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Taphonomy is the study of how
organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fu ...
s decay and become
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
ized or preserved in the paleontological record. The term ''taphonomy'' (from
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
, 'burial' and , 'law') was introduced to
paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...
in 1940 by Soviet scientist Ivan Efremov to describe the study of the transition of remains, parts, or products of
organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fu ...
s from the
biosphere The biosphere (from Greek βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all ecosystems. It can also ...
to the
lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of up to thousands of years ...
. The term taphomorph is used to describe fossil structures that represent poorly-preserved, deteriorated remains of a mixture of
taxonomic groups In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given ...
, rather than of a single one.


Description

Taphonomic phenomena are grouped into two phases: biostratinomy, events that occur between death of the organism and the burial; and
diagenesis Diagenesis () is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a ...
, events that occur after the burial. Since Efremov's definition, taphonomy has expanded to include the fossilization of organic and inorganic materials through both cultural and environmental influences. This is a multidisciplinary concept and is used in slightly different contexts throughout different fields of study. Fields that employ the concept of taphonomy include: *
Archaeobotany Paleoethnobotany (also spelled palaeoethnobotany), or archaeobotany, is the study of past human-plant interactions through the recovery and analysis of ancient plant remains. Both terms are synonymous, though paleoethnobotany (from the Greek words ...
*
Archaeology Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, biofacts or ecofacts, sites, and cultural landsc ...
*
Biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary ...
*
Forensic science Forensic science, also known as criminalistics, is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and criminal ...
*
Geoarchaeology Geoarchaeology is a multi-disciplinary approach which uses the techniques and subject matter of geography, geology, geophysics and other Earth sciences to examine topics which inform archaeological knowledge and thought. Geoarchaeologists study ...
*
Geology Geology () is a branch of natural science concerned with Earth and other Astronomical object, astronomical objects, the features or rock (geology), rocks of which it is composed, and the processes by which they change over time. Modern geology ...
* Paleoecology *
Paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...
* Zooarchaeology There are five main stages of taphonomy: disarticulation, dispersal, accumulation, fossilization, and mechanical alteration. The first stage, disarticulation, occurs as the organism decays and the bones are no longer held together by the flesh and tendons of the organism. Dispersal is the separation of pieces of an organism caused by natural events (i.e. floods, scavengers etc.). Accumulation occurs when there is a buildup of organic and/or inorganic materials in one location (scavengers or human behavior). When mineral rich groundwater permeates organic materials and fills the empty spaces, a fossil is formed. The final stage of taphonomy is mechanical alteration; these are the processes that physically alter the remains (i.e. freeze-thaw, compaction, transport, burial). It should be added that these "stages" are not only successive, they interplay. For example, chemical changes occur at every stage of the process, because of bacteria. "Changes" begin as soon as the death of the organism: enzymes are released that destroy the organic contents of the tissues, and mineralised tissues such as bone, enamel and
dentin Dentin () (American English) or dentine ( or ) (British English) ( la, substantia eburnea) is a calcified tissue of the body and, along with enamel, cementum, and pulp, is one of the four major components of teeth. It is usually covered by e ...
are a mixture of organic and mineral components. Moreover, most often the organisms (vegetal or animal) are dead because they have been "killed" by a predator. The digestion modifies the composition of the flesh, but also that of the bones.


Research areas

Taphonomy has undergone an explosion of interest since the 1980s, with research focusing on certain areas. *
Microbial A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
, biogeochemical, and larger-scale controls on the preservation of different tissue types; in particular, exceptional preservation in Konzervat-lagerstätten. Covered within this field is the dominance of biological versus physical agents in the destruction of remains from all major taxonomic groups (plants, invertebrates, vertebrates). * Processes that concentrate biological remains; especially the degree to which different types of assemblages reflect the species composition and abundance of source faunas and floras. *Actualistic taphonomy uses the present to understand past taphonomic events. This is often done through controlled experiments, such as the role microbes play in fossilization, the effects of mammalian carnivores on bone, or the burial of bone in a water flume. Computer modeling is also used to explain taphonomic events. * The spatio-temporal resolution and ecological fidelity of species assemblages, particularly the relatively minor role of out-of-habitat transport contrasted with the major effects of time-averaging. * The outlines of megabiases in the
fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
, including the evolution of new bauplans and behavioral capabilities, and by broad-scale changes in climate, tectonics, and geochemistry of Earth surface systems. * The
Mars Science Laboratory Mars Science Laboratory (MSL) is a robotic space probe mission to Mars launched by NASA on November 26, 2011, which successfully landed ''Curiosity'', a Mars rover, in Gale Crater on August 6, 2012. The overall objectives include investigati ...
mission objectives evolved from assessment of ancient Mars habitability to developing predictive models on taphonomy.


