Bellemite “pendulum” and pendant, from Morocco.

Fossils are all remains and traces of plants and animals that are preserved in rocks. Although it is often thought that fossils must be 'petrified', this is not always the case. Many fossils are not petrified and even very old rocks contain fossil remains that have hardly changed. The idea that fossils are always very old is also incorrect. Many young fossils are known, originating in a period when people were already on earth. The science that studies fossils is called paleontology. This area of ​​knowledge helps in the study of rock sequence, a branch of geology called biostratigraphy. Because remains of life only fossilize under specific conditions, fossil information is limited and by definition incomplete. When we hear the word fossil, people often think of the bones of dinosaurs or mammoths. Indeed, the hard parts of an organism have the greatest chance of being preserved through fossilization. For vertebrates these are the bones and especially the teeth. Softer tissues are only preserved in special cases and are therefore much rarer. They are only kept if they quickly become buried under a layer that protects them against rotting or damage. With only the hard parts it is sometimes difficult to form a good picture of the complete organism. A good example of this is the Conodonta, which for a long time were only known for their teeth. Only when a print of the rest of such an animal was found did it become apparent that it was a primitive form of the tribe Chordata. In other animal groups, other hard parts, such as shells, are often fossilized.