Editing Trace fossil

{{short description|Geological record of biological activity}}
{{about|a type of fossil|Dinosaur Footprints park in Massachusetts|Dinosaur Footprints}}
[[Image:Cheirotherium prints possibly Ticinosuchus.JPG|thumb|''[[Chirotherium]]'' footprints in a [[Triassic]] sandstone]]
{{wikt | ichnofossil}}
{{Paleontology}}
[[Image:Protichnites.jpg|thumb|upright|The trackway ''[[Protichnites]]'' from the [[Cambrian]], [[Blackberry Hill]], central [[Wisconsin]]]]

A '''trace fossil''', also called an '''ichnofossil''' ({{IPAc-en|ˈ|ɪ|k|n|oʊ|ˌ|f|ɒ|s|ᵻ|l}}; {{etymology|grc|''{{wikt-lang|grc|ἴχνος}}'' ({{grc-transl|ἴχνος}})|trace, track}}), is a [[fossil]] record of [[earliest known life forms|biological activity]] by [[lifeform]]s, but not the preserved remains of the [[organism]] itself.<ref>{{Cite web |title=GEOL 331/BSCI 333 Ichnology: The Study of Trace Fossils |url=https://www.geol.umd.edu/~tholtz/G331/lectures/331ichno.html |access-date=2024-10-25 |website=www.geol.umd.edu}}</ref> Trace fossils contrast with body fossils, which are the fossilized remains of parts of organisms' bodies, usually altered by later chemical activity or by [[Mineralization (geology)|mineralization]]. The study of such trace fossils is '''ichnology''' - the work of '''ichnologists'''.<ref>{{Cite journal |last1=Pineda-Salgado |first1=Gabriela |last2=Quiroz-Barroso |first2=Sara A. |last3=Pineda-Salgado |first3=Gabriela |last4=Quiroz-Barroso |first4=Sara A. |date=2018 |title=Ichnology: modern and fossil evidence of biological activity |url=https://www.scielo.org.mx/scielo.php?pid=S1405-33222018000200001&script=sci_arttext |journal=Boletín de la Sociedad Geológica Mexicana |language=en |volume=70 |issue=2 |pages=0 |doi=10.18268/bsgm2018v70n2p1 |issn=1405-3322|doi-access=free }}</ref>

Trace fossils may consist of physical impressions made on or in the [[Substrate (marine biology)|substrate]] by an organism.<ref>{{Cite web |date=2024-02-08 |title=8.3: Trace Fossils- Studies in Scurrying, Scraping, and Slithering |url=https://geo.libretexts.org/Bookshelves/Geology/Introduction_to_Historical_Geology_(Johnson_et_al.)/08:_Taphonomy_-_The_Science_of_Death_and_Decay/8.03:_Trace_Fossils-_Studies_in_Scurrying_Scraping_and_Slithering |access-date=2024-10-25 |website=Geosciences LibreTexts |language=en}}</ref> For example, [[burrow fossil|burrow]]s, borings ([[bioerosion]]), [[urolite]]s (erosion caused by evacuation of liquid wastes), [[Ichnite|footprints]], feeding marks, and root cavities may all be trace fossils.

The term in its broadest sense also includes the remains of other organic material produced by an organism; for example [[coprolite]]s (fossilized droppings) or chemical markers (sedimentological structures produced by biological means; for example, the formation of [[stromatolites]]). However, most [[sedimentary structures]] (for example those produced by empty shells rolling along the sea floor) are not produced through the behaviour of an organism and thus are not considered trace fossils.

The study of traces – ichnology – divides into ''paleoichnology'', or the study of trace fossils, and ''neoichnology'', the study of modern traces. Ichnological science offers many challenges, as most traces reflect the behaviour – not the biological affinity – of their makers. Accordingly, researchers classify trace fossils into [[form genera]] based on their [[Morphology (biology)|appearance]] and on the implied behaviour, or [[ethology]], of their makers.

==Occurrence==
[[Image:MammothFootImpressions25.jpg|thumb|right|Cross-section of [[mammoth]] footprints at [[The Mammoth Site]], [[Hot Springs, South Dakota]]]]
Traces are better known in their fossilized form than in modern sediments.<ref name=Seilacher1967/> This makes it difficult to interpret some fossils by comparing them with modern traces, even though they may be extant or even common.<ref name=Seilacher1967/> The main difficulties in accessing extant burrows stem from finding them in consolidated sediment, and being able to access those formed in deeper water.

[[File:Coprolite with Distinct Vertebrate Bite Marks.jpg|thumb|This [[coprolite]] shows distinct top and bottom jaw bite marks, possibly from a prehistoric [[gar]] fish. Discovery location: [[South Carolina]], [[United States|US]]; age: [[Miocene]]; dimensions: {{convert|144.6|x|63.41|mm|in|abbr=on}}; weight: {{convert|558|g|lboz|abbr=on}}]]

Trace fossils are best preserved in sandstones;<ref name=Seilacher1967/> the grain size and depositional facies both contributing to the better preservation. They may also be found in shales and limestones.<ref name=Seilacher1967/>

==Classification==
{{main|Trace fossil classification}}
Trace fossils are generally difficult or impossible to assign to a specific maker. Only in very rare occasions are the makers found in association with their tracks. Further, entirely different organisms may produce identical tracks. Therefore, conventional taxonomy is not applicable, and a comprehensive form of taxonomy has been erected. At the highest level of the classification, five behavioral modes are recognized:<ref name=Seilacher1967>{{cite journal
 | author = Seilacher, D.
 | year = 1967
 | title = Bathymetry of trace fossils
 | journal = Marine Geology
 | volume = 5
 | issue = 5–6
 | doi = 10.1016/0025-3227(67)90051-5
 | pages = 413–428
| bibcode = 1967MGeol...5..413S
 }}</ref>
* '''Domichnia''', dwelling structures reflecting the life position of the organism that created it.
* '''Fodinichnia''', three-dimensional structures left by animals which eat their way through sediment, such as deposit feeders;
* '''Pascichnia''', feeding traces left by grazers on the surface of a soft sediment or a mineral substrate;
* '''Cubichnia''', resting traces, in the form of an impression left by an organism on a soft sediment;
* '''Repichnia''', surface traces of creeping and crawling.

Fossils are further classified into form genera, a few of which are even subdivided to a "species" level. Classification is based on shape, form, and implied behavioural mode.

