Trace fossil
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A trace fossil, also known as an ichnofossil (
Trace fossils may consist of physical impressions made on or in the
The term in its broadest sense also includes the remains of other organic material produced by an organism; for example
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
Occurrence
Traces are better known in their fossilized form than in modern sediments.[1] This makes it difficult to interpret some fossils by comparing them with modern traces, even though they may be extant or even common.[1] The main difficulties in accessing extant burrows stem from finding them in consolidated sediment, and being able to access those formed in deeper water.
Trace fossils are best preserved in sandstones;[1] the grain size and depositional facies both contributing to the better preservation. They may also be found in shales and limestones.[1]
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:[1]
- 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.
- 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 Recent termite mounds, which can encompass several square kilometers of sediment
Information provided by ichnofossils
Trace fossils are important paleoecological and paleoenvironmental indicators, because they are preserved
Paleoecology
Trace fossils provide us with indirect evidence of
Trace fossils are formed by organisms performing the functions of their everyday life, such as walking, crawling, burrowing, boring, or feeding.
Perhaps the most spectacular trace fossils are the huge, three-toed footprints produced by
However, most trace fossils are rather less conspicuous, such as the trails made by
Paleoenvironment
Fossil footprints made by tetrapod vertebrates 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 amphibians, reptiles, mammals, or birds 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.[4]
Assemblages of trace fossils occur at certain water depths,[1] and can also reflect the salinity and turbidity of the water column.
Stratigraphic correlation
Some trace fossils can be used as local
The base of the
Trace fossils have a further utility, as many appear before the organism thought to create them, extending their stratigraphic range.[7]
Ichnofacies
Inherent bias
Most trace fossils are known from marine deposits.[12] 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
Evolution
The earliest complex trace fossils, not including microbial traces such as
The first evidence of burrowing which is widely accepted dates to the
As the Cambrian got underway, new forms of trace fossil appeared, including vertical burrows (e.g. Diplocraterion) and traces normally attributed to arthropods.[26] These represent a "widening of the behavioural repertoire",[27] both in terms of abundance and complexity.[28]
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,
Further, less rapid[verification needed] diversification occurred since,[verification needed] and many traces have been converged upon independently by unrelated groups of organisms.[1]
Trace fossils also provide our earliest evidence of animal life on land.
Common ichnogenera
- 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.[33]
- 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 (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.
- 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.
- spongesconsisting of galleries excavated in a carbonate substrate; often has swollen chambers with connecting canals.
- bivalves.
- 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 arthropods. 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 2 centimetres (3⁄4 in), 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.
- barnacles.
- Rusophycus are bilobed "resting traces" associated with trilobites and other arthropods such as horseshoe crabs.
- 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 2 to 5 cm (3⁄4 to 2 in) in diameter. Thalassinoides sometimes contain scratch marks, droppings or the bodily remains of the crustaceans 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.
- sipunculids.
Other notable trace fossils
Less ambiguous than the above ichnogenera, are the traces left behind by invertebrates such as Hibbertopterus, a giant "sea scorpion" or eurypterid of the early Paleozoic era. This marine arthropod produced a spectacular track preserved in Scotland.[36]
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[37] and microborings.[38][39] 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.[40] 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.[41]
Important
Confusion with other types of fossils
Trace fossils are not body casts. The
Early paleobotanists misidentified a wide variety of structures they found on the bedding planes of
Pseudofossils, which are not true fossils, should also not be confused with ichnofossils, which are true indications of prehistoric life.
Gallery of trace fossils
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Numerous borings in a Cretaceous cobble, Faringdon, England; see Wilson (1986)
-
Sponge borings (Entobia) and encrusters on a modern bivalve shell, North Carolina
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Entobia from thePrairie Bluff Chalk Formation (Upper Cretaceous). Preserved as a cast of the excavations.
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Trace fossil Gyrochorte from the Carmel Formation (Middle Jurassic) of SW Utah
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Helminthopsis ichnosp., a trace fossil from the Logan Formation (Lower Carboniferous) of Wooster, Ohio
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Gigandipus, a dinosaur footprint in the Lower Jurassic Moenave Formation at the St. George Dinosaur Discovery Site at Johnson Farm, southwestern Utah
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Lockeia from the Dakota Formation (Upper Cretaceous)
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Lockeia from the Chagrin Shale (Upper Devonian) of northeastern Ohio. This is an example of the trace fossil ethological group Fugichnia.
