All of the Following Are Taphonomic Processes Except

Anthropology/Odontology

T. Simmons , P.A. Cross , in Encyclopedia of Forensic Sciences (Second Edition), 2013

Introduction

Forensic taphonomy is a rapidly developing field within forensic anthropology and forensic archeology. Research in forensic taphonomy encompasses refining estimates of time since death in various scenarios, differentiating peri- and postmortem trauma, identifying the effects of burning, understanding the directionality of impact in blunt force and projectile trauma in various skeletal elements, reassociating individuals commingled in secondary mass graves or explosions, weathering of bones and teeth, and an extended range of related topics.

Although taphonomy itself has a relatively long history in the paleontological and archeological literature, forensic taphonomy is a comparatively new discipline, developing in response to the demands of casework and to the various circumstances in which bodies are found.

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Zooarcheology

Steve Wolverton , Lisa Nagaoka , in Ethnozoology, 2018

Taphonomic Analysis

Taphonomy is the study of the transition of organic matter from the biosphere to the lithosphere, and the word literally means "burial studies" (see Lyman, 1994 for thorough discussion; see Broughton and Miller, 2016 for a basic summary). Zooarcheologsts and paleontologists recognize that this transition can involve a substantial variety of processes and effects that relate to an array of taphonomic agents. Such processes can be additive—meaning that signatures of processes, such as weathering, butchery, or animal gnawing (e.g., rodent or carnivore), might be left on bone—telling the zooarcheologist about the history of taphonomic damage after the animal died and prior to excavation. Alternatively, taphonomic agents can be subtractive; for example, gnawing and digestion of bone by carnivores can destroy portions of skeletal elements or complete bones. The magnitude of such damage varies among species of carnivores and may even differ within the same species depending on environmental and behavioral settings [e.g., how productive the environment is or how hungry the carnivore is; see Nagaoka (2015)].

The taphonomist—in this case the zooarcheologist who is studying the taphonomy of remains from an archeological site—is writing a detailed narrative (a taphonomic history) of the processes that influenced the skeletal and taxonomic composition of the remains she/he is studying. In some cases, taphonomists are able to apply general rules of thumb. For example, zooarcheologists can easily determine whether or not a faunal assemblage was influenced by "density mediated destruction" of remains. In such cases, low-density (and thus less robust) bones and parts of bone are of lower abundance or are absent compared to portions and elements that are higher density (more robust). A number of processes can lead to differential destruction of low-density portions and elements, such as animal gnaw damage, weathering, and even hydrological transport, which produces separate lag and transported deposits. Similarly, the shape of skeletal (or exoskeletal) elements can influence whether or not destruction or preservation occurs (Darwent and Lyman, 2002).

In other cases, the taphonomic history of an assemblage may be quite unique, related either to exceptional preservation or destruction conditions. For example, natural trap caves may attract and accumulate high numbers of carnivores (and their remains), compared to midden deposits near prehistoric villages and camps. If a carnivore is trapped in a cave but survives for a period of time, it is likely that any previously deposited animal remains will be extensively gnawed. In contrast, animal remains deposited in trash middens near archeological sites, may or may not have attracted carnivores, but may also have been differentially exposed to weathering from wind, precipitation, and soil conditions. If people cooked meat without removing bones, or if bones were smashed to increase surface area for processing within-bone nutrients, such as grease, then yet a different taphonomic narrative will emerge during analysis.

Correspondingly, taphonomy is an iterative process that balances the study of what are known to be general, identifiable effects with the unique historical contingencies of animal death, butchery, transport, consumption, discard, burial, and preservation. Identifiable taphonomic effects might include marks from hammering and fracturing bone to remove marrow or carnivore tooth marks from gnawing. However, the degree to which each (or any other taphonomic agent) influences the character of a zooarcheological assemblage of remains depends on the cultural and environmental setting—or the configuration—of the taphonomic history. Striking this iterative balance is intimately related to assessing data quality because studying the taphonomic history of one or another assemblage of animal remains may lead to the conclusion that it is useful for answering one type of archeological research question but not others. Because taphonomic histories of faunal assemblages influence what a particular dataset represents about prehistory, it is important to make conservative statistical assumptions when quantifying zooarcheological remains.