To keep body and trace fossils nomenclatorially separate, ''ichnospecies'' are erected for trace fossils. [[Ichnotaxa]] are classified somewhat differently in [[zoological nomenclature]] than taxa based on body fossils (see [[trace fossil classification]] for more information). Examples include:
*Late [[Cambrian]] trace fossils from intertidal settings include ''[[Protichnites]]'' and ''[[Climactichnites]]'', amongst others
*[[Mesozoic]] dinosaur footprints including ichnogenera such as ''[[Grallator]]'', ''[[Atreipus]]'', and ''[[Anomoepus]]''
*[[Triassic]] to [[Holocene|Recent]] termite mounds, which can encompass several square kilometers of sediment

== Information provided by ichnofossils ==
[[Image:Mesolimulus walchi trackway and fossil.jpg|thumb|left|''[[Mesolimulus|Mesolimulus walchi]]'' fossil and track, a rare example of tracks and the creature that made them fossilized together]]
Trace fossils are important paleoecological and paleoenvironmental indicators, because they are preserved [[in situ]], or in the life position of the organism that made them.<ref>{{Cite book|url=https://raregeologybooks.files.wordpress.com/2015/03/principles-of-sedimentology-and-stratigraphy-by-sam-jr-boggs.pdf|title=Principles of Sedimentology and Stratigraphy|last=Boggs, Jr.|first=Sam|publisher=Pearson Education|year=2006|isbn=978-0-13-154728-5|edition=4th|location=Upper Saddle River, NJ|pages=102–110|access-date=2017-02-01|archive-url=https://web.archive.org/web/20160331122234/https://raregeologybooks.files.wordpress.com/2015/03/principles-of-sedimentology-and-stratigraphy-by-sam-jr-boggs.pdf|archive-date=2016-03-31}}</ref> Because identical fossils can be created by a range of different organisms, trace fossils can only reliably inform us of two things: the consistency of the sediment at the time of its deposition, and the energy level of the [[Sedimentary depositional environment|depositional environment]].<ref name=Woolfe1990/> Attempts to deduce such traits as whether a deposit is marine or non-marine have been made, but shown to be unreliable.<ref name=Woolfe1990>{{cite journal
 | author = Woolfe, K.J.
 | year = 1990
 | title = Trace fossils as paleoenvironmental indicators in the Taylor Group (Devonian) of Antarctica
 | journal = Palaeogeography, Palaeoclimatology, Palaeoecology
 | volume = 80
 | pages = 301–310
 | doi = 10.1016/0031-0182(90)90139-X
 | issue = 3–4
| bibcode = 1990PPP....80..301W
 }}</ref>

=== Paleoecology ===
Trace fossils provide us with indirect evidence of [[prehistoric life|life in the past]], such as the footprints, tracks, burrows, borings, and feces left behind by animals, rather than the preserved remains of the body of the actual animal itself. Unlike most other fossils, which are produced only after the death of the organism concerned, trace fossils provide us with a record of the activity of an organism during its lifetime. Unlike body fossils, which can be transported far away from where an individual organism lived, trace fossils record the type of environment an animal actually inhabited and thus can provide a more accurate palaeoecological sample than body fossils.<ref>{{Cite journal |last=Belvedere |first=Matteo |last2=Jalil |first2=Nour-Eddine |last3=Breda |first3=Anna |last4=Gattolin |first4=Giovanni |last5=Bourget |first5=Hélène |last6=Khaldoune |first6=Fatima |last7=Dyke |first7=Gareth J. |date=August 2013 |title=Vertebrate footprints from the Kem Kem beds (Morocco): A novel ichnological approach to faunal reconstruction |url=https://www.sciencedirect.com/science/article/pii/S0031018213002137 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |language=en |volume=383-384 |pages=52–58 |doi=10.1016/j.palaeo.2013.04.026 |access-date=5 November 2024 |via=Elsevier Science Direct|url-access=subscription }}</ref>

Trace fossils are formed by organisms performing the functions of their everyday life, such as walking, crawling, burrowing, boring, or feeding. [[Tetrapod]] footprints, [[worm]] trails and the burrows made by [[clam]]s and [[arthropods]] are all trace fossils.

Perhaps the most spectacular trace fossils are the huge, three-toed footprints produced by [[dinosaur]]s and related [[archosaur]]s. These imprints give scientists clues as to how these animals lived. Although the skeletons of dinosaurs can be reconstructed, only their [[fossilized]] footprints can determine exactly how they stood and walked. Such tracks can tell much about the gait of the animal which made them, what its stride was, and whether the front limbs touched the ground or not.

However, most trace fossils are rather less conspicuous, such as the trails made by [[segmented worm]]s or [[nematode]]s. Some of these [[worm]] castings are the only fossil record we have of these soft-bodied creatures.{{Citation needed|date=December 2021}}


=== Paleoenvironment ===
[[Image:Eubrontes01.JPG|thumb|upright|''[[Eubrontes]]'', a [[dinosaur]] footprint in the Lower [[Jurassic]] [[Moenave Formation]] at the [[St. George Dinosaur Discovery Site]] at Johnson Farm, southwestern [[Utah]]]]
Fossil footprints made by tetrapod [[vertebrate]]s are difficult to identify to a particular species of animal, but they can provide valuable information such as the speed, weight, and behavior of the organism that made them. Such trace fossils are formed when [[amphibian]]s, [[reptile]]s, [[mammal]]s, or [[bird]]s walked across soft (probably wet) mud or sand which later hardened sufficiently to retain the impressions before the next layer of sediment was deposited. Some fossils can even provide details of how wet the sand was when they were being produced, and hence allow estimation of paleo-wind directions.<ref name=Trewin1995>{{cite journal
 | author = Trewin, N.H.
 |author2=McNamara, K.J.
  | year = 1995
 | title = Arthropods invade the land: trace fossils and palaeoenvironments of the Tumblagooda Sandstone (? late Silurian) of Kalbarri, Western Australia
 | journal = Transactions of the Royal Society of Edinburgh: Earth Sciences
 | volume = 85
 |issue=3
  | pages = 177–210
 | doi=10.1017/s026359330000359x
|s2cid=129036273
 }}</ref>

Assemblages of trace fossils occur at certain water depths,<ref name=Seilacher1967 /> and can also reflect the salinity and turbidity of the water column.

