Dinosaurs came in many different sizes and shapes. Birds are dinosaurs. They are still alive today. They stood with their legs straight under their bodies. Lizards sprawl instead.

The age of the dinosaurs was the Mesozoic Era. It had three periods. They were the Triassic, the Jurassic and the Cretaceous. As of November 2026, the Cretaceous Period ended about 66 million years ago, with the mass extinction that closed the age of the dinosaurs.

Birds evolved from small meat-eating dinosaurs called theropods. Some of the earliest dinosaurs were small two-legged hunters. One was Eoraptor from Argentina.

T. rex had about 60 big, sharp teeth. It had a good sense of smell. A large part of its brain handled smells. As of November 2026, it had the strongest bite of any known land animal.

Triceratops had three horns on its big skull. Stegosaurus defended itself by swinging its spiked tail. The first scientist to describe Stegosaurus thought its plates lay flat on its back.

Brachiosaurus was huge. It had four legs, a long neck and a long tail. It ate plants. It fed on leaves from tall trees.

Spinosaurus had short legs. It may have spent a lot of its time living in and around water. It ate fish. The shape of its narrow jaws was good for trapping them.

Some fossils keep impressions of the skin. These can show scales. Dinosaurs left fossil dung. It gives clues about what they ate.

Velociraptor was small. It ate meat. It was about the size of a turkey. It had feathers, but it could not fly. Microraptor was tiny. It had feathers. It was about the size of a crow.

A giant asteroid hit Earth about 66 million years ago. As of November 2026, scientists link it to their end. As of November 2026, about three quarters of the animals on Earth died out in the mass extinction. It was not only the dinosaurs. Birds were the only dinosaurs that survived.

Words to know

• sprawl: spread out sideways
• periods: spans of time
• defended: kept safe
• asteroid: space rock

The short version

The age of the dinosaurs was the Mesozoic Era, with three periods: the Triassic, the Jurassic and the Cretaceous. As of November 2026, the Cretaceous Period ended about 66 million years ago, with the mass extinction that closed the age of the dinosaurs. Birds are dinosaurs that are still alive today.

Quick facts

• Dinosaurs stood with their legs straight under their bodies, unlike lizards and crocodiles, which sprawl.
• Birds evolved from small meat-eating dinosaurs called theropods.
• Tyrannosaurus rex had about 60 big, sharp teeth.
• Dinosaurs left fossil dung, and it gives clues about what they ate.