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Why Are Bryophytes So Rare in the Fossil Record? A Spotlight on Taphonomy and Fossil Preservation

Alexandru M.F. Tomescu , ... Adolfina Savoretti , in Transformative Paleobotany, 2018

3.5 A Taphonomic Summary of Bryophyte Fossilization

Could taphonomy introduce sufficient bias to account for the significant disparity between the bryophyte and the vascular plant fossil record? Looking at bryophyte fossilization as a chain of interconnected events ( Fig. 16.3), we summarize the topics discussed up to this point.

Figure 16.3. Overview of taphonomic pathway, taphonomic factors, and extrataphonomic factors with potential to influence the structure of the bryophyte fossil record. See also Sections 3.1–3.3, 3.5, and 4 in the text.

Necrology can be expected to introduce significant bias because bryophytes make fewer biomass available for fossilization via physiological loss compared with vascular plants. Although many bryophytes produce vegetative propagules, these are minute and, if found dispersed, are less likely to be recognized (see Section 3.1). Moreover, the small size and low, ground-hugging stature of bryophytes make traumatic removal of whole plants or plant parts less effective in producing material that enters the taphonomic pathways responsible for the formation of the majority of plant fossils. These same factors, by contrast, greatly increase the chances for preservation of complete plants or even entire populations via in situ burial during sudden depositional events. While in situ burial is more common among bryophytes compared with vascular plants, overall, bryophytes seem somewhat less likely to enter taphonomic pathways (i.e., by removal from their growth environment).

Biostratinomic processes act, in general, similarly, on bryophyte material as they do on vascular plant material. Considering transport, however, a major source of bias against the preservation of bryophyte material could be its small size. Fossilization potential decreases exponentially with decreasing particle size, because (1) the smaller the particle, the longer the time it will spend in suspension during transport, exposed to degrading agents; and (2) the smaller the particle, the narrower the time window during which it is potentially available for fossilization, as the smaller it gets, the faster it will be obliterated by physical (abrasion, fragmentation), biological (microbial decay), and chemical degrading factors. As a consequence, the retention times during which small bryophyte material remains potentially available for fossilization may sometimes be too short to be compatible with the time scales at which the sedimentological processes of transport, deposition, and burial normally operate.

Thus, bryophyte material appears more likely to be obliterated via biostratinomic porcesses than vascular plant material, given equal intensity of degradation or exposure time. Furthermore, the smaller, lighter bryophyte particles are more likely to be resuspended by currents, which delays burial even longer. In this context, fossilization of bryophytes (and, likewise, of similarly, sized vascular plant particles, such as small flowers) should, therefore, depend much more on extraordinary sedimentary processes, such as sudden high-energy depositional events, compared with fossilization of larger vascular plant material. Nevertheless, expectations of rapid degradation of bryophyte material during transport are at odds with the richness of some bryophyte floras documented in allochthonous assemblages from marine strata (see Section 3.2), which demonstrate that long-distance transport does not preclude preservation of small bryophyte particles in large quantities and with outstanding quality of preservation. Consequently, while theoretical considerations suggest that transport should introduce a taphonomic bias in bryophyte fossilization, the currently available data most relevant to transport effects suggest that the latter may not be very consequential, and make it difficult to assess the magnitude of the bias introduced by transport in bryophyte fossilization.

Burial, which insulates the plant material from degrading factors, favors bryophytes because they are smaller than most vascular plant material and, thus, require less sediment (and shorter time) to be buried, under similar sedimentation regimens. However, in clastic deposits, the bryophyte material, characterized by diagnostic characters that are resolved at very small scales, is more sensitive than vascular plant parts to the grain size of the host rock, in terms of taxonomic resolution; the latter is positively correlated with the fidelity of preservation of diagnostic characters, which, in turn, is inversely correlated with grain size of the host rock (see Section 3.2). Overall, burial factors are not expected to bias the bryophyte fossil record significantly, compared with that of vascular plants, except, maybe, in coarser clastic deposits.

Finally, given the comparable mechanical and chemical resilience of bryophyte and vascular plant tissues, diagenetic processes are not expected to introduce significant bias in the fossil record. However, in terms of weathering of fossiliferous rocks in exposures, the overall smaller size of bryophyte fossils, again, leaves a narrower time window for discovery before weathering and erosion obliterate a fossil.