=== Stratigraphic correlation ===
Some trace fossils can be used as local [[index fossil]]s, to date the rocks in which they are found, such as the burrow ''[[Arenicolites]] franconicus'' which occurs only in a {{convert|4|cm|in|frac=2|abbr=on}} layer of the [[Triassic]] [[Muschelkalk]] epoch, throughout wide areas in southern [[Germany]].<ref name=Schlirf2006>{{cite journal
 | author = Schlirf, M.
 | year = 2006
 | title = ''Trusheimichnus'' New Ichnogenus From the Middle Triassic of the Germanic Basin, Southern Germany
 | journal = Ichnos
 | volume = 13
 | issue = 4
 | pages = 249–254
 | doi = 10.1080/10420940600843690
| s2cid = 129437483
 }}</ref>

The base of the [[Cambrian]] period is defined by the first appearance of the trace fossil ''[[Treptichnus pedum]]''.<ref>{{Cite journal
  | last1 = Gehling
  | first1 = James
  | last2 = Jensen
  | first2 = Sören
  | last3 = Droser
  | first3 = Mary
  | last4 = Myrow
  | first4 = Paul
  | last5 = Narbonne
  | first5 = Guy
  | title = Burrowing below the basal Cambrian GSSP, Fortune Head, Newfoundland
  | journal = Geological Magazine
  | volume = 138
  | issue = 2
  | pages = 213–218
  |date=March 2001
  | doi = 10.1017/S001675680100509X
| bibcode = 2001GeoM..138..213G
  | s2cid = 131211543
 }}
</ref>

Trace fossils have a further utility, as many appear before the organism thought to create them, extending their stratigraphic range.<ref name=Seilacher1994>e.g. {{cite journal
 | author = Seilacher, A.
 | year = 1994
 | title = How valid is ''Cruziana'' Stratigraphy?
 | journal = International Journal of Earth Sciences
 | volume = 83
 | issue = 4
 | pages = 752–758
 | doi=10.1007/BF00251073
 | bibcode=1994GeoRu..83..752S
| s2cid = 129504434
 }}</ref>

== Ichnofacies ==
{{main|Ichnofacies}}
[[Ichnofacies]] are assemblages of individual trace fossils that occur repeatedly in time and space.<ref name=":0">{{Cite book|url=https://raregeologybooks.files.wordpress.com/2015/03/principles-of-sedimentology-and-stratigraphy-by-sam-jr-boggs.pdf|title=Principles of Sedimentology and Stratigraphy|last=Boggs, Jr.|first=Sam|publisher=Pearson Education, Inc.|year=2006|isbn=978-0-13-154728-5|edition=4th|location=Upper Saddle River, NJ|pages=102–110|access-date=2017-02-01|archive-url=https://web.archive.org/web/20160331122234/https://raregeologybooks.files.wordpress.com/2015/03/principles-of-sedimentology-and-stratigraphy-by-sam-jr-boggs.pdf|archive-date=2016-03-31}}</ref> Palaeontologist [[Adolf Seilacher]] pioneered the concept of ichnofacies, whereby geologists infer the state of a sedimentary system at its time of deposition by noting the fossils in association with one another.<ref name="Seilacher1967" /> The principal ichnofacies recognized in the literature are ''[[Skolithos]]'', ''[[Cruziana]]'', ''[[Zoophycos]]'', ''[[Nereites]], Glossifungites, [[Scoyenia]], [[Trypanites]], [[Teredolites]],'' and ''[[Psilonichnus|Psilonichus]]''.<ref name=":0" /><ref name=":1">{{Cite book|title=Facies Models 4|last1=MacEachern|first1=James|last2=Pemberon|first2=S. George|last3=Gingras|first3=Murray K.|last4=Bann|first4=Kerrie L.|year=2010|isbn=978-1-897095-50-8|editor-last=James|editor-first=Noel|pages=19–58|chapter=Ichnology and Facies Models|publisher=Geological Association of Canada |editor-last2=Dalrymple|editor-first2=Robert W.}}</ref> These assemblages are not random. In fact, the assortment of fossils preserved are primarily constrained by the environmental conditions in which the trace-making organisms dwelt.<ref name=":1" /> Water depth, [[salinity]], hardness of the substrate, dissolved oxygen, and many other environmental conditions control which organisms can inhabit particular areas.<ref name=":0" /> Therefore, by documenting and researching changes in ichnofacies, scientists can interpret changes in environment.<ref name=":1" /> For example, ichnological studies have been utilized across mass extinction boundaries, such as the [[Cretaceous–Paleogene extinction event|Cretaceous–Paleogene mass extinction]], to aid in understanding environmental factors involved in mass extinction events.<ref>{{Cite journal|last1=Buatois|first1=Luis A.|last2=Angulo|first2=Solange|last3=Mangano|first3=María G.|date=2013-04-01|title=Onshore expansion of benthic communities after the Late Devonian mass extinction|journal=Lethaia|language=en|volume=46|issue=2|pages=251–261|doi=10.1111/let.12001|issn=1502-3931}}</ref><ref>{{Cite book|title=Trace Fossils: Concepts, Problems, Prospects|last1=Marrow|first1=Jared R.|last2=Hasiotis|first2=Stephen T.|publisher=Elsevier Science|year=2007|isbn=978-0-444-52949-7|editor-last=Miller III|editor-first=William|pages=575–598|chapter=Endobenthic Response through Mass-Extinction Episodes: Predictive Models and Observed Patterns}}</ref>

== Inherent bias ==
[[File:Hadrosaur tracks.png|thumb|upright=1.4|Diagram showing how dinosaur footprints are preserved in different deposits]] 
Most trace fossils are known from marine deposits.<ref>{{cite web |last=Saether |first=Kristian |author2=Christopher Clowes |title=Trace Fossils |url=http://www.peripatus.gen.nz/paleontology/TraFos.html |access-date=2009-06-19 |archive-url=https://web.archive.org/web/20090416063931/http://www.peripatus.gen.nz/paleontology/trafos.html |archive-date=2009-04-16 }}</ref> Essentially, there are two types of traces, either exogenic ones, which are made on the surface of the sediment (such as tracks) or endogenic ones, which are made within the layers of sediment (such as burrows).

Surface trails on sediment in shallow marine environments stand less chance of fossilization because they are subjected to wave and current action. Conditions in quiet, deep-water environments tend to be more favorable for preserving fine trace structures.

Most trace fossils are usually readily identified by reference to similar phenomena in modern environments. However, the structures made by organisms in recent sediment have only been studied in a limited range of environments, mostly in coastal areas, including [[tidal flat]]s.{{Citation needed|date=January 2008}}

