When did dinosaurs live? Dates for the whole Mesozoic era
Dinosaurs lived from 240 to 66 million years ago across the Triassic, Jurassic and Cretaceous periods.
The three periods of the dinosaur age
Dinosaurs appeared about 240 million years ago in the Triassic period and disappeared 66 million years ago at the end of the Cretaceous. Scientists divide their reign into three periods: Triassic (252–201 million years ago), Jurassic (201–145) and Cretaceous (145–66). Together these form the Mesozoic era, the age of reptiles.
People often imagine all dinosaurs living together, but Stegosaurus and Tyrannosaurus are separated by more time than Tyrannosaurus and humans. Early dinosaurs were small, dog-sized runners, and only later did giants like Brachiosaurus and apex predators like Allosaurus evolve.
How the age ended
About 66 million years ago a 10-kilometer asteroid hit near modern Mexico, throwing dust that blocked sunlight for years. Without light, plants died, then plant-eaters, then predators — about 75 percent of all species vanished, including every land animal heavier than 25 kilograms.
Only small feathered dinosaurs survived, and they are the birds we see today. Mammals, small and nocturnal, inherited the empty world and grew into elephants, whales and humans.
- First dinosaurs: about 240 million years ago
- Jurassic peak of giants: 200–145 million years ago
- T. rex lived: 68–66 million years ago
- Asteroid impact: 66 million years ago
- Birds: living dinosaurs today