According to evolutionary dogma, dinosaurs first appeared during the Triassic period, 231.4 million years ago, and were the dominant terrestrial vertebrates for 135 million years, from the start of the Jurassic (about 200 million years ago) until the end of the Cretaceous (66 million years ago). It was then that the alleged Cretaceous-Tertiary extinction event or the K-T event (the name given to the die-off of the dinosaurs and other various lifeforms) took place some 65.5 million years ago.