Paleontology

One motivation behind taphonomy is to understand biases present in the
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
record better. Fossils are ubiquitous in sedimentary rocks, yet
paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...
s cannot draw the most accurate conclusions about the lives and ecology of the fossilized organisms without knowing about the processes involved in their fossilization. For example, if a fossil assemblage contains more of one type of fossil than another, one can infer either that the organism was present in greater numbers, or that its remains were more resistant to decomposition. During the late twentieth century, taphonomic data began to be applied to other paleontological subfields such as paleobiology,
paleoceanography Paleoceanography is the study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation and biological productivity. Paleoceanographic studies using environment models ...
, ichnology (the study of trace fossils) and
biostratigraphy Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of ...
. By coming to understand the
oceanographic Oceanography (), also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamic ...
and ethological implications of observed taphonomic patterns, paleontologists have been able to provide new and meaningful interpretations and correlations that would have otherwise remained obscure in the
fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
.


Forensic science

Forensic taphonomy is a relatively new field that has increased in popularity in the past 15 years. It is a subfield of
forensic anthropology Forensic anthropology is the application of the anatomical science of anthropology and its various subfields, including forensic archaeology and forensic taphonomy, in a legal setting. A forensic anthropologist can assist in the identification ...
focusing specifically on how taphonomic forces have altered criminal evidence. There are two different branches of forensic taphonomy
biotaphonomy
an

Biotaphonomy looks at how the decomposition and/or destruction of the organism has happened. The main factors that affect this branch are categorized into three groups: environmental factors; external variables, individual factors; factors from the organism itself (i.e. body size, age, etc.), and cultural factors; factors specific to any cultural behaviors that would affect the decomposition (burial practices). Geotaphonomy studies how the burial practices and the burial itself affects the surrounding environment. This includes soil disturbances and tool marks from digging the grave, disruption of plant growth and
soil pH Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the ne ...
from the decomposing body, and the alteration of the land and water drainage from introducing an unnatural mass to the area. This field is extremely important because it helps scientists use the taphonomic profile to help determine what happened to the remains at the time of death
perimortem
and after death
postmortem
. This can make a huge difference when considering what can be used as evidence in a criminal investigation.


Environmental archaeology

Archaeologists study taphonomic processes in order to determine how plant and animal (including human) remains accumulate and differentially preserve within archaeological sites.
Environmental archaeology Environmental archaeology is a sub-field of archaeology which emerged in 1970s and is the science of reconstructing the relationships between past societies and the environments they lived in. The field represents an archaeological-palaeoecologica ...
is a multidisciplinary field of study that focuses on understanding the past relationships between groups and their environments. The main subfields of environmental archaeology include zooarchaeology,
paleobotany Paleobotany, which is also spelled as palaeobotany, is the branch of botany dealing with the recovery and identification of plant remains from geological contexts, and their use for the biological reconstruction of past environments (paleogeog ...
, and
geoarchaeology Geoarchaeology is a multi-disciplinary approach which uses the techniques and subject matter of geography, geology, geophysics and other Earth sciences to examine topics which inform archaeological knowledge and thought. Geoarchaeologists study ...
. Taphonomy allows specialists to identify what artifacts or remains encountered before and after initial burial. Zooarchaeology, a focus within environmental archaeology investigates taphonomic processes on animal remains. The processes most commonly identified within zooarchaeology include thermal alteration (burns), cut marks, worked bone, and gnaw marks.Fernandez Jalvo, Yolanda and Peter Andrews, “Methods in Taphonomy” in Atlas of Taphonomic Identifications: 1001+ Images of Fossil and Recent Mammal Bone Modification, ed. Eric Delson and Eric J. Sargis Vertebrate Paleobiology and Paleoanthropology Series (New York, NY, American Museum of Natural History, 2016). Thermally altered bone indicate the use of fire and animal processing. Cut marks and worked bone can inform zooarchaeologists on tool use or food processing. When there is little to no written record, taphonomy allows environmental archaeologists to better comprehend the ways in which a group interacted with their surrounding environments and inhabitants. The field of environmental archaeology provides crucial information for attempting to understand the resilience of past societies and the great impacts that environmental shifts can have on a population. Knowledge gained from the past through these studies can be used to inform present and future decisions for human-environment interactions.


