Were Dinosaurs Reptiles?
Yes! Dinosaurs were reptiles, just like turtles, lizards and crocodiles. But they were a very special kind. Climb the reptile family tree and find out what made dinosaurs different.
Quick Answer
Yes, dinosaurs were reptiles. They belong to the same big family as turtles, lizards, snakes and crocodiles. But dinosaurs were a special kind of reptile: they stood with their legs straight under their bodies, many had feathers, and many were probably warm-blooded. And because birds are dinosaurs, the robin outside your window is a reptile too!
What Makes an Animal a Reptile?
When you learn about animals in school, reptiles usually come with a checklist. A reptile has a backbone, scaly skin, and lays eggs with a shell on land (not jelly eggs in water like a frog). Dinosaurs tick every box. Scientists have found dinosaur eggs all over the world, and fossils like the Edmontosaurus “mummy” still show the shape of their scales.
Scientists today also use a second test: who are your relatives? They sort animals like a giant family tree. Every animal that comes from the first reptiles is a reptile, even if it changed a lot over time. Dinosaurs pass this test too.
| Reptile check | 🦎 Lizard | 🦖 Dinosaur |
|---|---|---|
| Has a backbone | ✅ Yes | ✅ Yes |
| Lays eggs with a shell, on land | ✅ Yes | ✅ Yes |
| Scaly skin | ✅ Yes | ✅ Yes, and many had feathers too |
| Comes from the reptile family tree | ✅ Yes | ✅ Yes |
| Legs | ↔️ Stick out to the sides | ⬇️ Straight under the body |
| Warm or cold? | 🧊 Cold-blooded | 🔥 Many were probably warm-blooded |
The first four rows say “reptile!” The last two are what made dinosaurs special.
The Reptile Family Tree
The reptile family has a few big branches. Turtles are on one. Lizards and snakes share another. And then there are the archosaurs (say it: AR-koh-sorz, “ruling reptiles”), which showed up about 250 million years ago. The archosaurs split into crocodiles, pterosaurs and dinosaurs. Much later, one group of small, feathered dinosaurs gave rise to birds.
What Made Dinosaurs Different From Other Reptiles?
So if a dinosaur is a reptile, and a gecko is a reptile, what made a dinosaur a dinosaur? Scientists look for these clues:
They stood up tall
A dinosaur's legs went straight down under its body, like pillars. Lizards and crocodiles crawl with their legs bent out to the sides. Standing tall helped dinosaurs walk and run for a long time without getting tired.
A hole in the hip
The hip socket of a dinosaur had a hole right through the middle. Scientists use this clue to tell a dinosaur skeleton from any other reptile's.
Lots of them had feathers
Many dinosaurs, like Velociraptor, were covered in fluffy feathers. No lizard, snake or turtle has ever grown a feather. Meet them on our feathered dinosaurs page.
Many were warm inside
Today's lizards warm up by lying in the sun. Many dinosaurs probably made their own body heat, like birds and mammals do. More on that below!
Were Dinosaurs Cold-Blooded Like Lizards?
A hundred years ago, people pictured dinosaurs as giant, slow lizards that dragged their tails and lay in the sun to warm up. Today scientists think many dinosaurs were warm-blooded, which means they made their own body heat, like birds and people do. Here are the clues:
- Fast-growing bones. Dinosaur bones have growth rings, like a tree. They show many dinosaurs grew quickly, the way warm-blooded animals do.
- Fluffy feathers. Feathers work like a warm coat, and you only need a coat if you make your own heat.
- Snowy homes. Dinosaurs lived near the North and South Poles, where winters were dark and cold. A sun-loving lizard couldn't live there.
- Their grandchildren are warm. Birds are warm-blooded, and they came from dinosaurs.
Scientists are still working out the details. Some dinosaurs were probably toasty like birds, while others may have been somewhere in between warm and cold. Either way, a warm-blooded reptile is still a reptile!
Prehistoric Reptiles That Weren't Dinosaurs
All dinosaurs were reptiles, but not every prehistoric reptile was a dinosaur. These famous animals often get called dinosaurs, but they're not:
Pterosaurs
The flying reptiles. They were the dinosaurs' closest cousins, but their wings were made of skin, not feathers. Learn more on our pterodactyl page.
