This means their chemical composition has changed in the process of fossilisation.
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ONE OF the core tenets of fossilisation is that hard material preserves more readily than the soft stuff.
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The skull had been crushed during the fossilisation process, so scientists used a CT scanner to help virtually reconstruct a complete image.
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Unfortunately, the embryos are all incomplete and disarticulated, meaning the bones have been jumbled during fossilisation rather than preserved in a nice jointed skeleton.
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Fossils of social wasps are rare in the fossil record, probably due to behavioural characteristics and paper nest structures that do not lend themselves to fossilisation.
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The appearance of limited fossilisation initially led the explorers to think the bones were from the last caver into the chamber, who had subsequently never made it back out alive.
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In addition, adult learners living in a foreign country may not have very high linguistic demands placed on them, for example if they are a low-level employee at a company. Without the incentive to develop high-level skills in their second language, learners may undergo language fossilisation, or a plateau in their language level. Classroom instruction can be useful in both providing appropriate input for second-language learners, and for helping them overcome problems of fossilisation.
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The fossil, in the end, consists of a thin layer of pure carbon or its mineralized form, graphite. This form of fossilisation is called carbonisation. It is particularly important for plant fossils.Levin (1987), pp.
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No postcranial remains have been recovered. The only known skull suffered a large amount of distortion during the time of fossilisation and discovery, as the cranium is dorsoventrally flattened, and the right side is depressed.
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The ectocochleate (externally shelled) cephalopods are the oldest known representatives of their class, dating back to the Cambrian period. Their aragonitic shells are not prone to fossilisation. They contain the modern Nautilus and many fossil forms including the ancient Ellesmerocerida and the ammonoids.
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Fossil records of Myxogastria are extremely rare. Due to their short lifespan and the fragile structures of the plasmodia and the fruit body, fossilisation and similar processes are not possible. Only their spores can be mineralised. The few known examples of fossilised living states are preserved in amber.
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Paris Miguirditchian, Julie (2010) "Artist in the flow". Digitalarti Mag Mufson, Beckett (15 May 2015) "Here Are Imaginary Fossils from a Post-Human Earth". The Creators Project Murphy, Jay (2009) "A fiction without narration", thing.net Palmiéri, Christine (2013) "Fossilisation du futur", Archée Popper, Frank (2006) From Technological to Virtual Art.
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Enamel can be lost by abrasion or spalling, and is lost before dentine or bone are destroyed by the fossilisation process. In such a case, the 'skeleton' of the teeth would consist of the dentine, with a hollow pulp cavity. The organic part of dentine, conversely, is destroyed by alkalis.
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Additionally, remains were identified of the egg membrane, the membrana testacea. The fibres of the membrane are individually visible and have a length of 1.5 to 4 micrometres. They possibly contain part of the original proteins. It is likely that during fossilisation, the egg shells shifted in relation to each other and were otherwise distorted.
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He is said not to have reached full size, dying as a mature adolescent and that the process of his fossilisation was so perfect it preserved even the injuries and diseases he sustained in his lifetime including -amongst others- lumps where his ribs healed after their break and the raging infection on his middle toe.
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In Extinction Event, in an area where live specimens of Cretaceous life forms have been collected, Cutter stops to look at a tiny crested bird in a wire cage that was captured by the Russian team. One of the men describes how rare this actually is, as tiny-boned creatures rarely remain intact in fossilisation.
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Ticks (Ixodida) are parasitic arachnids, typically 3 to 5 mm long, part of the superorder Parasitiformes. Along with mites, they constitute the subclass Acari. Ticks are external parasites, living by feeding on the blood of mammals, birds, and sometimes reptiles and amphibians. Ticks evolved by the Cretaceous period, the most common form of fossilisation being amber immersion.
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This Marrella specimen illustrates how clear and detailed the fossils from the Burgess Shale lagerstätte are. Fossils of organisms' bodies are usually the most informative type of evidence. The most common types are wood, bones, and shells. Fossilisation is a rare event, and most fossils are destroyed by erosion or metamorphism before they can be observed.
