms, such as non-avian dinosaurs and ammonites. The mass extinction at the Cretaceous-Tertiary boundary cleared the way for those groups that had previously taken secondary roles to come to the forefront.