Dinosaurs are a diverse group of animals of the clade Dinosauria. They first appeared during the Triassic period, 231.4 million years ago, and were the dominant terrestrial vertebrates for 135 million years, from the beginning of the Jurassic (about 201 million years ago) until the end of the Cretaceous (66 million years ago), when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups (and some three-quarters of plant and animal species on Earth) at the close of the Mesozoic Era. The fossil record indicates that birds evolved from theropod dinosaurs during the Jurassic Period and, consequently, they are considered a subgroup of dinosaurs. Some birds survived the extinction event that occurred 65 million years ago, and their descendants continue the dinosaur lineage to the present day.
Uploaded: Jul 15, 2015