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Waptia fieldensis had a maximum body length of . The exoskeleton was very thin and easily distorted from fossilisation. It possessed a large bivalved carapace that was narrow at the front with wide posterior margins that covered the cephalon and most of the thorax. The cephalon had five short somites (body segments) with three to five pairs of small and poorly preserved feeding appendages.
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One possibility is that the absence of bioturbation permitted the fossilisation, but some Burgess Shale fossils contain internal burrows, so that can't be the whole story. It is possible that certain clay minerals played a role in this process by inhibiting bacterial decay. Alternatively, reduced sediment permeability (a result of lower bioturbation rates and abundant clays) may have played a role by limiting the diffusion of oxygen.
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The rare conditions that allowed for the fossilisation of pterosaur remains, sometimes also preserved soft tissues. Modern synchrotron or ultraviolet light photography has revealed many traces not visible to the naked eye. These are often imprecisely called "impressions" but mostly consist of petrifications, natural casts and transformations of the original material. They may include horn crests, beaks or claw sheaths as well as the various flight membranes.
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Restoration of P. sibiricus Seventeen species have been referred to the genus Psittacosaurus, although only nine to eleven are considered valid today. This is the highest number of valid species currently assigned to any single dinosaur genus (not including birds). In contrast, most other dinosaur genera are monospecific, containing only a single known species. The difference is most likely due to artifacts of the fossilisation process.
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Scipionyx is considered one of the most important fossil vertebrates ever discovered, after a long and painstaking "autopsy" revealed the unique fossilisation of portions of its internal organs. It is believed Scipionyx lived in a region filled with shallow lagoons. These bodies of water were oxygen deficient, leading to the well-preserved Scipionyx specimen, much like the fine fossil preservation seen in Germany's Archaeopteryx.Reisdorf, A.G., and Wuttke, M. (2012).
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However, the most parsimonious explanation is that the rock was deposited during the fossilisation process after TM 1517 had died. In 1961, science writer Robert Ardrey noted two small holes about 2.5 cm (an inch) apart on the child skullcap SK 54, and believed this individual had been killed by being struck twice on the head in an assault; in 1970, Brain reinterpreted this as evidence of a leopard attack.
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Parsons holds a European Research Council Consolidator Award and is also a Division President of the European Geosciences Union. Parsons also researches the leakage and transport of plastics in rivers, coasts and estuaries and as part of the Huxley debate at the 2018 British Science Festival he claimed that the most significant marker for the Anthropocene age may be the fossilisation of plastic debris such as formed in plastiglomerate.
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The examination under UV revealed a more extensive covering of filament-like structures, similar in anatomy to the primitive feathers of other compsognathids, including Sinosauropteryx. The investigation also discovered additional patches of soft tissue, on the snout and the lower leg, and vertical collagen fibres between the chevrons of the tail vertebrae. Achim Reisdorf and Michael Wuttke in 2012 described the taphonomical circumstances of the fossilisation of the holotype of Juravenator starki. Foth et al.
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The late occurrence of pachycephalosaurs compared to the related ceratopsians indicates a long ghost lineage (inferred, but missing from the fossil record) spanning 66 million years, from the Late Jurassic to the Cretaceous. Since pachycephalosaurs were mainly small, this may be due to taphonomic bias; smaller animals are less likely to be preserved through fossilisation. More delicate bones are also less likely to be preserved, which is why pachycephalosaurs are mainly known from their robust skulls.
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Reconstruction of Phacops with a speculative, cryptic "Rorschach" pattern based on the proposed ability to camouflage. There are specimens known of Phacops rana with many irregular black spots. Because similar spots in a specimen of Greenops boothi from the same site are arranged in rows, it may be assumed that they are original and not caused by the fossilisation process. The spots are irregular and have spurs branching outwardly, similar to the melanophores in many extant animals.
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One of the larger members of the Canadian Arctic Archipelago, it is also a member of the Sverdrup Islands and Queen Elizabeth Islands. It is known for its unusual fossil forests, which date from the Eocene period. Owing to the lack of mineralization in many of the forest specimens, the traditional characterization of "fossilisation" fails for these forests and "mummification" may be a clearer description. The fossil records provide strong evidence that the Axel Heiberg forest was a high-latitude wetland forest.
