History › Complex life
Age of dinosaurs
c. 230–66 million years ago· Event· Life & early humans
Well documentedSolid records, physical evidence or scientific consensus.
Non-bird dinosaurs lasted about 165 million years and dominated life on land for most of the Jurassic and Cretaceous periods.
See it on the History map →What happened
Dinosaurs appeared about 230 million years ago; the earliest known fossils come from Argentina and Brazil. They took over after another extinction about 201 million years ago. They ranged from chicken-sized hunters to plant-eaters over 30 m (100 feet) long. Flowering plants spread late in their reign. Birds evolved from small feathered dinosaurs, so dinosaurs never fully died out. The Curious Life map goes deeper.
Why it matters
They show how one group can dominate a planet for an immense span, and their sudden end opened the world to mammals, including us.
How we know
Fossils on every continent, named 'dinosaurs' by Richard Owen in 1842; feathered dinosaurs found in Liaoning, China, since the 1990s confirm the link to birds.
Still debated
Whether dinosaurs were already declining before the asteroid hit, and how warm-blooded they were, are still argued.
Inside this (4)
Connections (3)
▸Supercontinent Pangaea was the world of the early Age of dinosaursWell documented
The connection
When dinosaurs appeared about 230 million years ago, nearly all land was joined in Pangaea. With no oceans to cross, early dinosaurs spread across the supercontinent. As Pangaea broke apart, separated dinosaur groups evolved in different directions, producing the varied types of the Jurassic and Cretaceous.
When and how
Across Pangaea in the Triassic Period, about 230–200 million years ago; the earliest fossils come from Argentina and Brazil.
How we know
Similar early dinosaur fossils turn up on continents now far apart, such as South America, Africa and India.
Debates and open questions
How much Pangaea's hot, dry interior limited where early dinosaurs could live is debated.
▸Permian extinction ('the Great Dying') cleared the way for Age of dinosaursWell documented
The connection
By wiping out most land animals, including the dominant mammal relatives, the Great Dying left empty roles in nature. In the recovery, reptile groups diversified rapidly, and dinosaurs appeared about 20 million years later. A second extinction about 201 million years ago then let them dominate.
When and how
Worldwide, during the Triassic Period, between about 252 and 201 million years ago.
How we know
Fossils show mammal relatives declining after the extinction while reptile groups, including dinosaur ancestors, spread.
Debates and open questions
Dinosaurs took millions of years to rise; how much that owed to the Great Dying versus later climate shifts is debated.
▸K–Pg mass extinction (asteroid impact) ended Age of dinosaursWell documented
The connection
The asteroid impact at Chicxulub caused wildfires and a global 'impact winter' that shut down plant growth. Large animals that needed lots of food, like dinosaurs, starved. All dinosaurs except early birds died out, ending their reign of about 165 million years.
When and how
Worldwide, 66 million years ago, starting at the impact site off Mexico's Yucatán Peninsula.
How we know
A global iridium-rich layer marks the boundary; no non-bird dinosaur fossils are found above it; the crater's age matches precisely.
Debates and open questions
Whether some dinosaurs survived briefly after the impact, and how much volcanoes contributed, are debated.