In this case the fossil consists of original material, albeit in a geochemically altered state.
is any preserved remains, impression, or trace of any once-living thing from a past geological age.
Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, hair, petrified wood, oil, coal, and DNA remnants.
Fossils may also consist of the marks left behind by the organism while it was alive, such as animal tracks or feces (coprolites).
These types of fossil are called trace fossils or ichnofossils, as opposed to body fossils.
In many cases, however, compressions and impressions occur together.
For instance, when the rock is broken open, the phytoleim will often be attached to one part (compression), whereas the counterpart will just be an impression.to dinosaurs and trees, many meters long and weighing many tons.A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates, or the chitinous or calcareous exoskeletons of invertebrates.If this happens rapidly before significant decay to the organic tissue, very fine three-dimensional morphological detail can be preserved.Nodules from the Carboniferous Mazon Creek fossil beds of Illinois, USA, are among the best documented examples of such mineralization.For this reason, one term covers the two modes of preservation: adpression.