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Scanella and Horner recognised that not all data were easily explained by their hypothesis. For these they advanced auxiliary hypotheses. One problem was that if Torosaurus were the normal last maturation phase of Triceratops, which phase they called the "toromorph", it would be expected that Torosaurus fossils were quite common, whereas in fact they are rather rare. This they explained by a high mortality of subadults and the possibility that old animals preferentially lived on heights, where erosion prevented fossilisation.
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Fossil-rich layers in a sedimentary rock, Año Nuevo State Reserve, California Among the three major types of rock, fossils are most commonly found in sedimentary rock. Unlike most igneous and metamorphic rocks, sedimentary rocks form at temperatures and pressures that do not destroy fossil remnants. Often these fossils may only be visible under magnification. Dead organisms in nature are usually quickly removed by scavengers, bacteria, rotting and erosion, but sedimentation can contribute to exceptional circumstances where these natural processes are unable to work, causing fossilisation.
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The taphonomy (burial and fossilisation process) of the three main Plateosaurus sites—Trossingen, Halberstadt and Frick—is unusual in several ways. All three sites are nearly monospecific assemblages, meaning that they contain practically only one species, which requires very special circumstances. However, shed teeth of theropods have been found at all three sites, as well as remains of the early turtle Proganochelys. Additionally, a partial "prosauropod" skeleton was found in Halberstadt that does not belong to Plateosaurus, but is preserved in a similar position.
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The posterior thoracic group is made up of six somites, each possessing a pair of long multi-jointed appendages. The segments of these appendages are longer near the body and taper towards the flexible distal segments, extending past the carapace. They bear a fringe of long, slender filaments, all of which are directed towards the middle of the body, a characteristic shared by extant crustaceans. Though usually squashed into blade-like shapes from the fossilisation process, the filaments were slender cylindrical tubes when the animal was alive.
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It was inferred that all dinosaurs had such complex tongue bones but that these were generally lost during fossilisation. Metacarpus of a juvenile specimen Life reconstruction of a Pinacosaurus by Jack Mayer Wood The postcranial skeleton of the known fossils is rather lightly built. Most of these represent juveniles, however: even specimen IMM 96BM3/1, the P. mephistocephalus holotype, is no longer than about . Juveniles had four rear back vertebrae fused into a "sacral rod", three true sacrals, and a tail base of seven vertebrae possessing transverse processes.
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The indigenous theatre, which in most cases remained a part of the rural culture, has failed to meet the demands of the 21st century life in Bangladesh and a process of fossilisation has already set in. On the other hand, the European theatre has been dynamic because the elite urban intelligentsia, who have been responding to the needs of urban spectators, have sustained it. Inception of the European theatre in Bangladesh or erstwhile East Bengal took place in 1855 with a performance of Svarna Sharnkhal by Durgadas Kar at Barisal.
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Thalassina anomala - Fossil Fossils of Thalassina are encountered "in countless numbers", and extend back as far as the Miocene. They are generally preserved in a hard phosphatic nodule which is believed to be the animal's moulting position. Storms may trap the animals in their burrows, and the mineral-rich nature of the sediments leads to very rapid fossilisation. The presence of Thalassina, together with other warm-water species in the Miocene of Japan (outside the current range of the species) is taken as confirmation of a period of increased temperatures .
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Stomata were present, particularly on the upper axes. Their absence on the lower portions of the axes suggests that this part of the plants may have been submerged, and that the plants dwelt in boggy ground or even shallow water. In many fossils these appear to consist of a slit-like opening in the middle of a single elongated guard cell, leading to comparison with the stomata of some mosses. However, this is now thought to result from the loss of the wall separating paired guard cells during fossilisation.
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Plant fossils almost always represent disarticulated parts of plants; even small herbaceous plants are rarely preserved whole. Those few examples of plant fossils that appear to be the remains of whole plants in fact are incomplete as the internal cellular tissue and fine micromorphological detail is normally lost during fossilisation. Plant remains can be preserved in a variety of ways, each revealing different features of the original parent plant. Because of these difficulties, palaeobotanists usually assign different taxonomic names to different parts of the plant in different modes of preservation.
