Dinosaur

Dinosaurs are prehistoric reptiles that have lived on Earth from about 228 million years ago to the present. Modern birds are one kind of dinosaur because they share a common ancestor with non-avian dinosaurs. Non-avian dinosaurs (all dinosaurs besides birds), which are now extinct, varied greatly in shape and size.

These ancient reptiles lived on land, laid eggs, and built nests. They walked on their toes, standing upright on pillarlike legs and holding their long, bony tails off the ground. Although most dinosaurs are now extinct, one group of dinosaurs still roams the planet today birds.