Fossils are often the only clues to animals and plants that lived millions of years ago. But how were they made?
Fossils are the remains of prints of animals and plants that have been preserved in rocks. Quite often, only the hard parts of an animal, such as the teeth or bones, are left. The rest has rotted away. But even when nothing remains of an animal, it may have left a hollow, the exact shape of its body, in the rock. Sometimes an animal left a footprint when it walked in soft sand or mud. A single footprint may be all that remains of an animals that was as big as four cars. Fossils can take millions of years to form.
How a dinosaur became a fossil
- When a dinosaur died, its body may have fallen, or washed, into a river.
- The dead body lay on the bottom of the river and the flesh rotted away.
- The skeleton was gradually buried under mud, and minerals from the water seeped into the bones and preserved them. Over millions of years, the mud turned into layers of rock and the dinosaur skeleton become a fossil.
- Millions of years alter, the sea level dropped. The wind and rain wear away the rock revealing the fossil: proof that dinosaurs once lived.
The Fossil Detectives
The scientists who do all the detective work on fossils are called paleontologists (pay-lee-on-toll-o-jists). They have found fossils all over the world. Their job can be very difficult because the fossil bones are often scattered in pieces. Only very rarely is a whole skeleton preserved in the rocks. Paleontologists identify the fossil bones, remove them from the ground, put them together, like a jigsaw, and decide how old they are. You can see the results of their works in natural history museums where dinosaur fossils are mounted and put on display.
Fossil bones and teeth are not the only clues that these giants of the past left behind them. Dinosaur footprints and the imprint of scaly skin, made in soft mud millions of years ago have also been found. Some of the most remarkable fossils found are dinosaurs droppings. Scientists grind up dinosaur droppings or coprolites into fine dust to find out what dinosaurs ate.