Dinosaurs lived on Earth for over 160 million years, from about 240 million years ago until their extinction around 66 million years ago, spanning the Mesozoic Era which includes the Triassic, Jurassic, and Cretaceous periods

. Regarding individual dinosaur lifespans, it varied by species:

• Smaller dinosaurs like ceratopsians took 6 to 13 years to reach adult size, with the largest individuals living around 18 to 20 years

• Giant sauropods grew to adult size by 20 to 30 years and could live up to 41 to 55 years

• Some large dinosaurs such as Brachiosaurus may have lived up to 100 years, while smaller species like Compsognathus lived around 10 years

Scientists estimate dinosaur lifespans by analyzing growth rings in fossilized bones, similar to counting tree rings

. In summary, while dinosaurs as a group existed for over 160 million years, individual dinosaurs typically lived from about 10 years (small species) to up to around 50-100 years (large species)