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Introduction - photo "FossilFernLeavesPennsylvanianOhio.jpg" - size parameter - changed to "upright=1.35" - see WP:IMAGESIZE |
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[[Image:FossilFernLeavesPennsylvanianOhio.jpg|upright=1.35|thumb|Fossil [[seed fern]] leaves from the Late [[Carboniferous]] of northeastern [[Ohio]].]]
A '''compression fossil''' is a [[fossil]] preserved in [[sedimentary rock]] that has undergone [[compression (physical)|physical compression]]. While it is uncommon to find [[animal]]s preserved as good compression fossils, it is very common to find [[plant]]s preserved this way. The reason for this is that physical compression of the rock often leads to
The best fossils of [[leaf|leaves]] are found preserved in fine layers of [[sediment]] that have been compressed in a direction [[perpendicular]] to the plane of the deposited sediment.<ref name="Arnold 1947"/> Since leaves are basically flat, the resulting distortion is minimal. [[Plant stem]]s and other three-dimensional plant structures do not preserve as well under compression. Typically, only the basic outline and surface features are preserved in compression fossils; internal [[anatomy]] is not preserved. These fossils may be studied while still partially entombed in the sedimentary rock matrix where they are preserved, or once lifted out of the matrix by a peel or transfer technique.<ref name="Stewart 1993"/>
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==Slabs==
[[File:Pterodactylus antiquus p and cp.jpg|
{{multiple image
| align = right
| direction = horizontal
| image1 = Longipteryx chaoyangensis (BMNHC Ph930A) NMNS.jpg
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| image2 = Longipteryx chaoyangensis (BMNHC Ph930B) NMNS.jpg
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| footer = Slab (left) and counter slab (right) of ''[[Longipteryx]]''
}}
A slab and counter slab, more often called a part and counterpart in paleoentomology<ref name="Jepson2011">{{cite journal |last1=Jepson |first1=J.E. |last2=Ansorge |first2=J. |last3=Jarzembowski |first3=E.A. |year=2011 |title=New snakeflies (Insecta: Raphidioptera) from the Lower Cretaceous of the UK, Spain and Brazil |journal= Palaeontology |volume=54 |issue=2 |pages=385–395 |doi=10.1111/j.1475-4983.2011.01038.x|bibcode=2011Palgy..54..385J |doi-access=free }}</ref> and paleobotany,<ref name="Channing2011">{{cite journal |last1=Channing |first1=A. |last2=Zamuner |first2=A. |last3=Edwards |first3=D. |last4=Guido |first4=D. |year=2011 |title=''Equisetum thermale'' sp. nov. (Equisetales) from the Jurassic San Agustin hot spring deposit, Patagonia: Anatomy, paleoecology, and inferred paleoecophysiology. |journal= American Journal of Botany |volume=98 |issue=4 |pages=680–697 |doi= 10.3732/ajb.1000211 |pmid=21613167|bibcode=2011AmJB...98..680C |doi-access=free |hdl=11336/95234 |hdl-access=free }}</ref> are the matching halves of a compression fossil, a fossil-bearing [[Matrix (geology)|matrix]] formed in [[sedimentary]] deposits. When excavated the matrix may be split along the natural grain or cleavage of the rock. A fossil embedded in the sediment may then also split down the middle, with fossil remains sticking to both surfaces, or the counter slab may simply show a negative impression or mould of the fossil.<ref>[http://www.proz.com/kudoz/english_to_polish/archaeology/762880-slab_counter_slab.html ProZ]</ref> Comparing slab and counter slab has led to the exposure of a number of fossil forgeries.
Differences between the impressions on slab and counterslab led astronomer [[Fred Hoyle]] and applied physicist [[Lee Spetner]] in 1985 to declare that some ''[[Archaeopteryx]]'' fossils had been [[Archaeopteryx#Controversy|forged]], a claim dismissed by most palaeontologists.<ref>[https://books.google.com/books?id=gWtV-9zG8ycC
In its November 1999 edition, ''[[National Geographic Magazine|National Geographic]]'' magazine announced the discovery of ''[[Archaeoraptor]]'', a link between dinosaurs and birds, from a 125 million-year-old fossil that had come from [[Liaoning Province]] of China. Chinese palaeontologist [[Xu Xing (paleontologist)|Xu Xing]] came into possession of the counter slab through a fossil hunter. On comparing his fossil with images of ''Archaeoraptor'' it became evident that it was a composite fake. His note to ''National Geographic'' led to consternation and embarrassment. Lewis Simons investigated the matter on behalf of ''National Geographic''. In October 2000, he reported what he termed:
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