The Triassic Period, from 245 to 208 million years ago, and the Jurassic Period, from 208 to 144 million years ago, are the middle and lower subdivisions of the
Mesozoic Era. The Triassic saw the rise of the dinosaurs. During the Jurassic, dinosaurs continued to rule, and the first birds began to evolve.
Triassic and Jurassic features of the United States: