Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya; their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and paraphyletic pseudo-extinct non-avian dinosaurs, which are all dinosaurs other than birds.
Dinosaurs once existed 230 to 66 million years ago, before going extinct from the Great Robloxian Asteroid that destroyed Earth long before the first Robloxians appeared. As a result, no Robloxian so far has encountered a real dinosaur or even a prehistoric animal that was made extinct by the asteroid, so the subject of Robloxians encountering dinosaurs and prehistoric animals has been featured prominently in science fiction movies.
An Bloxargentinosaurus wandering while a T Rex passes by in the Late Cretaceous Period.