Mesozoic Era

Mesozoic Era, one of the major divisions of geologic time, following the Paleozoic Era and preceding the Cenozoic Era. The Mesozoic Era, which lasted from approximately 251 million to 65 million years ago, may be characterized as the Age of Reptiles because their greatest development occurred during this era. One large and diverse group of reptiles, the dinosaurs, evolved, spread across the Earth, and died out all within this era. The first birds and mammals and the first flowering plants also appeared at this time. One of the most important topographical changes of the era in North America was the uplifting and extensive erosion of the Appalachian Mountains. The Mesozoic Era is divided into three time periods: the Triassic, Jurassic, and Cretaceous. See Geology; Paleontology.