How long were dinosaurs around?

The first dinosaurs appeared about two hundred and forty-five million years ago, in a time called the Triassic. Then came the Jurassic, and then the Cretaceous. When the big ones were gone, sixty-six million years ago, they had been around for more than a hundred and seventy million years!

How do scientists know how old a fossil is?

Rock builds up in layers, so the oldest layers are at the bottom and the youngest are on top. Sometimes a volcano drops a layer of ash, and scientists can work out the age of ash very well. Find dated ash above a fossil and below it, and the fossil's age sits between the two.

When did dinosaurs live?

Tiny answers for ages 4–11, then goes 2 steps deeper each time a child asks why.

Tiny says

Think of your grandma's grandma, and her grandma, and keep going back. Go back millions and millions of years, long before there were any people at all. There they are: dinosaurs! The big ones were gone millions of years before the first people came along.

For ages 4–7

Checked against When did dinosaurs live? (Natural History Museum)
How long were dinosaurs around?

The first dinosaurs appeared about two hundred and forty-five million years ago, in a time called the Triassic. Then came the Jurassic, and then the Cretaceous. When the big ones were gone, sixty-six million years ago, they had been around for more than a hundred and seventy million years!

For ages 6–9

Checked against When did dinosaurs live? (Natural History Museum)
How do scientists know how old a fossil is?

Rock builds up in layers, so the oldest layers are at the bottom and the youngest are on top. Sometimes a volcano drops a layer of ash, and scientists can work out the age of ash very well. Find dated ash above a fossil and below it, and the fossil's age sits between the two.

For ages 8–11

Checked against Dating dinosaurs and other fossils (Australian Museum)