Microbial Mats

Modern experiments have been conducted on post-mortem invertebrates and vertebrates to understand how microbial mats and microbial activity influence the formation of fossils and the preservation of soft tissues. In these studies, microbial mats entomb animal carcasses in a sarcophagus of microbes—the sarcophagus entombing the animal's carcass delays decay. Entombed carcasses were observed to be more intact than non-entombed counter-parts by years at a time. Microbial mats maintained and stabilized the articulation of the joints and the skeleton of post-mortem organisms, as seen in frog carcasses for up to 1080 days after coverage by the mats. The environment within the entombed carcasses is typically described as anoxic and acidic during the initial stage of decomposition. These conditions are perpetuated by the exhaustion of oxygen by aerobic bacteria within the carcass creating an environment ideal for the preservation of soft tissues, such as muscle tissue and brain tissue. The anoxic and acidic conditions created by that mats also inhibit the process of autolysis within the carcasses delaying decay even further.  Endogenous gut bacteria have also been described to aid the preservation of invertebrate soft tissue by delaying decay and stabilizing soft tissue structures. Gut bacteria form pseudomorphs replicating the form of soft tissues within the animal. These
pseudomorph In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form ( crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced ...
s are possible explanation for the increased occurrence of preserved guts impression among invertebrates. In the later stages of the prolonged decomposition of the carcasses, the environment within the sarcophagus alters to more oxic and basic conditions promoting
biomineralization Biomineralization, also written biomineralisation, is the process by which living organisms produce minerals, often to harden or stiffen existing tissues. Such tissues are called mineralized tissues. It is an extremely widespread phenomenon; ...
and the precipitation of calcium carbonate. Microbial mats additionally play a role in the formation of molds and impressions of carcasses. These molds and impressions replicate and preserve the integument of animal carcasses. The degree to which has been demonstrated in frog skin preservation. The original morphology of the frog skin, including structures such as warts, was preserved for more than 1.5 years. The microbial mats also aided in the formation of the mineral
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...
embedded within the frog skin. The microbes that constitute the microbial mats in addition to forming a sarcophagus, secrete an exopolymeric substances (EPS) that drive biomineralization. The EPS provides a nucleated center for biomineralization. During later stages of decomposition heterotrophic microbes degrade the EPS, facilitating the release of calcium ions into the environment and creating a Ca-enriched film. The degradation of the EPS and formation of the Ca-rich film is suggested to aid in the precipitation of calcium carbonate and further the process of biomineralization.


Taphonomic biases in the fossil record

Because of the very select processes that cause preservation, not all organisms have the same chance of being preserved. Any factor that affects the likelihood that an organism is preserved as a fossil is a potential source of bias. It is thus arguably the most important goal of taphonomy to identify the scope of such biases such that they can be quantified to allow correct interpretations of the relative abundances of organisms that make up a fossil biota. Some of the most common sources of bias are listed below.


Physical attributes of the organism itself

This perhaps represents the biggest source of bias in the fossil record. First and foremost, organisms that contain hard parts have a far greater chance of being represented in the fossil record than organisms consisting of soft tissue only. As a result, animals with bones or shells are overrepresented in the fossil record, and many plants are only represented by
pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametop ...
or
spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...
s that have hard walls. Soft-bodied organisms may form 30% to 100% of the biota, but most fossil assemblages preserve none of this unseen diversity, which may exclude groups such as
fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...
and entire animal
phyla Phyla, the plural of ''phylum'', may refer to: * Phylum, a biological taxon between Kingdom and Class * by analogy, in linguistics, a large division of possibly related languages, or a major language family which is not subordinate to another Phy ...
from the fossil record. Many animals that
moult In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
, on the other hand, are overrepresented, as one animal may leave multiple fossils due to its discarded body parts. Among plants,
wind-pollinated Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Almost all gymnosperms are anemophilous, as are many plants in the order Poales, including grasses, sedges, and rushes. Other common anemophilo ...
species produce so much more pollen than animal-pollinated species, the former being overrepresented relative to the latter.


