When Did Dinosaurs Live? The Mesozoic Era Explained

Non-avian dinosaurs existed for approximately 165 million years, emerging during the Carnian stage of the Late Triassic period (about 233 million years ago) and perishing at the Cretaceous-Paleogene (K-Pg) boundary roughly 66 million years ago.

The Mesozoic Era Tripartite Division

1. The Triassic Period (251.9 – 201.3 Ma): Following the devastating Permian-Triassic extinction, early dinosaurs emerged as nimble, bipedal archosaurs such as Herrerasaurus and Eoraptor in the southern Pangaean landmass.

1. The Jurassic Period (201.3 – 145.0 Ma): As the supercontinent Pangaea fractured into Laurasia and Gondwana, warm greenhouse conditions allowed sauropodomorphs and megalosauroids to attain colossal dimensions.

1. The Cretaceous Period (145.0 – 66.0 Ma): Marked by maximum floral diversification, including the appearance of flowering angiosperms, specialized ceratopsians, duck-billed hadrosaurs, and tyrannosaurids.

By contrast, human ancestors (genus Homo) have existed for roughly 2.8 million years—meaning the temporal span separating Tyrannosaurus rex from Stegosaurus (approx. 83 million years) is greater than the temporal span separating T. rex from modern humans (approx. 66 million years).