== Evolution ==
[[Image:Climactichnites - Todd Gass.jpg|thumb|''[[Climactichnites]] wilsoni'', probably trails from a slug-like animal, from the [[Cambrian]], [[Blackberry Hill]], central [[Wisconsin]]. The ruler in the background is {{convert|45|cm|in|abbr=on}} long.]]
The earliest complex trace fossils, not including microbial traces such as [[stromatolites]], date to {{Ma|2000|1800}}. This is far too early for them to have an animal origin, and they are thought to have been formed by [[amoeba]]e.<ref name='Bengtson2009'>{{cite journal
 | doi = 10.1126/science.1168794
 |date=January 2009
 |author1=Bengtson, S |author2=Rasmussen, B | title = Paleontology. New and ancient trace makers
 | volume = 323
 | issue = 5912
 | pages = 346–7
 | pmid = 19150833
 | journal = Science |hdl=20.500.11937/24668
 |s2cid=1922434
 | hdl-access = free
 }}</ref>
Putative "burrows" dating as far back as {{Ma|1100|million years}} may have been made by animals which fed on the undersides of microbial mats, which would have shielded them from a chemically unpleasant ocean;<ref name=Seilacher1998>{{cite journal
 | author = Seilacher, A.
 | author-link = Adolf Seilacher |author2=Bose, P.K. |author3=Pflüger, F.
 | date = 1998-10-02
 | title = Triploblastic Animals More Than 1 Billion Years Ago: Trace Fossil Evidence from India
 | journal = Science
 | volume = 282
 | issue = 5386
 | pages = 80–83
 | doi = 10.1126/science.282.5386.80
 | pmid = 9756480
 |bibcode = 1998Sci...282...80S }}</ref> however their uneven width and tapering ends make a biological origin so difficult to defend<ref name=Budd2000>{{cite journal
 | author = Budd, G.E.
 |author2=Jensen, S.
 | year = 2000
 | title = A critical reappraisal of the fossil record of the bilaterian phyla
 | journal = Biological Reviews
 | volume = 75
 | issue = 2
 | pages = 253–295
 | doi = 10.1111/j.1469-185X.1999.tb00046.x
 | url = http://www.journals.cambridge.org/abstract_S000632310000548X
 | format = abstract
| pmid=10881389|s2cid=39772232
 | url-access = subscription
 }}</ref> that even the original author no longer believes they are authentic.<ref>{{cite journal
 | doi = 10.1126/science.1166220
 | title = PALEONTOLOGY: Reading Behavior from the Rocks
 | year = 2008
 | author = Jensen, S.
 | journal = Science
 | volume = 322
 | pages = 1051–1052
 | issue = 5904 | s2cid = 129734373
 }}</ref>

The first evidence of burrowing which is widely accepted dates to the [[Ediacaran]] (Vendian) period, around {{Ma|560}}.<ref>{{Cite web|url=https://www.palaeontologyonline.com/articles/2017/fossil-focus-ediacaran-biota/|title=Fossil Focus: The Ediacaran Biota|last=Frances S. Dunn and Alex G. Liu|date=2017|website=Paleontology Online}}</ref> During this period the traces and burrows basically are horizontal on or just below the seafloor surface. Such traces must have been made by motile organisms with heads, which would probably have been [[bilateria|bilateran]] [[animal]]s.<ref>{{cite book
 | author = Fedonkin, M.A.
 | year = 1992
 | title = Vendian faunas and the early evolution of Metazoa
 | journal = In Lipps, J., and Signor, P. W., Eds., Origin and Early Evolution of the Metazoa: New York, Plenum Press.
 | pages = 87–129
 | url = https://books.google.com/books?id=gUQMKiJOj64C&pg=PP1
 | isbn = 978-0-306-44067-0
 | publisher = Springer
 | access-date = 2007-03-08
 }}</ref> The traces observed imply simple behaviour, and point to organisms feeding above the surface and burrowing for protection from predators.<ref name=Dzik2007>
{{The Rise and Fall of the Ediacaran Biota|author=Dzik, J |chapter=The Verdun Syndrome: simultaneous origin of protective armour and infaunal shelters at the Precambrian–Cambrian transition |pages=405-414 |doi=10.1144/SP286.30}}</ref> Contrary to widely circulated opinion that Ediacaran burrows are only horizontal the vertical burrows ''[[Skolithos]]'' are also known.<ref name=Fedonkin_1985>M. A. Fedonkin (1985). "Paleoichnology of Vendian Metazoa". In Sokolov, B. S. and Iwanowski, A. B., eds., "Vendian System: Historical–Geological and Paleontological Foundation, Vol. 1: Paleontology". Moscow: Nauka, pp. 112–116. (in Russian)</ref> The producers of burrows ''[[Skolithos]] declinatus'' from the Vendian (Ediacaran) beds in [[Russia]] with date {{Ma|555.3}} have not been identified; they might have been filter feeders subsisting on the nutrients from the suspension. The density of these burrows is up to 245 burrows/dm<sup>2</sup>.<ref>{{cite journal|last=Grazhdankin|first=D. V.|author2=A. Yu. Ivantsov |year=1996|title=Reconstruction of biotopes of ancient Metazoa of the Late Vendian White Sea Biota|journal=Paleontological Journal|volume=30|pages=676–680}}</ref> Some Ediacaran trace fossils have been found directly associated with body fossils. ''[[Yorgia]]'' and ''[[Dickinsonia]]'' are often found at the end of long pathways of trace fossils matching their shape.<ref name=Ivantsov2002>{{cite journal
 |author      = Ivantsov, A.Y.
 |author2     = Malakhovskaya, Y.E.
 |year        = 2002
 |title       = Giant Traces of Vendian Animals
 |journal     = Doklady Earth Sciences
 |volume      = 385
 |issue       = 6
 |pages       = 618–622
 |issn        = 1028-334X
 |url         = http://vend.paleo.ru/pub/Ivantsov_et_Malakhovskaya_2002-e.pdf
 |access-date  = 2007-05-10
 |archive-url  = https://web.archive.org/web/20070704183947/http://vend.paleo.ru/pub/Ivantsov_et_Malakhovskaya_2002-e.pdf
 |archive-date = 2007-07-04
}}</ref> The feeding was performed in a mechanical way, supposedly the ventral side of body these organisms was covered with [[cilia]].<ref name=Oslo_2008>A. Yu. Ivantsov. (2008). [http://www.cprm.gov.br/33IGC/1323085.html "Feeding traces of the Ediacaran animals"]. HPF-17 Trace fossils ? ichnological concepts and methods. International Geological Congress - Oslo 2008.</ref> The potential [[mollusc]] related ''[[Kimberella]]'' is associated with scratch marks, perhaps formed by a [[radula]],<ref name=Fedonkin2007>{{The Rise and Fall of the Ediacaran Biota |chapter=New data on ''Kimberella'', the Vendian mollusc-like organism (White sea region, Russia): palaeoecological and evolutionary implications |author=Fedonkin, M.A. |author2=Simonetta, A |author3=Ivantsov, A.Y. |pages=157–179 |doi=10.1144/SP286.12}}</ref> further traces from {{Ma|555}} appear to imply active crawling or burrowing activity.<ref name=Martin2000>According to {{cite journal
 | author = Martin, M.W.
 |author2=Grazhdankin, D.V. |author3=Bowring, S.A. |author4=Evans, D.A.D. |author5=Fedonkin, M.A. |author6= Kirschvink, J.L. 
 | date = 2000-05-05
 | title = Age of Neoproterozoic Bilatarian Body and Trace Fossils, White Sea, Russia: Implications for Metazoan Evolution
 | journal = Science
 | volume = 288
 | issue = 5467
 | pages = 841–5
 | doi = 10.1126/science.288.5467.841
 | pmid = 10797002
 |bibcode = 2000Sci...288..841M |s2cid=1019572 }}</ref>