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Furthermore, the lack of a baculum (penis bone) found in all lower primates means that the fossil was from a female. X-rays performed on Ida revealed that her right wrist was healing from a fracture which may have contributed to her death. The scientists speculate whether she was overcome by carbon dioxide fumes while drinking from the Messel lake. Hampered by her broken wrist, she slipped into unconsciousness, was washed into the lake and sank to the bottom, where unique fossilisation conditions preserved her for 47 million years.
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Since the bones are well-preserved and had no gnaw marks, the carcass appears to have been undisturbed by scavengers (suggesting that it was quickly covered by sediment). The disarticulation of the bones may have been the result of soft-tissue decomposition. Parts of the skeleton seem to have weathered to different degrees, perhaps because water levels changed or the sediments shifted (exposing parts of the skeleton). The girdle and limb bones, the dentary, and a rib were broken before fossilisation, perhaps from trampling by large animals while buried.
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The chance of fossilisation is higher when the sedimentation rate is high (so that a carcass is quickly buried), in anoxic environments (where little bacterial activity occurs) or when the organism had a particularly hard skeleton. Larger, well-preserved fossils are relatively rare. Burrows in a turbidite, made by crustaceans, San Vincente Formation (early Eocene) of the Ainsa Basin, southern foreland of the Pyrenees Fossils can be both the direct remains or imprints of organisms and their skeletons. Most commonly preserved are the harder parts of organisms such as bones, shells, and the woody tissue of plants.
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The first 15 million years of the Carboniferous had very limited terrestrial fossils. This gap in the fossil record is called Romer's gap after the American palaentologist Alfred Romer. While it has long been debated whether the gap is a result of fossilisation or relates to an actual event, recent work indicates the gap period saw a drop in atmospheric oxygen levels, indicating some sort of ecological collapse. The gap saw the demise of the Devonian fish-like ichthyostegalian labyrinthodonts, and the rise of the more advanced temnospondyl and reptiliomorphan amphibians that so typify the Carboniferous terrestrial vertebrate fauna.
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Pollen's sporopollenin outer sheath affords it some resistance to the rigours of the fossilisation process that destroy weaker objects; it is also produced in huge quantities. There is an extensive fossil record of pollen grains, often disassociated from their parent plant. The discipline of palynology is devoted to the study of pollen, which can be used both for biostratigraphy and to gain information about the abundance and variety of plants alive — which can itself yield important information about paleoclimates. Also, pollen analysis has been widely used for reconstructing past changes in vegetation and their associated drivers.
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The species Rhinonicteris tedfordi existed in the early Miocene period. The fossil records are the earliest example of an endemic lineage of Australian Rhinonicteris, which includes later material of the genus which is yet to be formally described; the fossil Rhinonicteris material at Riversleigh dates from the Miocene through to the present period. The site was a cave, open to the nearby environment, and contains the remains of probably over ten other microchiropteran species and shells of freshwater snails. The preservation state of a large amount of the type material indicates the fossilisation process began shortly after their deposit.
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The paucity of Ediacaran fossils after the Cambrian could simply be due to conditions that no longer favoured the fossilisation of Ediacaran organisms, which may have continued to thrive unpreserved. However, if they were common, more than the occasional specimen might be expected in exceptionally preserved fossil assemblages (Konservat-Lagerstätten) such as the Burgess Shale and Chengjiang. There are at present no widely accepted reports of Ediacara-type organisms in the Cambrian period, though there are a few disputed reports, as well as unpublished observations of 'vendobiont' fossils from 535 Ma Orsten-type deposits in China.
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Preserved skin, salt- preserved or air-dried, can also be used in certain situations. DNA preservation is difficult because the bone fossilisation degrades and DNA is chemically modified, usually by bacteria and fungi in the soil. The best time to extract DNA from a fossil is when it is freshly out of the ground as it contains six times the DNA when compared to stored bones. The temperature of extraction site also affects the amount of obtainable DNA, evident by a decrease in success rate for DNA amplification if the fossil is found in warmer regions.
