Compression fossil: Difference between revisions

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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 [[distortion]] of the fossil.

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.; Internalinternal [[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"/>

Compression fossils are formed most commonly in [[ecosystem|environment]]s where fine sediment is deposited, such as in [[river delta]]s, [[lagoon]]s, along [[river]]s, and in [[pond]]s. The best rocks in which to find these fossils preserved are [[clay]] and [[shale]], although [[volcanic ash]] may sometimes preserve plant fossils as well.<ref name="Taylor & Taylor 1993"/>

==Slabs==

[[File:Pterodactylus antiquus p and cp.jpg|upright=1.35|thumb|Counter slab (left) and slab (right) of ''[[Pterodactylus]]'']]

{{multiple image

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| 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&dq=fossil+%22Counter+slab%22&pg=PA3 ''New Scientist'' 14 March 1985]</ref>

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:

{{quote|a tale of misguided secrecy and misplaced confidence, of rampant egos clashing, self-aggrandizement, wishful thinking, naïve assumptions, [[human error]], stubbornness, manipulation, backbiting, lying, corruption, and, most of all, abysmal communication.}}

It was eventually determined that ''Archaeoraptor'' had been constructed from parts of an [[Early Cretaceous]] bird ''[[Yanornis martini]]'' and a small dinosaur ''[[Microraptor zhaoianus]]''.<ref>[http://www.ifs.csic.es/sorites/Issue_20/colbourn.htm The Interpretive Mind] {{webarchive|url=https://web.archive.org/web/20100401195602/http://www.ifs.csic.es/sorites/Issue_20/colbourn.htm |date=1 April 2010}}</ref>

In order to increase their profit, fossil hunters and dealers occasionally sell slab and counter slab separately. A reptile fossil also found in Liaoning was described and named ''Sinohydrosaurus'' in 1999 by the [[Beijing Natural History Museum]]. In the same year the [[Institute of Vertebrate Paleontology and Paleoanthropology]] in Beijing described and named ''Hyphalosaurus lingyuanensis'', unaware they were working with the counter slab of the same specimen. ''[[Hyphalosaurus]]'' is now the accepted name.<ref>[http://www.twoguysfossils.com/reptiles.htm Two Guys Fossils] {{webarchive|url=https://archive.today/20120914100749/http://www.twoguysfossils.com/reptiles.htm |date=14 September 2012}}</ref>

==References==

{{Reflist|2|refs=

* Taylor, Thomas N. & Taylor, Edith L. (1993). ''The Biology and Evolution of Fossil Plants''. Englewood Cliffs, NJ: Prentice Hall. ISBN 0-13-651589-4.

<ref name="Arnold 1947">{{cite book | last=Arnold | first=Chester A. | year=1947 | title=An Introduction to Paleobotany | url=https://archive.org/details/in.ernet.dli.2015.270777 | edition=1st | ___location=New York & London | publisher=McGraw-Hill Book Company | pages=[https://archive.org/details/in.ernet.dli.2015.270777/page/n22 14]–40 }}</ref>

[[Category:Fossils]]

[[Category:Paleontology]]

[[Category:Paleobotany]]

<ref name="Stewart 1993">{{cite book | last1=Stewart | first1=Wilson N. | last2=Rothwell | first2=Gar W. |year=1993 | title=Paleobotany and the Evolution of Plants | edition=2nd | ___location=Cambridge | publisher=Cambridge University Press |isbn=0-521-38294-7 | pages=7–22 }}</ref>

*<ref name="Taylor, & Taylor 1993">{{cite book | last1=Taylor | first1=Thomas N. &| last2=Taylor, | first2=Edith L. (| year=1993). ''| title=The Biology and Evolution of Fossil Plants''. | ___location =Englewood Cliffs, NJ: | publisher=Prentice Hall. ISBN| isbn=0-13-651589-4. | pages=7–12 }}</ref>

{{paleo-stub}}

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[[pt:Fóssil de compressão]]

[[Category:FossilsFossilization]]