As the [[Cambrian]] got underway, new forms of trace fossil appeared, including vertical burrows (e.g. ''[[Diplocraterion]]'') and traces normally attributed to [[arthropod]]s.<ref>Such as ''[[Cruziana]]'' and ''[[Rusophycus]]''. Details of Cruziana's formation are reported by {{cite journal
 | author = Goldring, R.
 | date =  January 1, 1985 | title = The formation of the trace fossil Cruziana
 | journal = Geological Magazine
 | volume = 122
 | issue = 1
 | pages = 65–72
 | url = http://geolmag.geoscienceworld.org/cgi/content/abstract/122/1/65
 | access-date = 2007-09-09
 | doi = 10.1017/S0016756800034099
 | bibcode = 1985GeoM..122...65G
 | s2cid = 130340569 | url-access = subscription
 }}</ref> These represent a "widening of the behavioural repertoire",<ref name=ConwayMorris1989>{{cite journal
 | author = Conway Morris, S.
 | year = 1989
 | title = Burgess Shale Faunas and the Cambrian Explosion
 | journal = Science
 | volume = 246
 | issue = 4928
 | pages = 339–46
 | doi = 10.1126/science.246.4928.339
 | pmid = 17747916
 | bibcode=1989Sci...246..339C
| s2cid = 10491968
 }}</ref> both in terms of abundance and complexity.<ref>{{cite journal
| title=The Proterozoic and Earliest Cambrian Trace Fossil Record; Patterns, Problems and Perspectives
| author=Jensen, S.
| journal=Integrative and Comparative Biology
| volume=43
| year=2003
| pages=219–228
| doi = 10.1093/icb/43.1.219
| issue=1
 | pmid=21680425| doi-access=free
}}</ref>

Trace fossils are a particularly significant source of data from this period because they represent a data source that is not directly connected to the presence of easily fossilized hard parts, which are rare during the Cambrian. Whilst exact assignment of trace fossils to their makers is difficult, the trace fossil record seems to indicate that at the very least, large, bottom-dwelling, [[Symmetry (biology)#Bilateral symmetry|bilaterally symmetrical]] organisms were rapidly diversifying during the early [[Cambrian]].<ref>Although some [[cnidaria]]ns are effective burrowers, e.g. {{cite journal
 |author       = Weightman, J.O.
 |author2      = Arsenault, D.J.
 |year         = 2002
 |title        = Predator classification by the sea pen ''Ptilosarcus gurneyi'' (Cnidaria): role of waterborne chemical cues and physical contact with predatory sea stars
 |volume       = 80
 |issue        = 1
 |pages        = 185–190
 |doi          = 10.1139/z01-211
 |url          = http://pubs.nrc-cnrc.gc.ca/rp/rppdf/z01-211.pdf
 |access-date   = 2007-04-21
 |journal      = Canadian Journal of Zoology
 |archive-url  = https://web.archive.org/web/20070927211505/http://pubs.nrc-cnrc.gc.ca/rp/rppdf/z01-211.pdf
 |archive-date = 2007-09-27
 }} most Cambrian trace fossils have been assigned to bilaterian animals.</ref>

Further, less rapid{{Verify source|date=April 2008}} diversification occurred since,{{Verify source|date=April 2008}} and many traces have been converged upon independently by unrelated groups of organisms.<ref name=Seilacher1967/>

Trace fossils also provide our earliest evidence of animal life on land.<ref>{{Cite news|url=https://phys.org/news/2017-06-life-terra-firma-began-invasion.html|title=Life on terra firma began with an invasion|work=Phys.org News|access-date=2017-06-04}}</ref> Evidence of the first animals that appear to have been fully terrestrial dates to the Cambro-Ordovician and is in the form of trackways.<ref name=MacNaughton2002>{{cite journal
 | author = MacNaughton, R.B.
 |author2=Cole, J.M. |author3=Dalrymple, R.W. |author4=Braddy, S.J. |author5=Briggs, D.E.G. |author6= Lukie, T.D. 
 | year = 2002
 | title = First steps on land: Arthropod trackways in Cambrian-Ordovician eolian sandstone, southeastern Ontario, Canada
 | journal = Geology
 | volume = 30
 | issue = 5
 | pages = 391–394
 | doi = 10.1130/0091-7613(2002)030<0391:FSOLAT>2.0.CO;2
 | issn = 0091-7613
 | bibcode=2002Geo....30..391M
|s2cid=130821454 }}</ref> Trackways from the Ordovician [[Tumblagooda sandstone]] allow the behaviour of other terrestrial organisms to be determined.<ref name=Trewin1995/> The trackway ''[[Protichnites]]'' represents traces from an amphibious or terrestrial arthropod going back to the Cambrian.<ref name="ColletteEtAl2012">{{cite journal |last1=Collette |first1=J.H. |last2=Gass |first2=K.C. |last3=Hagadorn |first3=J.W. |title=Protichnites eremita unshelled? Experimental model-based neoichnology and new evidence for a euthycarcinoid affinity for this ichnospecies |journal=Journal of Paleontology |year=2012 |volume=86 |issue=3 |pages=442–454 |doi=10.1666/11-056.1|bibcode=2012JPal...86..442C |s2cid=129234373 }}</ref>

