Triassic, Jurassic, Cretaceous — three ages on one planet
Short answer: dinosaurs lived a very long time, but not all at once. First Triassic, then Jurassic, then Cretaceous. Three long chapters of one book, not one day. Stegosaurus is Jurassic. T. rex is the very end of the Cretaceous. They only share a frame in movies. On our cards each one has its own years. Look at those.
Three chapters, not one “age of dinosaurs”
People say “dinosaurs” as if they were one class in one school. More than a hundred and fifty million years went by. Species came and went, like people in different centuries.
Easy to remember: the Triassic started about 250 million years ago, the Jurassic about 200, the Cretaceous about 145. The Cretaceous ended 66 million years ago, when the asteroid hit. That is in the extinction guide.
Triassic: the first ones, not the giants yet
The Triassic started after a huge disaster: almost everything alive had already ended once. Earth was one giant land. Hot and dry.
The first dinosaurs were still small. Not our Brachiosaurus. Not T. rex. They are only beginning. If you draw “the very start,” do not put Diplodocus in the shot. He is not here yet.
Jurassic: long necks and plates on the back
The Jurassic is the chapter of long-neck giants and Stegosaurus. Brachiosaurus on the card is 25 metres and about 50 tonnes — a four-storey building. Diplodocus is 27 metres. Stegosaurus is nine metres, plates on the back, a brain the size of a walnut.
Archaeopteryx is half a metre, also Jurassic: feathers already, teeth still. No T. rex in the Jurassic. If a cartoon has Stegosaurus running from T. rex, that is a ticket, not a bone.
Cretaceous: horns, sails and the king
The Cretaceous is long. At the start our T. rex is not here. At the end — yes: 12 metres, 8 tonnes, 68–66 million years ago. Next to him, Triceratops, nine metres. Velociraptor is two metres, a turkey, a few million years before T. rex.
Spinosaurus with the sail is Cretaceous too, but earlier than the king. Pteranodon flew in the Cretaceous and is still not a dinosaur. That is another guide.
How not to mix them up
Ask: “Jurassic or Cretaceous?” Jurassic — necks and plates. Cretaceous — horns and our T. rex. Triassic — small first ones, none of the famous giants from the cards.
Three cards in a row: Brachiosaurus, Stegosaurus, T. rex. Two Jurassic, one Cretaceous. The age sticks better that way than the word “Mesozoic.”
Questions kids ask
- How are Triassic, Jurassic and Cretaceous different?
- Three times in a row. Different animals. Stegosaurus is Jurassic. T. rex is the end of the Cretaceous. They did not live together.
- When was the Jurassic?
- About 200 to 145 million years ago. Then the Cretaceous started.
- Did T. rex live in the Jurassic?
- No. He is from the very end of the Cretaceous, about 66 million years ago.
- Why is everyone together in Jurassic Park?
- Brighter that way. In the bones they only share being dinosaurs. The time is different.
- Which period lasted longest?
- The Cretaceous lasted longer than the Jurassic. That is why it has many animals, not only T. rex.
- Did people live with dinosaurs?
- No. People came much, much later. Between T. rex and us there are still tens of millions of years.
Remember this
- Label the age on a drawing. “Just a dinosaur” mixes Stegosaurus with T. rex.
- Jurassic Park is a movie title, not a timetable of bones.
- Three cards: Brachiosaurus (Jurassic), Stegosaurus (Jurassic), T. rex (Cretaceous).