Ortoceras pot RECTANGULAR MODEL made in Erfoud Morocco.

Fossils are all remains and traces of plants and animals that are preserved in rock. Although it is often thought that fossils must be 'petrified', this is not always the case. Many fossils are not petrified and even from very old rocks fossil remains are known that have hardly changed. The idea that fossils are always very old is also incorrect. Many young fossils are known, formed in a period when people were already on earth. The science that studies fossils is called paleontology. This field of knowledge helps in the research of the sequence of rocks, a branch within geology called biostratigraphy. Because remains of life only fossilize under specific circumstances, fossil information is limited and by definition incomplete. When people think of the word fossil, they often think of the bones of dinosaurs or mammoths. Indeed, the hard parts of an organism have the greatest chance of being preserved by 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 preserved if they are quickly buried under a layer that protects them from rotting or being eaten. With only the hard parts, it is sometimes difficult to form a good picture of the complete organism. A good example of this are the Conodonta, which for a long time were only known from their teeth. Only when an impression of the rest of such an animal was found, it turned out that it was a primitive form of the phylum Chordata. In other animal groups, other hard parts, such as shells, are often fossilized.