Characteristics of the habitat

Most fossils form in conditions where material is deposited on the bottom of water bodies. Coastal areas are often prone to high rates of erosion, and rivers flowing into the sea may carry a high particulate load from inland. These sediments will eventually settle out, so organisms living in such environments have a much higher chance of being preserved as fossils after death than do those organisms living in non-depositing conditions. In continental environments, fossilization is likely in lakes and riverbeds that gradually fill in with organic and inorganic material. The organisms of such habitats are also liable to be overrepresented in the fossil record than those living far from these aquatic environments where burial by sediments is unlikely to occur.


Mixing of fossils from different places

A
sedimentary Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
deposit may have experienced a mixing of noncontemporaneous remains within single sedimentary units via physical or biological processes; i.e. a deposit could be ripped up and redeposited elsewhere, meaning that a deposit may contain a large number of fossils from another place (an allochthonous deposit, as opposed to the usual autochthonous). Thus, a question that is often asked of fossil deposits is to what extent does the fossil deposit record the true biota that originally lived there? Many fossils are obviously autochthonous, such as rooted fossils like crinoids, and many fossils are intrinsically obviously allochthonous, such as the presence of photoautotrophic plankton in a benthic deposit that must have sunk to be deposited. A fossil deposit may thus become biased towards exotic species (i.e. species not endemic to that area) when the sedimentology is dominated by gravity-driven surges, such as mudslides, or may become biased if there are very few endemic organisms to be preserved. This is a particular problem in
palynology Palynology is the "study of dust" (from grc-gre, παλύνω, palynō, "strew, sprinkle" and ''-logy'') or of "particles that are strewn". A classic palynologist analyses particulate samples collected from the air, from water, or from deposit ...
.


Temporal resolution

Because population turnover rates of individual taxa are much less than net rates of sediment accumulation, the biological remains of successive, noncontemporaneous populations of organisms may be admixed within a single bed, known as time-averaging. Because of the slow and episodic nature of the geologic record, two apparently contemporaneous fossils may have actually lived centuries, or even millennia, apart. Moreover, the ''degree'' of time-averaging in an assemblage may vary. The degree varies on many factors, such as tissue type, the habitat, the frequency of burial events and exhumation events, and the depth of
bioturbation Bioturbation is defined as the reworking of soils and sediments by animals or plants. It includes burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a ...
within the sedimentary column relative to net sediment accumulation rates. Like biases in spatial fidelity, there is a bias towards organisms that can survive reworking events, such as shells. An example of a more ideal deposit with respect to time-averaging bias would be a
volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer ...
deposit, which captures an entire biota caught in the wrong place at the wrong time (e.g. the
Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleoz ...
Herefordshire lagerstätte).


Gaps in time series

The geological record is very discontinuous, and deposition is episodic at all scales. At the largest scale, a sedimentological high-stand period may mean that no deposition may occur for millions of years and, in fact, erosion of the deposit may occur. Such a hiatus is called an
unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...
. Conversely, a catastrophic event such as a mudslide may overrepresent a time period. At a shorter scale, scouring processes such as the formation of ripples and dunes and the passing of
turbidity current A turbidity current is most typically an underwater current of usually rapidly moving, sediment-laden water moving down a slope; although current research (2018) indicates that water-saturated sediment may be the primary actor in the process. T ...
s may cause layers to be removed. Thus the fossil record is biased towards periods of greatest sedimentation; periods of time that have less sedimentation are consequently less well represented in the fossil record. A related problem is the slow changes that occur in the depositional environment of an area; a deposit may experience periods of poor preservation due to, for example, a lack of biomineralizing elements. This causes the taphonomic or diagenetic obliteration of fossils, producing gaps and condensation of the record.


Consistency in preservation over geologic time

Major shifts in intrinsic and extrinsic properties of organisms, including morphology and behaviour in relation to other organisms or shifts in the global environment, can cause secular or long-term cyclic changes in preservation ( megabias).


