Dinosaurs

Dinosaurs were a diverse group of reptiles that dominated life on land for more than 150 million years, during the Mesozoic Era. They first appeared in the Triassic period, flourished through the Jurassic and Cretaceous periods, and ranged from small creatures the size of a chicken to some of the largest animals ever to walk the Earth. They are defined by particular features of the skeleton, especially in the hips and limbs, which set them apart from other prehistoric reptiles.

Everything known about dinosaurs comes from fossils — the preserved remains and traces of ancient life found in rock. Bones, teeth and eggs reveal the animals' size and structure, while trace fossils such as footprints record how they moved and behaved. The scientists who study them, palaeontologists, reconstruct the appearance, diet and lifestyle of long-extinct species from these clues. Well-known dinosaurs include the large predator Tyrannosaurus rex, the long-necked plant-eating sauropods, the horned and plated herbivores, and a variety of smaller, agile hunters.

Most dinosaur groups died out at the end of the Cretaceous period, in a mass extinction widely linked to the impact of a large asteroid together with other environmental changes. However, one lineage survived: birds are descended from small feathered dinosaurs and are considered living dinosaurs by scientists. The study of these animals also touches on related fields such as palaeoecology, the study of ancient environments, and palaeoclimatology, the study of past climates.

Frequently asked questions

When did dinosaurs live?

They lived during the Mesozoic Era, appearing in the Triassic period and thriving through the Jurassic and Cretaceous, a span of well over 150 million years.

How do we know what dinosaurs were like?

Knowledge comes from fossils — preserved bones, teeth, eggs and footprints — which palaeontologists study to reconstruct the animals' size, diet and behaviour.

Are any dinosaurs alive today?

Birds descend from small feathered dinosaurs and are regarded by scientists as living dinosaurs; the other groups died out at the end of the Cretaceous.