- mold fossils (a fossilized impression made in the substrate - a negative image of the organism) this here is a picture of a mold fossil (on the left )
- cast fossils (formed when a mold is filled in) (on the right)
- trace fossils = ichnofossils (fossilized nests, gastroliths, burrows, footprints, etc.)
- true form fossils (fossils of the actual animal or animal part).