The Mesozoic includes three Geologic Periods; from oldest to youngest, the Triassic, Jurassic and Cretaceous. It extended from roughly 245 million years before present to roughly 64 million years.
It followed the Paleozoic Era and preceded the Cenozoic Era.
The Mesozoic is known as the Age of Dinosaurs. It also saw the development of early birds and mammals, and of flowering plants (angiosperms). At the end of the Mesozoic, all the major body plans of modern life were in place although in some cases—notably the mammals—the forms that existed at the end of the Cretaceous were relatively primitive.