Dinosaurs lived throughout the Mesozoic Era, which began 245 million years ago and lasted for 180 million years. It is sometimes called the Age of the Reptiles. The era is divided into three periods TRIASSIC 245 to 208 million years ago During the Triassic period, all land on Earth existed as one enormous mass. It was called Pangaea. The supercontinent slowly began to break up during the Triassic Period. Some reptiles, frogs, turtles and crocodiles existed earlier, but dinosaurs didn’t appear until late in the Triassic period. The period marked the rise of small, lightly built dinosaurs. The first mammals evolved during the Triassic period. Most of the plants that existed were evergreens. The period ended with a mass extinction that wiped out most animals and reptiles. An entire order of plants or animals dies out in a mass extinction. The dinosaurs that survived flourished in the next period, the Jurassic. JURASSIC 208 to 146 million years ago The supercontinent continued to break apart Dinosaurs ruled the land and flourished during the period Herbivores and carnivores increased in size; some of the largest dinosaurs emerged during the Jurassic period Birdlike dinosaurs first appeared Flowering plants began to appear late in the period The Jurassic period also ended with an extinction, but it was not as extensive as the one in the Triassic period. Only a few types of dinosaurs died out. CRETACEOUS 146 to 65 million years ago Pangaea continued to separate into smaller continents A wide variety of dinosaurs roamed the land Birds flourished and spread all over the globe Flowering plants developed Mammals flourished Dinosaurs became extinct by the end of the period. The extinction, the second largest of all time, marked the end of the Age of Reptiles and the beginning of the Age of Mammals.