A dinosaur is a type of reptile that lived during the Mesozoic area (240 to 65 million years ago). Dinosaurs appeared during the Triassic and flourished during the Jurassic and Cretaceous periods, after which they disappeared under contested circumstances. Perhaps a meteorite crashed down in Chixculub, in Central America, 65 million years ago.
Dinosaurs dominated the Earth's ecosystems throughout the Secondary Era. They ranged in size from 40 cm (Microraptor Gui) to 35 m (Futalongkosaurus).
There were 2 major types of dinosaurs: the Saurischians and Ornithischians. The Saurischians included Sauropods (herbivores, the largest dinosaurs, including Diplodocus) and Theropods (carnivores, for example: Tyrannosaurus). There was a wide variety of Ornithischian species, and all were herbivores (e.g.: Stegosaurus, Ankylosaurus, Triceratops).
A group of Theropods (Dromaeosaurids) is classically considered to be the group birds come from.