Pseudofossil
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2008-07-07T13:29:25Z
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[[Image:Dendrites01.jpg|thumb|Manganese dendrites on a limestone bedding plane from [[Solingen]], Germany. Scale in mm.]]
'''Pseudofossils''' are [[inorganic]] objects, markings, or impressions that might be mistaken for [[fossil]]s. Pseudofossils may be misleading, as some types of mineral deposits can mimic lifeforms by forming what appear to be highly detailed or organized structures. One common example is when [[manganese]] oxides [[crystallization|crystallize]] with a characteristic treelike or [[dendrite (crystal)|dendritic]] pattern along a rock fracture. The formation of [[frost]] dendrites on a window is another common example of this crystal growth. [[Concretion|Concretions]] are sometimes thought to be fossils, and occasionally one contains a fossil, but are generally not fossils themselves. [[Chert]] or [[flint]] nodules in [[limestone]] can often take forms that resemble fossils.
[[Pyrite]] disks or spindles are sometimes mistaken for fossils of [[sand dollar]]s or other forms (see [[marcasite]]). Cracks, bumps, [[gas]] bubbles, and such can be difficult to distinguish from true fossils. Specimens which cannot be attributed with certainty to either the fossils or the pseudofossils are treated as [[dubiofossil]]s. Debates about whether specific forms are pseudo or true fossils can be lengthy and difficult. For example, ''[[Eozoön]]'' is a complex laminated form of interlayered [[calcite]] and [[serpentine]] originally found in [[Precambrian]] metamorphosed [[limestone]]s (marbles). It was at first thought to be the remains of a giant fossil protozoan (Dawson, 1865), then being by far the oldest fossil known. Similar structures were subsequently found in metamorphosed limestone blocks ejected during an eruption of Mt. Vesuvius. It was clear that high-temperature physical and chemical processes were responsible for the formation of ''Eozoön'' in the carbonate rock (O'Brien, 1970). The debate over the interpretation of ''Eozoon'' was a significant episode in the history of paleontology (Adelman, 2007).
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Image:Concretion01.jpg|Concretion with calcite-filled septarian cracks. Scale in mm.
Image:Eozoon01.jpg|''Eozoön canadense'' from the [[Precambrian]] of Canada, a metamorphic rock made of interlayered [[calcite]] and [[serpentine]]. A well-known pseudofossil (Adelman, 2007). Scale in mm.
Image:ShatterCones.jpg|[[Shatter cones]] produced by compression of limestone. Sometimes mistaken for fossils, thus becoming examples of pseudofossils. Scale in mm.
Image:Markasit hg.jpg|A marcasite (pyrite) crystal form resembling a sand dollar.
Image:Pseudocoprolite.jpg|A [[Miocene]] pseudocoprolite from Washington state. This is one of the most common pseudofossils because it so closely resembles a [[coprolite]]. Scale in mm. See Spencer (1993).
</gallery>
==References==
* {{cite journal|last=Adelman|first=J.|coauthors=|year=2007|title=''Eozoön'': debunking the dawn animal|journal=Endeavor|issn=0160-9327|volume=31|issue=3|pages=94-98}}
* {{cite journal|last=Dawson|first=J. W.|coauthors=|year=1865|title=On the structure of certain organic remains in the Laurentian limestones of Canada|journal=Quart. J. Geol. Soc.|issn=|volume=21|issue=|pages=51–59}}
* {{cite journal|last=O'Brien|first=C. F.|coauthors=|year=1970|title=''Eozoön canadense'' "The dawn animal of Canada"|journal=Isis|issn=00211753|volume=61|issue=|pages=206-223}}
* {{cite journal|last=Spencer|first=P. K.|coauthors=|year=1993|title=The "coprolites" that aren't: the straight poop on specimens from the Miocene of southwestern Washington State|journal=Ichnos|issn=1042-0940|volume=2|issue=|pages=1-6}}
[[Category:Paleontology]]
{{Commonscat|Pseudofossils}}
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