In conclusion, if bryophytes are at least as old as vascular plants and equally tough (see Section 2), the differences we see should be due in part to a "pre-taphonomic bias," namely the fact that bryophytes are less prone to enter typical taphonomic pathways, in the first place. This may reflect a combination of morphological constraints (small size, substrate-hugging growth habit) and the specifics of bryophyte ecology and population geography—occurrence in more strictly circumscribed and patchier environments (albeit ubiquitous and cosmopolitan) than vascular plants. In addition, we suggest a key factor affecting the taphonomy of bryophytes relates to necrology, with bryophytes making proportionally smaller amounts of biomass available for fossilization via physiological loss, compared with tracheophytes. It is less clear whether biostratinomic factors have the potential to bias the bryophyte fossil record, with the typically smaller particle size of bryophyte material skewing the fossil record toward a lower quantity. In any case, the bryophyte potential for exquisite preservation is demonstrated by numerous fossil occurrences. Nonetheless, we suspect that human bias may have played just as important a role in shaping the current state of the bryophyte fossil record.

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Early Hominin Ecology

Jeanne Sept , in Basics in Human Evolution, 2015

Site Taphonomy

The science of analyzing the fossilization process is called "taphonomy" ( Behrensmeyer, 1984). In particular, for paleoecological interpretation it is important to determine whether evidence was buried close to where a hominin lived or died (in a primary context) or transported before burial or disturbed and reburied (in a secondary context). For example, the location of a near-complete H. erectus (see the chapter by Simpson) skeleton like the "Turkana Boy" (discovered at the Nariokotome site near Lake Turkana, Kenya) can be examined to learn the circumstances of death; as interpreted by the research team of Alan Walker, over 1.5 mya this adolescent boy died in the seasonally marshy floodplain of a large river, and his body then floated and decomposed gently in the wetlands, where it became naturally buried in fine-grained sediments (Walker and Leakey, 1993). This type of primary geological context at Nariokotome contrasts markedly with nearby examples of hominin fossils in the secondary context. In the paleochannel deposits of the same large river, a number of individual fossil teeth of contemporary robust australopithecines have been recovered; these isolated fossil teeth had been transported like pebbles downstream in the swiftly moving current. But unlike the Turkana Boy, who had died in the flat floodplains near the river, these australopithecines had died somewhere upstream, perhaps as much as 50   km away in a very different habitat, and their skeletons had become broken up and disarticulated with only the most durable remnants coming to rest in sandy gravel bars downstream (Behrensmeyer and Reed, 2013).

Information about site formation processes can also be gleaned from the fossils and artifacts themselves. For example, the first australopithecine fossil discovered, the "Taung Child," was recognized almost a century ago in South Africa by Raymond Dart. Dart chiseled the fossil out of an encasing block of breccia—calcium carbonate deposits that had cemented the little skull in cave sediments millions of years ago. Dart thought that the child had probably lived and died in the cave in which it had become buried, and assumed that the australopithecine's environment was much like the open grasslands that surround the site today. Later, examining the bones of more australopithecines and other savanna animals found in other South African caves, Dart even suggested that early hominins could only have survived in such demanding environments if they had been both tool users and meat eaters; he argued that the broken bones of other large animals found in the South African caves had been the prey of the australopithecines. However, more recent studies of bone surface damage patterns to the Taung Child (Berger and McGraw, 2007) and dental microwear of other primate fossils from the site (L'Engle Williams and Patterson, 2010) lead to different paleoecological conclusions; skull damage suggests that the child had been captured and eaten by a large predatory bird, and its remains dribbled onto the ground, where they ultimately got washed into an underground cavern. In subsequent taphonomic studies of other South African cave deposits (Brain, 1981, 1993), C.K. Brain has demonstrated that most of the bones in these caves, including those of the australopithecines, were the remains of killings by carnivores such as leopards and hyenas—these hominins were the most likely prey rather than predators, raising interesting questions about the adaptations and ecology of different australopithecine species.

