Why Pteranodon and Plesiosaurus are not dinosaurs
Pteranodon was a pterosaur, a flying reptile. Plesiosaurus was a sea reptile. Both lived in the Mesozoic Era, but neither belonged to the dinosaur group. They are in this encyclopedia because the story of prehistoric life would be incomplete without them.
What makes an animal a dinosaur?
Scientists sort animals by their ancestors and by the features they share, such as the way their bones are built. Being big, ancient or scaly is not enough to make an animal a dinosaur.
Tyrannosaurus, Triceratops and Stegosaurus all belong to the dinosaur group. Pterosaurs and plesiosaurs have family histories of their own.
Pteranodon and its wings
Pteranodon lived in the Cretaceous. Each of its wings was a membrane of skin held up by one enormously long finger. That is quite unlike the feathered wing of a bird.
It could soar over the sea and feed on fish. Pterosaurs were relatives of the dinosaurs, but they formed a separate group.
Plesiosaurus and its flippers
Plesiosaurus lived in the seas of the Jurassic. It had a long neck and four flippers to move itself through the water.
Where an animal lives does not decide which family it belongs to. Spinosaurus ate fish and spent time around water, and it was still a dinosaur. Plesiosaurus sat on a different branch of the reptiles.
Clues in a picture
You can spot Pteranodon by its membrane wings and the crest on its head. Plesiosaurus gives itself away with a long neck and four flippers.
For other prehistoric animals, read the name and the group on the card. A drawing on its own can sometimes fool you.
Why they share this encyclopedia
Dinosaurs, pterosaurs and sea reptiles all shared the living world of the Mesozoic. Putting them side by side shows how differently prehistoric animals lived.
They weren’t all alive at the same time, though, so look at the dates on the cards, not just the group.
Questions kids ask
- Was Pteranodon a dinosaur?
- No. It was a pterosaur, a flying reptile related to the dinosaurs.
- Was Plesiosaurus a dinosaur?
- No. It belonged to a group of sea reptiles called plesiosaurs.
- Which prehistoric animals could fly?
- Pterosaurs could, and so could some early birds. The birds belong to the dinosaur group.
- Was Spinosaurus a dinosaur even though it spent time near water?
- Yes. What counts is an animal’s ancestry and the features it shares with its relatives, not just where it lived.
- Why are they shown together in films?
- Films like to bring well-known prehistoric animals together. In reality they were not all related, or alive at the same time.
- How can a bird be a dinosaur but Pteranodon not be one?
- Birds evolved inside the dinosaur group. Pterosaurs evolved on a separate branch.
Remember this
- Compare Pteranodon’s membrane wing with a bird’s feathered wing.
- The legendary Loch Ness monster is sometimes drawn like a plesiosaur. That does not prove the creature exists.
- Try sorting three cards: T. rex is a dinosaur; Pteranodon and Plesiosaurus are not.