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Hamakhtesh Hagadol, southern Israel
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Naticid boring in Stewartia from the Calvert Formation, Zone 10, Calvert County, Maryland (Miocene)
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Trace fossils as convex hyporeliefs on bottom of bed; Bull Fork Formation (Upper Ordovician); Caesar Creek, Ohio
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Inverted trace fossil of an unidentifiedornithopod
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The main dinosaur trackway at the Lagosteiros Natural Monument site
History
See also
- 20th century in ichnology – ichnology-related events during the 20th century
- Bioerosion – Erosion of hard substrates by living organisms
- Brutalichnus
- Bird ichnology – study of avian life traces in ornithology and paleontology
- Burrow fossil – Trace fossil
- Egg fossil – Fossilized remains of eggs laid by ancient animals
- Ichnite– Fossilized footprint (ichnite) - fossilized footprints
- Index fossil – Fossils used to define and identity geologic periods
- List of non-Dinosauria fossil trackway articles
- Neoichnology – the study of modern/contemporary traces resultant from the behavior of biological organisms
- Spoor (animal) – any sign of a creature or trace by which the progress of someone or something may be followed; may include tracks, scents, scat, or broken foliage
- Trace fossil classification – describes taxonomic/morphological, ethological, and topological systems for classifying trace fossils
- Underprint (ichnology) – Type of fossil footprints
- Way up structure
References
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- ISBN 978-0-13-154728-5. Archived from the original(PDF) on 2016-03-31. Retrieved 2017-02-01.
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- ^ ISBN 978-0-13-154728-5. Archived from the original(PDF) on 2016-03-31. Retrieved 2017-02-01.
- ^ ISBN 978-1-897095-50-8.
- ISSN 1502-3931.
- ISBN 978-0-444-52949-7.
- ^ Saether, Kristian; Christopher Clowes. "Trace Fossils". Archived from the original on 2009-04-16. Retrieved 2009-06-19.
- S2CID 1922434.
- PMID 9756480.
- S2CID 39772232.
- S2CID 129734373.
- ^ Frances S. Dunn and Alex G. Liu (2017). "Fossil Focus: The Ediacaran Biota". Paleontology Online.
- )
- ^
Dzik, J (2007), "The Verdun Syndrome: simultaneous origin of protective armour and infaunal shelters at the Precambrian–Cambrian transition", in Vickers-Rich, Patricia; Komarower, Patricia (eds.), The Rise and Fall of the Ediacaran Biota, Special publications, vol. 286, London: Geological Society, pp. 405–414, OCLC 156823511
- ^ 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)
- ^ Grazhdankin, D. V.; A. Yu. Ivantsov (1996). "Reconstruction of biotopes of ancient Metazoa of the Late Vendian White Sea Biota". Paleontological Journal. 30: 676–680.
- ISSN 1028-334X. Archived from the original(PDF) on 2007-07-04. Retrieved 2007-05-10.
- ^ A. Yu. Ivantsov. (2008). "Feeding traces of the Ediacaran animals". HPF-17 Trace fossils ? ichnological concepts and methods. International Geological Congress - Oslo 2008.
- OCLC 156823511
- S2CID 1019572.
- S2CID 130340569. Retrieved 2007-09-09.
- S2CID 10491968.
- PMID 21680425.
- doi:10.1139/z01-211. Archived from the original(PDF) on 2007-09-27. Retrieved 2007-04-21. most Cambrian trace fossils have been assigned to bilaterian animals.
- ^ "Life on terra firma began with an invasion". Phys.org News. Retrieved 2017-06-04.
- S2CID 130821454.
- S2CID 129234373.
- ^ Vinn, O.; Wilson, M.A.; Zatoń, M.; Toom, U. (2014). "The trace fossil Arachnostega in the Ordovician of Estonia (Baltica)". Palaeontologia Electronica. 17.3.40A: 1–9. Retrieved 2014-06-10.
- S2CID 129182104.
- S2CID 129732925.
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- ^ 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.
- ^ 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.
- ^ Glaub, I. and Vogel, K., 2004. The stratigraphic record of microborings. Fossils & Strata 51:126–135.
- ^ Taylor, P.D. and Wilson, M.A., 2003. Palaeoecology and evolution of marine hard substrate communities. Earth-Science Reviews 62: 1–103."Archived copy" (PDF). Archived from the original (PDF) on 2009-03-25. Retrieved 2009-07-21.
{{cite web}}
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Further reading
- ^ Darwin, C. R. (1881), The formation of vegetable mould, through the action of worms, with observations on their habits, London: John Murray, retrieved 26 September 2014
- Bromley, R.G., 1970. "Borings as trace fossils and Entobia cretacea Portlock as an example", pp. 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.
- ISBN 978-3-540-47225-4.
- Vinn, O. & Wilson, M.A. (2010). "Occurrence of giant borings of Osprioneides kampto in the lower Silurian (Sheinwoodian) stromatoporoids of Saaremaa, Estonia". Ichnos. 17 (3): 166–171. S2CID 128990588. Retrieved 2014-01-10.
- 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.[1]
- Yochelson, E.L. and Fedonkin, M.A., 1993. Paleobiology of Climactichnites, and Enigmatic Late Cambrian Fossil. Smithsonian Contributions to Paleobiology 74:1–74.