== Common ichnogenera ==
[[Image:Petroxestes pera Ordovician Ohio.jpg|thumb|''[[Petroxestes]]'' borings in a hardground from the Upper [[Ordovician]] of southern [[Ohio]]]]
[[Image:RusophycusOrdovician.jpg|thumb|right|''[[Rusophycus]]'' trace fossil from the [[Ordovician]] of southern [[Ohio]]. Scale bar is 10 mm.]]
[[Image:Skolithos.jpg|thumb|''[[Skolithos]]'' trace fossil. Scale bar is 10 mm.]]
[[Image:ThalassinoidesIsrael.JPG|thumb|''[[Thalassinoides]]'', burrows produced by crustaceans, from the Middle [[Jurassic]], [[Makhtesh]] Qatan, southern [[Israel]]]]
[[Image:Trypanites01.jpg|thumb|''[[Trypanites]]'' borings in an Upper [[Ordovician]] [[hardground]] from northern Kentucky. The borings are filled with diagenetic [[Dolomite (mineral)|dolomite]] (yellowish). The boring on the far right cuts through a shell in the matrix.]]
[[Image:Trace fossils in Uruguay.JPG|thumbnail|''Ophiomorpha'' and ''Thalassinoides'' trace fossils produced by crustaceans found at Camacho formation from the Late [[Miocene]] in [[Colonia Department]], [[Uruguay]]]]
*''[[Anoigmaichnus]]'' is a [[bioclaustration]]. It occurs in the Ordovician bryozoans. Apertures of ''Anoigmaichnus'' are elevated above their hosts' growth surfaces, forming short chimney-like structures.
* ''[[Arachnostega]]'' is the name given to the irregular, branching burrows in the sediment fill of shells. They are visible on the surface of steinkerns. Their traces are known from the [[Cambrian]] period onwards.<ref name='VinnWilsonZatonToom2014'>{{cite journal
 | title = The trace fossil Arachnostega in the Ordovician of Estonia (Baltica)
 | year = 2014
 | author = Vinn, O.
 | author2 = Wilson, M.A.
 | author3 = Zatoń, M.
 | author4= Toom, U.
 | journal = Palaeontologia Electronica
 | volume = 17.3.40A
 | pages = 1–9
 | url = http://palaeo-electronica.org/content/2014/960-arachnostega-in-the-ordovician
 | access-date = 2014-06-10}}</ref>
* ''[[Asteriacites]]'' is the name given to the five-rayed fossils found in rocks and they record the resting place of [[starfish]] on the sea floor. ''Asteriacites'' are found in European and American rocks, from the [[Ordovician]] period onwards, and are numerous in rocks from the [[Jurassic]] period of [[Germany]].
* ''[[Burrinjuckia]]'' is a bioclaustration. ''Burrinjuckia ''includes outgrowths of the [[brachiopod]]'s secondary shell with a hollow interior in the mantle cavity of a brachiopod. 
* ''[[Chondrites (genus)|Chondrites]]'' (not to be confused with stony meteorites of the same name) are small branching burrows of the same diameter, which superficially resemble the roots of a plant. The most likely candidate for having constructed these burrows is a [[nematode]] (roundworm). ''Chondrites'' are found in marine sediments from the [[Cambrian]] period of the [[Paleozoic]] onwards. They are especially common in sediments which were deposited in reduced-oxygen environments.
* ''[[Climactichnites]]'' is the name given to surface trails and burrows that consist of a series of chevron-shaped raised cross bars that are usually flanked on either side by a parallel ridge. They somewhat resemble tire tracks, and are larger (typically about {{convert|4|in|cm|order=flip|abbr=on|0|disp=or}} wide) than most of the other trace fossils made by [[invertebrates]]. The trails were produced on sandy tidal flats during [[Cambrian]] time. While the identity of the animal is still conjectural, it may have been a large [[slug]]-like animal – its trails produced as it crawled over and processed the wet sand to obtain food.<ref>{{cite journal|last=Getty|first=Patrick|author2=James Hagadorn |title=Palaeobiology of the ''Climactichnites'' trailmaker|journal=Palaeontology|year=2009|volume=52|issue=4|pages=758–778|doi=10.1111/j.1475-4983.2009.00875.x|bibcode=2009Palgy..52..753G |citeseerx=10.1.1.597.192|s2cid=129182104 }}</ref><ref>{{cite journal|last=Getty|first=Patrick|author2=James Hagadorn |title=Reinterpretation of ''Climactichnites'' Logan 1860 to Include Subsurface Burrows, and Erection of ''Musculopodus'' for Resting Traces of the Trailmaker|journal=Journal of Paleontology|year=2008|volume=82|issue=6|pages=1161–1172|doi=10.1666/08-004.1|bibcode=2008JPal...82.1161G |s2cid=129732925}}</ref>
* ''[[Cruziana]]'' are excavation trace marks made on the sea floor which have a two-lobed structure with a central groove. The lobes are covered with scratch marks made by the legs of the excavating organism, usually a [[trilobite]] or allied arthropod. ''Cruziana'' are most common in marine sediments formed during the [[Paleozoic]] era, particularly in rocks from the [[Cambrian]] and [[Ordovician]] periods. Over 30 ichnospecies of ''Cruziana'' have been identified. See also [[Isopodichnus]].
* ''[[Entobia]]'' is a boring produced by endolithic clionaid [[sponges]] consisting of galleries excavated in a carbonate substrate; often has swollen chambers with connecting canals.
* ''[[Gastrochaenolites]]'' are clavate (club-shaped) borings also produced in calcareous hard substrates, usually by [[bivalve]]s.
* ''[[Oikobesalon]]'' is an unbranched, elongate burrow with single-entrance and circular cross-section produced by terebellid polychaetes. They are covered with thin lining which has a transverse ornamentation in the form of fusiform annulation.
* ''[[Petroxestes]]'' is a shallow groove boring produced by mytilacean bivalves in carbonate hard substrates.
* ''[[Planolites]]'' is a small, 1-5mm (0.039–0.197 in), unlined and rarely branched, elongate burrow with fill that differs from the host rock, and is found throughout the [[Ediacaran]] and the [[Phanerozoic]].
* ''[[Protichnites]]'' consists of two rows of tracks and a linear depression between the two rows. The tracks are believed to have been made by the walking appendages of [[arthropod]]s. The linear depression is thought to be the result of a dragging tail. The structures bearing this name were typically made on the tidal flats of [[Paleozoic]] seas, but similar ones extend into the [[Cenozoic]].
* ''[[Rhizocorallium]]'' is a type of [[burrow]], the inclination of which is typically within 10° of the bedding planes of the sediment. These burrows can be very large, over a meter long in sediments that show good preservation, e.g. [[Jurassic]] rocks of the [[Yorkshire]] Coast (eastern [[United Kingdom]]), but the width is usually only up to {{convert|2|cm|in|frac=4}}, restricted by the size of the organisms producing it. It is thought that they represent fodinichnia as the animal (probably a [[nematode]]) scoured the [[sediment]] for food.
* ''[[Rogerella]]'' is a small pouch-shaped boring with a slit-like aperture currently produced by [[acrothoracica]]n [[barnacles]].
* ''[[Rusophycus]]'' are bilobed "resting traces" associated with trilobites and other arthropods such as horseshoe crabs.
* ''[[Skolithos]]'': One well-known occurrence of Cambrian trace fossils from this period is the famous '[[Pipe Rock]]' of northwest [[Scotland]]. The 'pipes' that give the rock its name are closely packed straight tubes- which were presumably made by some kind of [[worm]]-like organism. The name given to this type of tube or burrow is ''Skolithos'', which may be {{convert|30|cm|in|0|abbr=on}} in length and between {{convert|2|and|4|cm|in|frac=4|abbr=on}} in diameter. Such traces are known worldwide from sands and [[sandstone]]s deposited in shallow water environments, from the [[Cambrian]] period (542&ndash;488 [[annum|Ma]]) onwards.
* ''[[Thalassinoides]]'' are burrows which occur parallel to the bedding plane of the rock and are extremely abundant in rocks, worldwide, from the [[Jurassic]] period onwards. They are repeatedly branched, with a slight swelling present at the junctions of the tubes. The burrows are cylindrical and vary from {{convert|2|to|5|cm|in|frac=4|abbr=on}} in diameter. ''Thalassinoides'' sometimes contain scratch marks, droppings or the bodily remains of the [[crustacean]]s which made them.
* ''[[Teichichnus]]'' has a distinctive form produced by the stacking of thin 'tongues' of [[sediment]], atop one another. They are again believed to be fodinichnia, with the organism adopting the habit of retracing the same route through varying heights of the sediment, which would allow it to avoid going over the same area. These 'tongues' are often quite sinuous, reflecting perhaps a more nutrient-poor environment in which the feeding animals had to cover a greater area of sediment, in order to acquire sufficient nourishment.
* ''[[Tremichnus]]'' is an embedment structure (i.e. [[bioclaustration]]) formed by an organism that inhibited growth of the crinoid host stereom.
* ''[[Trypanites]]'' are elongated cylindrical [[bioerosion|boring]]s in calcareous substrates such as shells, carbonate [[hardground]]s, and [[limestones]]. Usually produced by worms of various types and [[sipunculids]].