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In 1992, anthropologists Geoffrey Raymond Fisk and Gabriele Macho interpreted the left ankle bone Stw 363 as bearing evidence of a healed calcaneal fracture on the heel bone (which was not preserved), which they believed resulted from a fall from a tree. If correct, then the individual was able to survive for a long time despite losing a great deal of function in the left leg. However, they also noted that similar damage could potentially have also been inflicted by calcite deposition and crystallisation during the fossilisation process. Calcaneal fractures have been recorded in humans, and present quite often in arboreal primates.
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In 2015, Akinobu Watanabe and colleagues found that together with Deinocheirus and Archaeornithomimus, Gallimimus had the most pneumatised skeleton among ornithomimosaurs. Pneumatisation is thought to be advantageous for flight in modern birds, but its function in non-avian dinosaurs is not known with certainty. It has been proposed that pneumatisation was used to reduce the mass of large bones, that it was related to high metabolism, balance during locomotion, or used for thermoregulation. Repatriated adult skull, CMMD In 2017, Lee and colleagues suggested various possible taphonomic circumstances (changes during decay and fossilisation) to explain how the Gallimimus foot discovered in 2009 was associated with a trackway.
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Erin derives from Éirinn, the Irish dative case of Éire, which has replaced the nominative case in Déise Irish and some non-standard sub-dialects elsewhere, in Scottish Gaelic (where the usual word for Ireland is ) and Manx (like Irish and Scottish Gaelic, a Goidelic Celtic language), where the word is spelled "Nerin," with the initial n- probably representing a fossilisation of the preposition in/an "in" (cf. Irish in Éirinn, Scottish an Èirinn/ann an Èirinn "in Ireland"). The genitive case, Éireann (e.g. stair na hÉireann "the history of Ireland, Ireland's history"), is found in the Gaelic forms of the titles of companies and institutions in Ireland e.g.
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Psychosynthesis "has always been on the fringes of the 'official' therapy world" and it "is only recently that the concepts and methods of psychoanalysis and group analysis have been introduced into the training and practice of psychosynthesis psychotherapy".Reinhard Kowalski, Discovering Your Self (1993) p. 13. As a result, the movement has been at times exposed to the dangers of fossilisation and cultism, so that on occasion, having "started out reflecting the high- minded spiritual philosophy of its founder, [it] became more and more authoritarian, more and more strident in its conviction that psychosynthesis was the One Truth".Walter T. Anderson, The Upstart Spring (2004) p. 265.
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Left to right: denticles of Paralogania (?), Shielia taiti, Lanarkia horrida The bony scales of the thelodont group, as the most abundant form of fossil, are also the best understood – and thus most useful. The scales were formed and shed throughout the organisms' lifetimes, and quickly separated after their death. Bone – being one of the most resistant materials to the process of fossilisation – often preserves internal detail, which allows the histology and growth of the scales to be studied in detail. The scales consist of a non-growing "crown" composed of dentine, with a sometimes-ornamented enameloid upper surface and an aspidine (acellular bony tissue) base.
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P. oldowayensis skull Pelorovis antiquus, P. turkanensis & P. oldowayensis (from left to right) Pelorovis resembled an African buffalo, although it was larger and possessed longer, curved horns. Pelorovis probably weighed about , with the largest males attaining . This ranks it as one of the largest bovines, and indeed one of the largest ruminants ever to have lived, rivalling the extinct American long-horned bison (Bison latifrons), and the extinct Asiatic giraffid Sivatherium giganteum, as well as the extant African giraffe (Giraffa camelopardis) in weight. The bony cores of the horns were each about long; when covered with keratin (which does not survive fossilisation) they could have been up to twice this length.
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The palate is also somewhat weathered in this specimen. The referred specimen LPB 1993-9 is smaller than the holotype ( long) and also more complete, however it has been subjected to taphonomic distortion during fossilisation that distorts some features. The skull has been laterally compressed, particularly distorting the shape of the zygomatic arches, obscuring details of the palate, twisting the tusks so that they curl inward, and altering the symmetry of the skull in general (although the left orbit appears to have maintained its shape). LBP 1993-9 is also missing the left quadratojugal and stapes, and the quadrates, while the right stapes and epipterygoids are poorly preserved.