Human biases

Much of the incompleteness of the fossil record is due to the fact that only a small amount of rock is ever exposed at the surface of the Earth, and not even most of that has been explored. Our fossil record relies on the small amount of exploration that has been done on this. Unfortunately, paleontologists as humans can be very biased in their methods of collection; a bias that must be identified. Potential sources of bias include, *Search images: field experiments have shown that paleontologists working on, say fossil clams are better at collecting clams than anything else because their search image has been shaped to bias them in favour of clams. *Relative ease of extraction: fossils that are easy to obtain (such as many phosphatic fossils that are easily extracted ''en masse'' by dissolution in acid) are overabundant in the fossil record. *Taxonomic bias: fossils with easily discernible morphologies will be easy to distinguish as separate species, and will thus have an inflated abundance.


Preservation of biopolymers

The taphonomic pathways involved in relatively inert substances such as calcite (and to a lesser extent bone) are relatively obvious, as such body parts are stable and change little through time. However, the preservation of "soft tissue" is more interesting, as it requires more peculiar conditions. While usually only biomineralised material survives fossilisation, the preservation of soft tissue is not as rare as sometimes thought. Both DNA and proteins are unstable, and rarely survive more than hundreds of thousands of years before degrading. Polysaccharides also have low preservation potential, unless they are highly cross-linked; this interconnection is most common in structural tissues, and renders them resistant to chemical decay. Such tissues include wood (
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity a ...
), spores and pollen ( sporopollenin), the cuticles of plants ( cutan) and animals, the cell walls of algae ( algaenan), and potentially the polysaccharide layer of some
lichens A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.kerogen Kerogen is solid, insoluble organic matter in sedimentary rocks. Comprising an estimated 1016 tons of carbon, it is the most abundant source of organic compounds on earth, exceeding the total organic content of living matter 10,000-fold. It ...
or short (<17 C atoms) aliphatic/aromatic carbon molecules. Other factors affect the likelihood of preservation; for instance sclerotization renders the jaws of
polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made ...
s more readily preserved than the chemically equivalent but non-sclerotized body cuticle. It was thought that only tough, cuticle type soft tissue could be preserved by
Burgess Shale type preservation The Burgess Shale of British Columbia is famous for its exceptional preservation of mid-Cambrian organisms. Around 69 other sites have been discovered of a similar age, with soft tissues preserved in a similar, though not identical, fashion. Addit ...
, but an increasing number of organisms are being discovered that lack such cuticle, such as the probable chordate '' Pikaia'' and the shellless '' Odontogriphus''. It is a common misconception that anaerobic conditions are necessary for the preservation of soft tissue; indeed much decay is mediated by sulfate reducing bacteria which can only survive in anaerobic conditions. Anoxia does, however, reduce the probability that scavengers will disturb the dead organism, and the activity of other organisms is undoubtedly one of the leading causes of soft-tissue destruction. Plant cuticle is more prone to preservation if it contains cutan, rather than
cutin Cutin is one of two waxy polymers that are the main components of the plant cuticle, which covers all aerial surfaces of plants. It is an insoluble substance with waterproof quality. Cutin also harbors cuticular waxes, which assist in cuticle st ...
. Plants and algae produce the most preservable compounds, which are listed according to their preservation potential by Tegellaar (see reference).


Disintegration

How complete fossils are was once thought to be a proxy for the energy of the environment, with stormier waters leaving less articulated carcasses. However, the dominant force actually seems to be predation, with scavengers more likely than rough waters to break up a fresh carcass before it is buried. Sediments cover smaller fossils faster so they are likely to be found fully articulated. However, erosion also tends to destroy smaller fossils more easily.


Distortion

Often fossils, particularly those of verterbates, are distorted by the subsequent movements of the surrounding sediment, this can include compression of the fossil in a particular axis, as well as shearing.