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PATTERNED THERMAL DESTRUCTION OF HUMAN REMAINS IN A FORENSIC SETTING

STEVEN A. SYMES Ph.D., D.A.B.F.A. , ... ANDREA L. PIPER B.A. , in The Analysis of Burned Human Remains, 2008

THE CONCEPTS OF 'PERIMORTEM' AND 'POSTMORTEM' IN BONE TRAUMA

While anthropologists attempt to ascribe a perimortem or postmortem temporal classification in skeletal traumatic interpretations, the timing of the defect in relation to the moment of death is the most perplexing objective of trauma and taphonomy analysis. Accordingly, this classification relies almost entirely on the determination of whether a defect occurred when the bone was fresh, or dry and degraded. After death, the biochemical composition of bone changes with time, especially in terms of the amount and preservation of its organic matrix. From a biomechanical point of view, the main consequence of these changes is a reduction in the elasticity of bone materials, in transition from fresh (perimortem) to dry (postmortem/taphonomic), classic anthropological bone categories.

This results in a temporal discrepancy between the concepts of antemortem, perimortem, and postmortem (taphonomic), when anthropologists consult with pathologists in medicolegal settings. Antemortem occurs before death, or more specifically long enough before death to allow for an identifiable vital reaction from the living tissue. The concepts of perimortem and postmortem, however, are not so easily delineated by the medical and anthropological communities. In the case of sharp force trauma examination, an anthropologist's assessment of a dismemberment case is performed essentially within the theoretical perimortem context, as the skeletal material will retain nearly all the same properties as it showed in life (Symes et al., 2002). On the other hand, the dismemberment of a body before death clearly would be an unusual circumstance and medical personnel would likely assume the cut marks were created postmortem.

Hence, anthropologists must consider skeletal trauma primarily in a taphonomic context. Defects occurring in bone must be excluded as taphonomic in nature before they can be considered to have occurred in the perimortem interval. While careful taphonomic interpretations can reveal information concerning circumstances surrounding death and postmortem interval (Dirkmaat and Adovasio, 1997), perimortem trauma interpretation can lead directly to a forensic anthropologist aiding the forensic pathologist in determinations of cause and manner of death. Thus, 'accurate and conservative interpretation of contextual taphonomic data ultimately reduces confusion by simplifying key variables … regarding cause and manner of death' (Symes et al., 2002:405).

Burned bone trauma further confuses this temporally sensitive issue. There are a number of circumstances in which fire trauma (though not to bone) may be directly related to the cause (e.g., smoke inhalation/asphyxia) and manner (e.g., homicide, accidental) of death and should be considered in the perimortem interval. If the thermal damage were to compromise bone (certainly, after death), medical personnel would consider this postmortem trauma. Although thermal damage and sharp force trauma derived from dismemberment or mutilation would conceivably be inflicted to bone in similar timeframes after death (anthropologically perimortem), the intense heat and subsequent drying of bone would result in bone fractures that would appear postmortem from a biomechanical point of view. This anthropological 'impression' of perimortem versus postmortem and wet versus dry lies within the rudimentary properties of bone itself. As bone degrades, it responds to forces in identifiably different manners. Herein lies the importance of applying burn pattern and process signature recognition to burned bone analysis.

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The Fossil Record

John G. Fleagle , in Primate Adaptation and Evolution (Third Edition), 2013

Reconstructing Behavior

Generally, the best and most reliable information about the habits of an extinct primate is obtained by comparing details of its dental and skeletal anatomy with those of living primates. Sediments may tell us where it died, and taphonomy may tell us how and why it was preserved, but its teeth and bones can tell us how it lived – what it ate, how it moved, and possibly in what kind of social group it lived. In the previous chapter we discussed many of the associations between behavior and anatomy among living primates that form the basis for our interpretations of fossil behavior. Our ability to reconstruct the habits of an extinct primate from its bones is intimately linked to our understanding of how the shape of bones in living primates varies with their behavior. Associations between bony morphology and behavior that are true among living primates only 'some of the time' cannot be expected to yield reliable reconstructions when applied to fossils (see Ross et al., 2002).

Furthermore, we have to remain always aware that uniformitarianism has its limits: the present is our best key to the past, but the past was not necessarily just like the present. We know, for example, that tooth size and many aspects of behavior are highly correlated with body size among living primates, but we cannot necessarily extrapolate these relationships based on a finite sample of living species to a fossil primate whose teeth are considerably larger or smaller than those of any living species. Likewise, many fossil primates had anatomical features that were quite different from anything we find among living species. We are sure to have problems interpreting such structures, and may need to compare the fossil primates with another type of mammal for an analogy.