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Macroderma godthelpi was discovered in an area of northwest Queensland that was dominated by rainforest during the early Miocene, overlying a karst system that provided roosting opportunities for a diverse array of bat species. The Riversleigh fauna is represented by megadermatid species and others of the order Chiroptera, often creating well preserved fossil depositions at the floor of limestone caves. The sites of former bat eyries at Riversleigh included the remains of themselves and prey selected from the local fauna, with butchered parts and defecated fragments becoming preserved in conditions ideal for fossilisation. A depiction of the species by Peter Schouten was published in 1983, two years before the formal description.
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He then concluded she died from falling out of a tree, and that A. afarensis slept in trees or climbed trees to escape predators. However, similar fracturing is exhibited in many other creatures in the area, including the bones of antelope, elephants, giraffes, and rhinos, and may well simply be taphonomic bias (fracturing was caused by fossilisation). Lucy may also have been killed in an animal attack or a mudslide. The 13 AL 333 individuals are thought to have been deposited at about the same time as one another, bear little evidence of carnivore activity, and were buried on a stretch of a hill.
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Other features originally used to distinguish the species have been recognised as the results of the deformation of the skull after fossilisation. Sereno (2010) remained unconvinced of its validity. ;P. sibiricus Beginning in the 1950s, Russian paleontologists began excavating Psittacosaurus remains at a locality near the village of Shestakovo in the oblast of Kemerovo in Siberia. Two other nearby localities were explored in the 1990s, one of which produced several complete skeletons. This species was named P. sibiricus in 2000 in a scientific paper written by five Russian paleontologists, but credit for the name is officially given to two of those authors, Alexei Voronkevich and Alexander Averianov.
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Feeding traces from skin beetles on the nesting specimen The nesting specimen MPC-D 107/15 has provided much information about the taphonomic processes (changes during decay and fossilisation) in the Baruungoyot Formation. The specimen is preserved in facies that are thought to have been deposited through a sandstorm or dune-shift. It does not seem to have been transported after death, but the body appears to have shifted slightly to the right, indicating the sediment in which it was deposited came towards it from its left side. The neck is curved to the left, the left hand is folded backwards, and the legs are folded into a crouching position.
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The name of the genus is derived from traditional name given by the people of Arnhem Land to the Rainbow serpent. They were large snakes, up to 6 metres long and 300 millimetres thick, that are more closely resemble Varanus (monitors) than small burrowing lizards. John Scanlon has presented this as evidence of descent from the former, rather than burrowing ancestors that evolved into the elongate and legless snakes. The fossil material described by this species includes a rare example of a complete skull and mandible, often crushed in the fossilisation process, that was preserved in the soft limestone of a body of fresh water.
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Most of the tail appears to have been lost before fossilisation, perhaps due to scavenging, or having rotted and floated off. The orientation of the bones indicates that the carcass lay on its back (perhaps tilted slightly to the left, with the right side upwards), which may explain why all the lower teeth had fallen out of their sockets and some upper teeth were still in place. Most of the bones of Portuguese specimen ML1190 were damaged, and some scratches may be marks from small scavengers. The specimen's disarticulation indicates it was transported from a more- terrestrial environment (since many bones are missing), but those found were close together.
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The body of the animal, its viscera, continues to occupy the last chamber of the shell – the living chamber. The septa are perforated by the siphuncle, which runs through each of the internal chambers of the shell. Surrounding the fleshy tube of the siphuncle are structures made of aragonite (a polymorph of calcium carbonate – which during fossilisation is often recrystallized to calcite, a more stable form of calcium carbonate [CaCO3]): septal necks and connecting rings. Some of the earlier nautiloids deposited calcium carbonate in the empty chambers (called cameral deposits) or within the siphuncle (endosiphuncular deposits), a process which may have been connected with controlling buoyancy.
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The sediments of the Yerrapalli Formation are interpreted as fluvial deposits, indicative of a broad, interchannel floodplain environment with seasonal ephemeral stream channels. The climate is thought to have been hot and dry with seasonal rainfall. This is consistent with the preservation state of the fossils, as the remains of Yarasuchus were found dismembered and disarticulated, suggesting the material was left exposed at the surface for a period before being buried by suspended fluvial sediments. There are few plant fossils known from the Yerrapalli Formation, however this is not believed to be due to it being an arid environment, but rather due to the hot and dry conditions being unsuitable to the fossilisation of plant material.
