Fossils are the remains of organisms over 10 000 years old. Because all organisms are slowly but continuously evolving fossils differ from living species. Many fossils are those of extinct species who have no living relatives. By examining the structure of fossils in conjunction with a number of dating techniques it is possible to construct family trees for living and extinct species. It is important to remember that there will always be some gaps in the fossil record because fossilisation can only occur in certain (rare ) geological conditions. So organisms who did not live in such environments will probably never be found.
Fossil Trilobites ( 200 mya)
Trilobites were extremely common throughout all the oceans but disappeared as fish started to evolve.
Fossil Archaeopteryx (150 mya)
This is a very famous fossil which shows both reptillian and bird charectoristics. It provides strong evidence that birds evolved from a species of dinosaur. This has since been confirmed through studies of bird and reptile DNA which are very similar.
Reconstructions of Archaeopteryx
Reconstruction of Pterosaur