==Other notable trace fossils==
Less ambiguous than the above ichnogenera, are the traces left behind by [[invertebrate]]s such as ''[[Hibbertopterus]]'', a giant "sea scorpion" or [[eurypterid]] of the early [[Paleozoic]] era. This marine [[arthropod]] produced a spectacular track preserved in Scotland.<ref>{{cite journal|author=Whyte, MA |year=2005 |title=Palaeoecology: A gigantic fossil arthropod trackway |journal=Nature|volume=438|pages=576 |doi=10.1038/438576a|pmid=16319874|issue=7068|bibcode = 2005Natur.438..576W |s2cid=4422644 |doi-access=free }}</ref>

[[Bioerosion]] through time has produced a magnificent record of borings, gnawings, scratchings and scrapings on hard substrates. These trace fossils are usually divided into macroborings<ref>Wilson, M.A., 2007. Macroborings and the evolution of bioerosion, pp. 356–367. In: Miller, W. III (ed.), Trace Fossils: Concepts, Problems, Prospects. Elsevier, Amsterdam, 611 pages.</ref> and microborings.<ref>Glaub, I., Golubic, S., Gektidis, M., Radtke, G. and Vogel, K., 2007. Microborings and microbial endoliths: geological implications. In: Miller III, W (ed) Trace fossils: concepts, problems, prospects. Elsevier, Amsterdam: pp. 368–381.</ref><ref>Glaub, I. and Vogel, K., 2004. The stratigraphic record of microborings. Fossils & Strata 51:126–135.</ref> Bioerosion intensity and diversity is punctuated by two events. One is called the Ordovician Bioerosion Revolution (see Wilson & Palmer, 2006) and the other was in the Jurassic.<ref>Taylor, P.D. and Wilson, M.A., 2003. Palaeoecology and evolution of marine hard substrate communities. Earth-Science Reviews 62: 1–103.{{cite web |url=http://www3.wooster.edu/geology/Taylor%26Wilson2003.pdf |title=Archived copy |access-date=2009-07-21 |archive-url=https://web.archive.org/web/20090325233234/http://www.wooster.edu/geology/Taylor%26Wilson2003.pdf |archive-date=2009-03-25 }}</ref> For a comprehensive bibliography of the bioerosion literature, please see the External links below.

The oldest types of [[tetrapod]] tail-and-footprints date back to the latter [[Devonian]] period. These [[vertebrate]] impressions have been found in [[Ireland]], [[Scotland]], [[Pennsylvania]], and [[Australia]]. A sandstone slab containing the track of tetrapod, dated to 400 million years, is amongst the oldest evidence of a vertebrate walking on land.<ref name="Vickers-Rich1993">{{cite book |last1=Vickers-Rich |first1=P. |title=Wildlife of Gondwana |date=1993 |publisher=Reed |location=NSW |isbn=0-7301-0315-3 |pages=103–104}}</ref>

Important [[human evolution|human]] trace fossils are the [[Laetoli]] ([[Tanzania]]) footprints, imprinted in volcanic ash 3.7 [[annum|Ma]] (million years ago) – probably by an early [[Australopithecus]].<ref name=RaichlenEtal1010>{{Cite journal|year=2010 |author=David A. Raichlen |author2=Adam D. Gordon |author3=William E. H. Harcourt-Smith |author4=Adam D. Foster |author5=Wm. Randall Haas Jr |title=Laetoli Footprints Preserve Earliest Direct Evidence of Human-Like Bipedal Biomechanics |journal=PLOS ONE |volume=5 |issue=3 |page= e9769 |doi=10.1371/journal.pone.0009769|pmid=20339543|pmc=2842428|editor1-last=Rosenberg|editor1-first=Karen|bibcode=2010PLoSO...5.9769R |doi-access=free }}</ref>

== Confusion with other types of fossils ==
[[Image:AsteriacitesDevonianOhio.jpg|thumb|''[[Asteriacites]]'' (sea star trace fossil) from the [[Devonian]] of northeastern Ohio. It appears at first to be an external mold of the body, but the sediment piled between the rays shows that it is a burrow.]]
Trace fossils are not body casts. The [[Ediacara biota]], for instance, primarily comprises the casts of organisms in sediment. Similarly, a footprint is not a simple replica of the sole of the foot, and the resting trace of a seastar has different details than an impression of a seastar.

Early paleobotanists misidentified a wide variety of structures they found on the bedding planes of [[sedimentary rocks]] as fucoids ([[Fucales]], a kind of [[brown algae]] or [[seaweed]]). However, even during the earliest decades of the study of ichnology, some fossils were recognized as animal footprints and burrows. Studies in the 1880s by [[A. G. Nathorst]] and [[Joseph F. James]] comparing 'fucoids' to modern traces made it increasingly clear that most of the specimens identified as fossil fucoids were animal trails and burrows. True fossil fucoids are quite rare.

[[Pseudofossil]]s, which are ''not'' true fossils, should also not be confused with ichnofossils, which are true indications of prehistoric life.