Significance

Taphonomic processes allow researchers of multiple fields to identify the past of natural and cultural objects. From the time of death or burial until excavation, taphonomy can aid in the understanding of past environments.Lyman, R. Lee. Vertebrate taphonomy. Cambridge: Cambridge University Press, 1994. When studying the past it is important to gain contextual information in order to have a solid understanding of the data. Often these findings can be used to better understand cultural or environmental shifts within the present day. The term taphomorph is used to collectively describe fossil structures that represent poorly-preserved and deteriorated remains of various taxonomic groups, rather than of a single species. For example, the 579–560 million year old fossil
Ediacaran The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and t ...
assemblages from
Avalonia Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, southern Ireland, and the eastern coast of North America. It is the source of many of the older rocks of West ...
n locations in
Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...
contain taphomorphs of a mixture of
taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...
which have collectively been named Ivesheadiomorphs. Originally interpreted as fossils of a single genus, ''Ivesheadia'', they are now thought to be the deteriorated remains of various types of frondose organism. Similarly, Ediacaran fossils from England, once assigned to ''Blackbrookia'', ''Pseudovendia'' and ''Shepshedia'', are now all regarded as taphomorphs related to
Charnia ''Charnia'' is a genus of frond-like lifeforms belonging to the Ediacaran biota with segmented, leaf-like ridges branching alternately to the right and left from a zig-zag medial suture (thus exhibiting glide reflection, or opposite isometry). T ...
or
Charniodiscus ''Charniodiscus'' is an Ediacaran fossil that in life was probably a stationary filter feeder that lived anchored to a sandy sea bed. The organism had a holdfast, stalk and frond. The holdfast was bulbous shaped, and the stalk was flexible. The ...
.


Fluvial taphonomy

Fluvial taphonomy is concerned with the decomposition of organisms in rivers. An organism may sink or float within a river, it may also be carried by the current near the surface of the river or near it's bottom. Organisms in terrestrial and fluvial environments will not undergo the same processes. A fluvial environment may be colder than a terrestrial environment. The ecosystem of live organisms that scavenge on the organism in question and the abiotic items in rivers will differ than on land. Organisms within a river may also be physically transported by the flow of the river. The flow of the river can additionally erode the surface of the organisms found within it. The processes an organism may undergo in a fluvial environment will result in a slower rate of decomposition within a river compared to on land.


See also

*
Beecher's Trilobite type preservation The preservational regime of Beecher's Trilobite Bed (Upper Ordovician) and other similar localities involves the replacement of soft tissues with pyrite, producing a three-dimensional fossil replicating the anatomy of the original organism. Only ...
* Bitter Springs type preservation *
Burgess Shale type preservation The Burgess Shale of British Columbia is famous for its exceptional preservation of mid-Cambrian organisms. Around 69 other sites have been discovered of a similar age, with soft tissues preserved in a similar, though not identical, fashion. Addit ...
* Doushantuo type preservation *
Ediacaran type preservation Ediacaran type preservation relates to the dominant preservational mode in the Ediacaran period, where Ediacaran organisms were preserved as casts on the surface of microbial mats. Exceptional preservation All but the smallest fraction of the ...
*
Fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
*
Karen Chin Karen Chin is an American paleontology, paleontologist and taphonomy, taphonomist who is considered one of the world's leading experts in coprolites. Biography Chin loved studying living things as a child, and enjoyed memorizing the names of spe ...
*
Lagerstätte A Lagerstätte (, from '' Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These f ...
* Permineralization * Petrifaction * Pseudofossil * Trace fossil


References


Further reading

* *Greenwood, D. R. (1991), "The taphonomy of plant macrofossils". In, Donovan, S. K. (Ed.), ''The processes of fossilisation'', p. 141–169. Belhaven Press. *Lyman, R. L. (1994), ''Vertebrate Taphonomy.'' Cambridge University Press. *Shipman, P. (1981), ''Life history of a fossil: An introduction to taphonomy and paleoecology''. Harvard University Press. *


External links

* Th
Shelf and Slope Experimental Taphonomy Initiative
is the first long-term large-scale deployment and re-collection of organism remains on the sea floor.
''Journal of Taphonomy''


at the College of Wooster
Comprehensive bioerosion bibliography
compiled by Mark A. Wilson


Minerals and the Origins of Life
( Robert Hazen,
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...
) (video, 60m, April 2014).
7th International Meeting on Taphonomy and Fossilization
(Taphos 2014), at the Università degli studi di Ferrara, Italy, 10–13 September 2014 {{Authority control Archaeological science Methods in archaeology