The second of the Earth's three major geologic eras of Phanerozoic time and the interval during which the continental landmasses as known today were separated from the supercontinents Laurasia (North America and Eurasia) and Gondwana by continental drift. It occurred before the Cenozoic and after the Palaeozoic and was marked by the development of the ancestors of the major plant and animal groups that exist today and the extinction of the dinosaur, suddenly at the end of the Cretaceous Period. It lasted from about 245 to 66.4 million years ago and included, in order, the Triassic Period, the Jurassic Period, and the Cretaceous Period.