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A dinosaur skeleton

A dinosaur skeleton: evolution of dinosaurs

When did dinosaurs evolve?

The first dinosaurs evolved out of earlier types of chordate reptiles about 230 million years ago, on the big land mass called Pangaea.

Earlier chordates
More about reptiles
The Triassic period
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Cold-blooded or warm-blooded?

Dinosaur eggs: evolution of dinosaurs

At that time, all of the land on earth was stuck together in one big continent. The huge expanse of land meant it got very warm in the middle.

Plate tectonics and Pangaea
Why did dinosaurs lay eggs?

Like other reptiles, dinosaurs were generally cold-blooded (they got most of their body heat from the sun). They laid eggs and waited for them to hatch. Some dinosaurs were warm-blooded, or partly warm-blooded.

How big were the biggest dinosaurs?

Some dinosaurs gradually evolved to be bigger than any animal had ever gotten before, and bigger than any mammal today.

Evolution of mammals
A project with feathers

Big dinosaurs like the ultrasaurus had more than 1000 trillion cells in them. They may have weighed as much as fifty tons – that’s a little more than a loaded semi truck. Other dinosaurs were much smaller, the size of chickens, and some of them could fly. Some – maybe most – dinosaurs had feathers.

What did dinosaurs eat?

dinosaur skeleton with a big head

Tyrannosaurus Rex (American Museum of Natural History): evolution of dinosaurs

Some dinosaurs ate only plants, while other dinosaurs like Tyrannosaurus Rex ate meat – mainly from other dinosaurs, but they also ate the small mammals that were around after about 200 million years ago.

What kind of plants were there?

What happened to the dinosaurs?

Dinosaurs lasted a long time, but about 65 million years ago, at the end of the Cretaceous period, most of the dinosaurs died. Probably a big meteor hit the Earth from space. The huge dust cloud raised by the meteor blocked so much sunlight that Pangaea got too cold for the dinosaurs.

What is a meteor?
A meteors project
Evolution of birds
The Cretaceous period

The only kind of dinosaurs that lived through this cold period was a small kind with feathers that evolved into modern birds, becoming warm-blooded like mammals, and developing beaks instead of teeth. But birds still lay eggs like dinosaurs.

Did you find out what you wanted to know about the evolution of dinosaurs? Let us know in the comments!

More about reptiles

And more about birds

More about chordates

Bibliography and further reading about the evolution of dinosaurs:

More about reptiles

And more about birds

More about chordates
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