The Dinosaurs! Dinosaurs were the dominant animals for over 160 million years, from the late Triassic period, about 230 million years ago (Ma), until the end of the Cretaceous period, about 65 Ma, when most of them became extinct in the Cretaceous–Tertiary extinction event. The fossil record indicates that birds evolved from theropod dinosaurs during the Jurassic period, and most paleontologists regard them as the only clade of dinosaurs to have survived until the present day. The Dinosaurs! Walking with dinosaurs!