Editing Fossil (section)

=== Adpression (compression-impression) ===
[[Compression fossil]]s, such as those of fossil ferns, are the result of chemical reduction of the complex organic molecules composing the organism's tissues. In this case, the fossil consists of original material, albeit in a geochemically altered state. This chemical change is an example of [[diagenesis]]. What remains is often a [[carbonaceous film]] known as a phytoleim, in which case the fossil is known as a compression. Often, however, the phytoleim is lost and all that remains is an impression of the organism in the rock—an impression fossil. 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. For this reason, one term covers the two modes of preservation: ''adpression''.<ref name="ShuteCleal 1986">{{cite journal|last1=Shute |first1=C. H. |last2=Cleal |first2=C. J. |year=1986 |journal=Geological Curator |volume=4 |title=Palaeobotany in museums |issue=9 |pages=553–559|doi=10.55468/GC865 |s2cid=251638416 |doi-access=free }}</ref>

==== Carbonization and coalification ====
Fossils that are carbonized or coalified consist of the organic remains which have been reduced primarily to the chemical element carbon. Carbonized fossils consist of a thin film which forms a silhouette of the original organism, and the original organic remains were typically soft tissues. Coalified fossils consist primarily of coal, and the original organic remains were typically woody in composition.

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File:Probable leech from the Waukesha Biota.jpg|Carbonized fossil of a [[cycloneuralia]]n worm that was once misidentified as a [[leech]]<ref>{{Cite journal |last1=Braddy |first1=Simon J. |last2=Gass |first2=Kenneth C. |last3=Tessler |first3=Michael |date=2023-09-04 |title=Not the first leech: An unusual worm from the early Silurian of Wisconsin |url=https://www.cambridge.org/core/journals/journal-of-paleontology/article/not-the-first-leech-an-unusual-worm-from-the-early-silurian-of-wisconsin/2AB9EDAF214C38A8EE93C260BAC9878D |journal=Journal of Paleontology |volume=97 |issue=4 |language=en |pages=799–804 |doi=10.1017/jpa.2023.47 |bibcode=2023JPal...97..799B |s2cid=261535626 |issn=0022-3360}}</ref> from the Silurian [[Waukesha Biota]] of Wisconsin.
File:Lycopod axis.jpg|Partially coalified axis (branch) of a [[lycopod]] from the Devonian of [[Wisconsin]].
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