Editing Trace fossil (section)

== 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>