We commonly find that fossil primates differ from living species in the combinations of anatomical features they exhibit. A fossil ape may have a humerus that resembles that of a howling monkey in some features, that of a variegated lemur in others, and that of a macaque in still others. In such a case we must examine closely the mechanical implications of the individual features rather than simply look for a living species that matches the fossil in all respects. Our reconstructions of the behavior of extinct primates from their bones and teeth must be based not on simple analogy, but on an understanding of the physiological and mechanical principles underlying the associations between bony structure and behavior. (Ross et al., 2002).

Just as stable isotopes can be used as a tool to help reconstruct paleoenvironments, they can also provide many insights into the behavior of extinct animals, especially regarding their diet (Cerling et al., 2011; Crowley, 2012). For example, the ratio of carbon isotopes in the teeth of both fossil and living mammals is be correlated with the chemical composition of their diet. Thus, it is possible to distinguish species that ate predominantly plants using a C₃ photosynthetic pathway (most trees and herbs) from those that ate predominantly plants using a C₄ pathway (grasses and many tubers) (Sponheimer and Lee-Thorp, 2007). Nitrogen isotopes can distinguish carnivores from herbivores because the ratio of ¹⁵N to ¹⁴N increases with every step of the food chain, so that herbivores have higher values than plants and carnivores have higher values than herbivores. Other isotopes can help distinguish animals living in closed habitats from those in open habitats (e.g., Schoeninger et al., 1999; Loudon et al., 2007).

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Plant Macrofossil Introduction☆

H.H. Birks , in Reference Module in Earth Systems and Environmental Sciences, 2017

Abstract

This article provides an introduction to plant macrofossil analysis and an overview of the articles in this subsection. A plant macrofossil can be defined as a plant fossil that is visible to the naked eye and that can be manipulated by hand. There are short accounts of where macrofossils can be found, how they are sampled and analyzed, their taphonomy, and how they represent the vegetation that produced them. Macrofossil types of particular palaeoecological interest are illustrated by photographs. Examples are discussed of the contributions made by macrofossil studies to aspects of Quaternary palaeoecology, such as vegetation history and situations where they greatly enhance interpretations from pollen analysis. Their application in accelerator mass spectrometry radiocarbon dating is summarized, including high-resolution chronologies, avoidance and correction of lake and marine reservoir ages, and dating of tephras as time markers, as well as their use in reconstructing past atmospheric carbon dioxide (CO ₂) concentrations from fossil leaves, and their combination with the analysis of ancient DNA.

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Evolution of the Primate Brain

Christoph P.E. Zollikofer , in Progress in Brain Research, 2012

Reconstructing fossil hominin cranial ontogenies

Comparison of modern human and chimpanzee cranial ontogenies leads to three evolutionary questions: When did the proposed ontogenetic modifications occur during hominin evolution? How was craniomandibular ontogeny modified? Which selective pressures favored these modifications? Studying craniomandibular ontogeny in fossil hominin species faces several challenges. Fossilized hominin remains are deteriorated, fragmented, and distorted by processes of taphonomy and diagenesis. Moreover, immature skeletal elements are often unfused, adding further difficulties to the reconstruction of a specimen's morphology at the time of death. Computer-assisted paleoanthropology provides a set of methods to efficiently tackle these problems ( Zollikofer and Ponce de León, 2005). Following non-invasive 3D data acquisition with computed tomography, computer graphics tools are used to prepare specimens non-invasively, correct the effects of taphonomic deformation, recompose their three-dimensional morphology on the computer screen, and complement missing regions via mirror-imaging and/or interpolation/extrapolation. These virtual skulls can then be submitted to morphometric analysis.

A further challenge is to evaluate the individual age of immature fossil specimens. As mentioned, teeth (if present) are routinely used as absolute and relative age indicators. Synchrotron-based dental microstructural analysis now permits age-at-death estimates of fossil hominins with an error range of a few weeks (Tafforeau and Smith, 2008; Tafforeau et al., 2006).

