- Body fossils include fossils that retain some part of the organism. These include fossils where the organic matter remains intact, such as with dinosaur bones. This category also includes fossils that are molds of an organism and display the body or skeletal structure, but lack any remaining organic matter.
- Trace fossils, also know as Ichnofossils, are preserved impressions left by an organism. These fossils do not reveal much about the structure of the organism, but can revel things about its habitat, activities or diet. Footprints, plant impressions and preserved excrement are types of trace fossils.
- Molecular fossils are made of preserved organic matter that have become a fossil or significantly decayed. These fossils retain the original molecular structure of the organism, but have undergone a chemical change. Therefore these fossils are very delicate. When studied they can revel the makeup of an organism's DNA or other organic molecules.
- Some fossils qualify as index fossils. These are fossils that can be used to identify a certain period of geologic time. Qualifications for index fossils include easy recognition, abundance, a wide geographic range and a short ecological span in which the organism lived. Hard body parts such as shells, bones and teeth make good index fossils because they are preserved better than soft tissue.
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