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Bog-wood, also known as abonos and morta, especially amongst pipe smokers, is a material from trees that have been buried in peat bogs and preserved from decay by the acidic and anaerobic bog conditions, sometimes for hundreds or even thousands of years. The wood is usually stained brown by tannins dissolved in the acidic water. Bog-wood represents the early stages in the fossilisation of wood, with further stages ultimately forming jet, lignite and coal over a period of many millions of years. Bog-wood may come from any tree species naturally growing near or in bogs, including oak (Quercus - "bog oak"), pine (Pinus), yew (Taxus), swamp cypress (Taxodium) and kauri (Agathis).
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The first Saccopastore skull, discovered by Sergio Sergi, and the second Saccopastore skull, discovered by Professors Breuil and Blanc, both show greater basicranial flexion compared to those of the Wurmian Neandertals, due to the extreme inclination of the planum sphenoidalis. The skulls' ages likely ranges from 100,000 to 300,000 years, and they show an extremely high level of fossilisation. After being discovered, the skulls were kept at the Institute of Anthropology of the University of Rome until World War II, when they were taken by Professor Sergio Sergi to be preserved and kept safe from German officers who were seeking fossil treasures. After a time, they stayed with Sergi and became part of his own private collection.
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The single skull of Thliptosaurus is nearly complete, but it has been severely crushed and flattened from top-to-bottom (dorsoventrally), and some broken areas of bone at the back of the skull have been restored using plaster. Details and sutures on the top of the skull are readily visible, but poor preservation and over-preparation have obliterated features on the sides and rear of the skull. The lower jaw is firmly occluded to the upper jaw, obscuring some details of the sides of the skull and many of the palate. The generic name is from the Ancient Greek θλῖψις (thlipsis) and σαῦρος (saurus), literally translated to mean "compressed lizard", referring to the flattened nature of the skull from being severely dorsoventrally compressed during fossilisation.
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Chapter IX deals with the fact that the geological record appears to show forms of life suddenly arising, without the innumerable transitional fossils expected from gradual changes. Darwin borrowed Charles Lyell's argument in Principles of Geology that the record is extremely imperfect as fossilisation is a very rare occurrence, spread over vast periods of time; since few areas had been geologically explored, there could only be fragmentary knowledge of geological formations, and fossil collections were very poor. Evolved local varieties which migrated into a wider area would seem to be the sudden appearance of a new species. Darwin did not expect to be able to reconstruct evolutionary history, but continuing discoveries gave him well- founded hope that new finds would occasionally reveal transitional forms.
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The intertemporal region, or bar, is unusually wide for a kingoriid, composed of the broad frontal bones in the front and the flat exposed parietal bones behind them, each contacting with the single preparietal (a unique bone found in dicynodonts and some other therapsids) just behind the eyes. Very unusually for a dicynodont, Thliptosaurus has no visible pineal foramen, and the suture between the parietals appears uninterrupted for their whole length. Even if the parietal foramen existed and was obscured by deformation during fossilisation, it would had to have existed as a very thin slit between the parietals that did not contact the preparietal, which itself would be a highly unusual condition for a dicynodont. However, comparisons with other kingoriids indicate that the absence of the pineal foramen is likely a genuine feature.
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The holotype and only known specimen of Taoheodon, IVPP V 25335, was discovered in the valley of a tributary of the Tao He river, running through the lower part of the Sunjiagou Formation. The Sunjiagou Formation has been dated to the Late Permian (Lopingian epoch), although the exact age of the lower beds has been debated; either representing the late Wuchiapingian age or early Changhsingian. The lower Sunjiagou Formation is composed of grey to greenish-grey mudstones and fine grained sandstones, although the fossil of Taoheodon itself was found contained within an eroded rock nodule. This erosion resulted in the loss of the zygomatic arches and the tip of the snout from the specimen which had been exposed prior to collection, and the specimen has also been slightly compressed from top to bottom during fossilisation.