==Gallery of trace fossils==
<gallery widths="180" heights="180">
File:FaringdonCobble.JPG|Numerous borings in a [[Cretaceous]] cobble, [[Faringdon]], England; see Wilson (1986)
File:BoredEncrustedShell.JPG|Sponge borings (''[[Entobia]]'') and encrusters on a modern bivalve shell, North Carolina
File:Entobia Prairie Bluff Chalk Formation Cretaceous.JPG|''Entobia'' from the [[Prairie Bluff Chalk Formation]] (Upper [[Cretaceous]]). Preserved as a cast of the excavations.
File:Gyrochorte convex epirelief.jpg|Trace fossil ''Gyrochorte'' from the [[Carmel Formation]] (Middle Jurassic) of SW Utah
File:Helminthopsis01.JPG|''Helminthopsis'' ichnosp., a trace fossil from the [[Logan Formation]] (Lower [[Carboniferous]]) of [[Wooster, Ohio]]
File:Gigandipus.JPG|''Gigandipus'', a [[dinosaur]] footprint in the Lower [[Jurassic]] Moenave Formation at the [[St. George Dinosaur Discovery Site]] at Johnson Farm, southwestern [[Utah]]
File:CretaceousLockeia121911.jpg|''Lockeia'' from the [[Dakota Formation]] (Upper Cretaceous)
File:DevonianLockeia121911.jpg|''Lockeia'' from the [[Chagrin Shale]] (Upper Devonian) of northeastern [[Ohio]]. This is an example of the trace fossil ethological group [[Fugichnia]].
File:Gnathichnus Cenomanian 020413.JPG|''[[Gnathichnus|Gnathichnus pentax]]'' echinoid trace fossil on an oyster from the [[Cenomanian]] of [[Hamakhtesh Hagadol]], southern Israel
File:Naticid borehole Calvert.jpg|Naticid boring in ''Stewartia'' from the Calvert Formation, Zone 10, Calvert County, Maryland (Miocene)
File:Trace fossils Bull Fork Ordovician OH.JPG|Trace fossils as convex hyporeliefs on bottom of bed; Bull Fork Formation (Upper Ordovician); Caesar Creek, Ohio
File:Tridactyl ornithopod dinosaur track YORYM-1998.335.JPG|Inverted trace fossil of an unidentified [[tridactyl]] [[ornithopod]]
File:trilha presente no Monumento Natural dos Lagosteiros.jpg|The main dinosaur trackway at the [[Lagosteiros Natural Monument]] site
</gallery>

==History==
[[Charles Darwin]]'s ''[[The Formation of Vegetable Mould through the Action of Worms]]''{{efn|{{Citation| last = Darwin | first =C. R. | year = 1881 | title =The formation of vegetable mould, through the action of worms, with observations on their habits | location = London | publisher =John Murray | url =http://darwin-online.org.uk/EditorialIntroductions/Freeman_VegetableMouldandWorms.html | access-date =26 September 2014 }}}} is an example of a very early work on ichnology, describing [[bioturbation]] and, in particular, the burrowing of [[earthworms]].<ref name="Donovan">{{cite book|editor1-last=Donovan|editor1-first=Stephen K.|title=The Palaeobiology of Trace Fossils|publisher=John Wiley & Sons|isbn=978-0-471-94843-8|year=1994}}</ref>

== See also ==
{{Div col}}
* {{annotated link|20th century in ichnology}}
* {{annotated link|Bioerosion}}
*[[Brutalichnus]] 
* {{annotated link|Bird ichnology}}
* {{annotated link|Burrow fossil}}
* {{annotated link|Egg fossil}}
* {{annotated link|Ichnite}} - fossilized footprints
* {{annotated link|List of index fossils|Index fossil}}
* {{annotated link|List of non-Dinosauria fossil trackway articles}}
* {{annotated link|Neoichnology}}
* {{annotated link|Spoor (animal)}}
* {{annotated link|Trace fossil classification}}
* {{annotated link|Underprint (ichnology)}}
* {{annotated link|Way up structure}}

{{Div col end}}

== References ==
{{Reflist}}

== Further reading ==
{{Notelist}}
{{refbegin}}
* Bromley, R.G., 1970. "Borings as trace fossils and ''[[Entobia]] cretacea'' Portlock as an example", pp.&nbsp;49–90. In: Crimes, T.P. and Harper, J.C. (eds.), ''Trace Fossils''. Geological Journal Special Issue 3.
* Bromley, R.G., 2004. "A stratigraphy of marine bioerosion". In: The application of ichnology to palaeoenvironmental and stratigraphic analysis. (Ed.D. McIlroy), Geological Society of London, Special Publications 228:455–481.
* Palmer, T.J., 1982. "Cambrian to Cretaceous changes in hardground communities". Lethaia 15:309–323.
* {{cite book |first=Adolf|last=Seilacher|author-link=Adolf Seilacher |year=2007 |title=Trace Fossil Analysis |publisher=Springer-Verlag |page=[https://archive.org/details/tracefossilanaly00seil/page/n237 226] p |no-pp=yes |isbn=978-3-540-47225-4 |url=https://archive.org/details/tracefossilanaly00seil|url-access=limited}}
* {{cite journal
 |author1=Vinn, O. |author2=Wilson, M.A.
 |name-list-style=amp |title=Occurrence of giant borings of Osprioneides kampto in the lower Silurian (Sheinwoodian) stromatoporoids of Saaremaa, Estonia
 |journal=Ichnos 
 |year=2010
 |volume=17
 |issue=3
 |pages=166–171
 |url = https://www.researchgate.net/publication/222089796
 |access-date = 2014-01-10
 |doi = 10.1080/10420940.2010.502478
|s2cid=128990588
 }}
* Wilson, M.A., 1986. "Coelobites and spatial refuges in a Lower Cretaceous cobble-dwelling hardground fauna". Palaeontology 29:691–703.
* Wilson, M.A. and Palmer, T.J., 2006. "Patterns and processes in the Ordovician Bioerosion Revolution". Ichnos 13: 109–112.[https://web.archive.org/web/20081216220233/http://www.wooster.edu/geology/WilsonPalmer06.pdf]
* Yochelson, E.L. and Fedonkin, M.A., 1993. Paleobiology of ''Climactichnites'', and Enigmatic Late Cambrian Fossil. Smithsonian Contributions to Paleobiology 74:1–74.
{{refend}}

== External links ==
{{Commons category|Trace fossils}}
* [https://web.archive.org/web/20090416063931/http://www.peripatus.gen.nz/paleontology/trafos.html Encyclopaedia-style article about trace fossils]
* [https://web.archive.org/web/20080914223236/http://www.envs.emory.edu/faculty/MARTIN/ichnology/images.htm Ichnogenus images]
* [http://www.clastics.com/ichnogenera.htm Chuck D. Howell's Ichnogenera Photos]
* [https://ichnology.ku.edu/poi/poi/glossary.html Glossary of Ichnology Terms]

{{Authority control}}

{{DEFAULTSORT:Trace Fossil}}
[[Category:Trace fossils| ]]
[[Category:Paleozoology]]
[[Category:Bioindicators]]