Mesozoic the Phanerozoic Eon, preceded by the Paleozoic ("ancient life") and succeeded by the Cenozoic ("new life"). The era is subdivided into three major periods: the Triassic, Jurassic, and Cretaceous, which are further subdivided into a number of epochs and stages. The era began in the wake of the Permian–Triassic extinction event, the largest well-documented mass extinction in Earth's history, and ended with the Cretaceous–Paleogene extinction event, another mass extinction whose victims included the non-avian dinosaurs. The Mesozoic was a time of significant tectonic, climate and evolutionary activity. The era witnessed the gradual rifting of the supercontinent Pangaea into separate landmasses
Wasson Bluff dinosaur tracks, at his Parrsboro Rock and Mineral Shop and Museum. One of them, also found at Wasson Bluff, is a track that may have been made by a primitive, two-legged, crocodile-like creature that was nearly long. In January 1986, American paleontologists Paul Olsen and Neil Shubin announced they had recovered hundreds of thousands of bones at Wasson Bluff, the largest fossil find in North America dating from the geological period 200 million years ago known as the Triassic-Jurassic boundary. It was a time when massive lakes of lava spewed from fissures in the earth as the supercontinent Pangea broke