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Model carcass based on the position of the holotype bones, NHM Charig and Milner presented a possible scenario explaining the taphonomy (changes during decay and fossilisation) of the B. walkeri holotype specimen. The fine-grained sediments around the skeleton, and the fact that the bones were found close together (skull and forelimb elements at one end of the excavation area and the pelvis and hind-limb elements at the other), indicates that the environment was quiet at the time of deposition, and water currents did not carry the carcass far—possibly because the water was shallow. The area where the specimen died seems to have been suitable for a piscivorous animal. It may have caught fish and scavenged on the mud plain, becoming mired before it died and was buried.
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Court dress with exaggerated side-hoops, dating from the 1760s Fashion (and wealth) continued to dictate what was worn on these occasions; but in the late eighteenth century, a degree of fossilisation began to set in, with the result that women in attendance at royal courts were still, in the early nineteenth century, to be seen in garments with side-hoops, redolent of forms of dress fashionable in the mid-1700s. In the 1820s, however, George IV made known his opinion that obsolete side-hooped dresses should no longer be worn; and thereafter fashion began to have more of an impact on the style of dress worn by women at court. Hayashi, wife of Japan's resident minister to the UK, in 1902. Courtly garments, then, can be seen reflecting something of the contemporary fashions of high society, from the expansive skirts and crinolines of the 1850-60s, through the posterior bustles of the 1870s & 80s, right through to the straight gowns of the 1920s.
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Dendrochronology (tree-ring dating) of the timbers has enabled precise dating of the track, showing it was built in 3807 BC. This dating led to claims that the Sweet Track was the oldest roadway in the world, until the discovery in 2009 of a 6,000-year-old trackway built in 4100 BC, in Plumstead, near Belmarsh prison. Analysis of the Sweet Track's timbers has aided research into Neolithic Era dendrochronology; comparisons with wood from the River Trent and a submerged forest at Stolford enabled a fuller mapping of the rings, and their relationship with the climate of the period. The wood used to build the track is now classed as bog-wood, the name given to wood (of any source) that for long periods (sometimes hundreds of thousands of years) has been buried in peat bogs, and kept from decaying by the acidic and anaerobic bog conditions. Bog-wood usually is stained brown by tannins dissolved in the acidic water, and represents an early stage of fossilisation.
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Little is known about the mandible due to its compression during fossilisation, but the angular had a lateral process just below the facet for attachment which, along with the long articular facet enabling a sliding motion, probably allowed Chimaerasuchus to move its lower jaw back and forth in a chewing motion to grind plant matter. The absence of a posterior buttress on the articular facet indicates that the pterygoideus muscle could have generated horizontal force enabling this chewing to take place. The two roughly conical teeth in each premaxilla would have been used for nipping off plant material or possibly for defence, while the molariform, polycuspid teeth in the maxillae (at least four in each) could have ground up the food. Although the dentary teeth are not known, it is very likely that there was one conical pair at the front which fitted in the gap between premaxilla and maxilla, while the remainder worked with the maxillary teeth to grind, indicating that Chimaerasuchus was almost certainly a herbivore.
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Although burrowing reduced the number of environments that could support Burgess Shale-type deposits, it alone cannot explain their demise, and changing ocean chemistry – in particular the oxygenation of ocean sediments – also contributed to the disappearance of Burgess Shale-type preservation. The number of pre-Cambrian assemblages is limited primarily by the rarity of soft-bodied organisms large enough to be preserved; however as more and more Ediacaran sediments are examined, Burgess Shale-type preservation is becoming increasingly well known in this time period. While the post-revolution world was full of scavenging and predatory organisms, the contribution of direct consumption of carcasses to the rarity of post-Cambrian Burgess Shale type lagerstätten was relatively minor, compared to the changes brought about in sediments' chemistry, porosity, and microbiology, which made it difficult for the chemical gradients necessary for soft-tissue mineralisation to develop. Just like microbial mats, environments which could produce this mode of fossilisation became increasingly restricted to harsher and deeper areas, where burrowers could not establish a foothold; as time progressed, the extent of burrowing increased sufficiently to effectively make this mode of preservation impossible.
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