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Anthropology/Odontology

D. Franklin , M.K. Marks , in Encyclopedia of Forensic Sciences (Second Edition), 2013

Method Selection

The majority of evaluations are successful through examination of gross morphological features, attainable with complete or substantial portions of diagnostic surface bone. The loss of diagnostic features and degree of fragmentation or cortical damage, loss, or weathering will determine the appropriate analytical method, for example, histological or molecular. Very often, method choice is linked to the cause and/or manner of death and/or postmortem taphonomy.

Another crucial aspect during gross evaluation is the biological age of the victim. Subadult bones, especially fetal and perinate, often bear faint resemblance to their adult counterparts and are frequently dismissed as nonhuman. Hence, it is imperative that the observer has a thorough and comprehensive understanding of the structural appearance of human skeletal and dental elements at all stages of growth. Such knowledge is assimilated after years of training and 'hands-on' experience, and although textbooks on juvenile osteology are an invaluable source, in isolation they do not provide sufficient demonstrations of the morphological complexities of nonadult bone.

For secure identifications when isolated fragments or calcined or cremated remains are discovered, assessing human or nonhuman origin will require either a histological approach in quantifying patterned cellular differences or immunological tests and DNA analysis at the molecular level. These methods too have their inherent shortcomings that limit their widespread utilization, including young age with the appearance of plexiform bone, sex, pathology, for example, osteoporosis affecting cortical bone, diagenesis obliterating structural arrangement, contamination, and diverse results from sampling design. Irrespective of all this, these nonmorphological methods require appropriate expertise and specialized laboratory equipment. To this end, there need to be some a priori inference that human remains are potentially involved.

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The Geological Succession of Primary Producers in the Oceans

ANDREW H. KNOLL , ... JOHN E. ZUMBERGE , in Evolution of Primary Producers in the Sea, 2007

A Prokaryotic Fossils

By the earliest Proterozoic Eon, cyanobacteria must have been important contributors to primary production—there is no other plausible source for the O₂ that began to accumulate in the atmosphere and surface oceans 2.45−2.32 billion years ago (Ga). Consistent with this observation, it has been appreciated since the early days of Precambrian paleontology that cyanobacteria-like microfossils are abundant and widespread constituents of Proterozoic fossil assemblages (Figure 8; Schopf 1968 ). Not all cyanobacteria have diagnostic morphologies, but some do and others are likely candidates for attribution given knowledge of taphonomy (processes of preservation) and depositional environments represented in the record. By mid-Proterozoic times, if not earlier, all major clades of cyanobacteria existed in marine and near-shore terrestrial environments, including those that differentiate akinetes and heterocysts (Tomitani et al. 2006). The best-characterized Proterozoic cyan-obacteria come from early diagenetic chert nodules in carbonate successions (e.g., Schopf 1968; Zhang 1981; Knoll et al. 1991; Sergeev et al. 1995, 2002; Golubic and Seong-Joo 1999). These fossils are largely benthic and largely coastal marine. Stromatolites, however, indicate a much wider distribution of benthic cyanobacteria in the photic zone. (A role for cyanobacteria or of organisms in general is difficult to establish in the precipitated stromatolites found in Earth's oldest well-preserved sedimentary successions; however, the likelihood that cyanobacteria were major architects of Proterozoic stromatolites that accreted primarily by trapping and binding is high) (Grotzinger and Knoll 1999). Microfossils are less useful for evaluating the contributions of cyanobacteria to the phytoplankton of Proterozoic oceans because many were small, nondescript, and likely to settle on the seafloor in places where interpretable preservation was improbable. Given the distribution of planktonic clades on a phylogenetic tree calibrated by well-documented fossils, however, it is likely that cyanobacteria were important constituents of the phytoplankton in Proterozoic oceans (Sanchez-Baracaldo et al. 2005; Tomitani et al.2006; see later).

FIGURE 8. Cyanobacteria in Proterozoic sedimentary rocks. (A) 700−800-million-year-old endolithic pleurcapsalean fossil. (B) 1500-million-year-old mat building cyanobacterium closely related to modern Entophysalis. (C) 1500-million-year-old short trichome. (D) Spirulina-like fossil in latest Proterozoic (<600 Ma) phosphorite. Scale bar = 15 microns in (A-C), and = 25 microns in (D).

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All of the Following Are Taphonomic Processes Except

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