Dinosaur fossils

Fossils are the preserved remains or traces of ancient organisms, and they are the only direct evidence of dinosaurs, which died out long before any human record. A fossil typically forms when an animal is buried quickly by sediment after death; over very long periods, minerals seep into the buried bone and gradually replace its original material, turning it to stone while preserving its shape. The surrounding sediment hardens into rock, and much later erosion or excavation may expose the fossil again.

Several kinds of fossils inform the study of dinosaurs. Body fossils — bones, teeth, claws, eggs and, rarely, impressions of skin or feathers — show what the animals looked like and how their skeletons were built. Trace fossils, such as footprints, trackways, nests and fossilised droppings, record behaviour: how a dinosaur walked, whether it moved in groups, and what it may have eaten. The age of a fossil is estimated from the rock layers in which it lies, since deeper layers are generally older, and from techniques that date the surrounding rock.

Important fossil discoveries have been made on every continent, with certain regions yielding especially rich beds of well-preserved specimens. Palaeontologists excavate, clean and study these finds to reconstruct extinct species and the environments they lived in. Each new fossil can refine or revise the scientific picture of how dinosaurs looked, moved and were related to one another, and to their living descendants, the birds.

Frequently asked questions

How does a dinosaur bone become a fossil?

After the animal is buried in sediment, minerals slowly replace the bone over long periods, turning it to stone while keeping its original shape.

What is the difference between body and trace fossils?

Body fossils are remains such as bones, teeth and eggs, while trace fossils are records of activity, such as footprints, nests and droppings.

How are fossils dated?

Their age is estimated from the position of the rock layers containing them, with deeper layers generally older, and from methods that date the surrounding rock.