Tyrannosaurus rex had about 60 big, sharp teeth. As of November 2026, T. rex had the strongest bite of any known land animal. T. rex had a good sense of smell. A large part of its brain handled smells. A T. rex skeleton in Chicago is named Sue. It is about 13 feet tall at the hip. It is more than 40 feet long. As of November 2026, T. rex lived in North America late in the Cretaceous. That was about 68 to 66 million years ago.

Diplodocus and Brachiosaurus were huge plant-eaters. They had four legs, long necks and long tails. Brachiosaurus fed on leaves from tall trees. Dinosaurs stood with their legs straight under their bodies. Lizards and crocodiles sprawl. As of November 2026, Patagotitan is one of the largest land animals that has ever lived. As of November 2026, Patagotitan was probably about 120 feet (37 metres) long. No complete skeleton is known. So its exact length is uncertain.

Fossil dinosaur footprints are a kind of trace fossil. Most dinosaur trace fossils are footprints. Dinosaurs left fossil dung. It gives clues about what they ate. Some dinosaur fossils keep impressions of the skin. These can show scales. Becoming a fossil is rare. So we know from fossils only a tiny share of all the dinosaurs that ever lived. Most fossils found are of sea animals such as shellfish. So a fossil of a big land animal is unusual.

The scientist who first described Stegosaurus thought its plates lay flat on its back. Early scientists put the spiky thumb bone of Iguanodon on its nose like a horn. Better fossils showed it belonged on its hand. Brontosaurus was thought to be the same dinosaur as Apatosaurus for about a hundred years. A 2015 study found it was a separate kind. The first Archaeopteryx fossil was found in Germany in 1861. It was a surprise. No birds were known from so far back.

Scientists still are not sure why Stegosaurus had its back plates. Ideas include protecting it from predators. Another idea is helping it control its body heat. Triceratops had three horns on its big skull. Pachycephalosaurus had a thick bony dome on top of its head. Parasaurolophus had a long hollow crest on its head. Tubes inside ran from its nostrils through the crest. Scientists think it could make loud sounds by blowing air through its hollow crest.

A giant asteroid hit Earth about 66 million years ago. As of November 2026, scientists link it to the end of the dinosaurs. As of November 2026, about three quarters of the animals on Earth died out. That was in the mass extinction 66 million years ago. It was not only the dinosaurs. The same mass extinction ended the flying pterosaurs and many sea animals. Huge volcanic eruptions were going on in what is now India. This was around the time the dinosaurs died out. They made a lava outcrop called the Deccan Traps. Birds were the only dinosaurs that survived.

Words to know

• crest: head ridge
• unusual: not common
• predators: hunting animals