Plesiosaurs and ichthyosaurs
Sea reptiles with flippers. They swam in the oceans while dinosaurs walked on land. Dive in with our water dinosaurs page.
Mosasaurs
Giant sea monsters that were actually swimming lizards! They are cousins of today's monitor lizards and snakes.
Crocodiles and alligators
They lived alongside dinosaurs and are still around today. Are alligators and crocodiles dinosaurs? No, but they're close cousins.
Dimetrodon
The sail-backed animal that comes in lots of dinosaur toy sets. Surprise: it wasn't a dinosaur or even a reptile! It lived before the dinosaurs and was a distant cousin of mammals, which means it was closer to you than to T. rex.
Wait, So Are Birds Reptiles Too?
Here's where it gets fun. Dinosaurs are reptiles. Birds are dinosaurs. So... birds are reptiles! Scientists who sort animals by family tree really do say this.
Your school book might still put birds in their own group, and that's okay too. It's just a different way of sorting. To see the clues that link a sparrow to T. rex, read Are Birds Dinosaurs? or meet the chicken, a living dinosaur.
Quiz: Reptile or Not?
Read each animal out loud and let your little one guess: reptile or not? Then tap to check the answer.
🐢 Turtletap to see
Reptile! But not a dinosaur. Turtles are on their own branch of the reptile family tree.
🦖 Triceratopstap to see
Reptile and dinosaur! It stood up tall on four pillar-like legs.
🐦 Pigeontap to see
Reptile and dinosaur, believe it or not! Birds are dinosaurs, so scientists who group animals by family tree count them as reptiles too.
🐸 Frogtap to see
Not a reptile. Frogs are amphibians. They lay soft, jelly-like eggs in water, and their skin is smooth and wet, not scaly.
🐊 Crocodiletap to see
Reptile! But not a dinosaur. It's the dinosaurs' close cousin.
🐬 Dolphintap to see
Not a reptile. Dolphins are mammals: they breathe air, drink milk as babies and are warm-blooded. Ichthyosaurs looked like dolphins, but they were reptiles!
Frequently Asked Questions
Were dinosaurs reptiles?
Yes. Dinosaurs were reptiles. They belong to a reptile group called the archosaurs, along with crocodiles and pterosaurs. Dinosaurs were a special kind of reptile, though: they stood with their legs straight under their bodies, many had feathers, and many were probably warm-blooded.
Are dinosaurs reptiles or mammals?
Dinosaurs are reptiles, not mammals. They laid eggs with hard shells, and they come from the reptile branch of the animal family tree. Mammals, like dogs and people, grow fur, feed their babies milk and come from a different branch.
Are dinosaurs lizards?
No. The word “dinosaur” means “terrible lizard,” but dinosaurs were not lizards. Lizards and dinosaurs are both reptiles, but they sit on different branches of the reptile family tree. A lizard's legs sprawl out to the sides, and a dinosaur's legs went straight down.
Were dinosaurs cold-blooded?
Probably not most of them. Scientists used to think dinosaurs were cold-blooded like lizards. Now, clues like fast-growing bones, feathers and dinosaurs living near the chilly North and South Poles show that many dinosaurs made their own body heat. Some may have been somewhere in between warm and cold.
Are birds reptiles?
It depends on how you sort animals. In school, birds are often taught as their own group. But scientists who sort animals by their family tree count birds as reptiles, because birds are dinosaurs, and dinosaurs are reptiles.
What is the closest living relative of dinosaurs?
Birds, because they are living dinosaurs. After birds, the closest relatives are crocodiles and alligators.
Did all dinosaurs have scales?
Many dinosaurs had scaly skin, and some fossils even show the pattern of their scales. But lots of dinosaurs had feathers, and some had both scales and feathers on different parts of their bodies.
All illustrations on this page are original Puffsaurus artwork.
Does your little one love dinosaurs? 🦕
Explore our dinosaur-themed nursery rhymes and kids' songs!