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"Dinosaur bones" redirects here. Fossil_sentence_0

For the band, see Dinosaur Bones. Fossil_sentence_1

For other uses, see Fossil (disambiguation). Fossil_sentence_2

A fossil (from Classical Latin: , literally "obtained by digging") is any preserved remains, impression, or trace of any once-living thing from a past geological age. Fossil_sentence_3

Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood, oil, coal, and DNA remnants. Fossil_sentence_4

The totality of fossils is known as the fossil record. Fossil_sentence_5

Paleontology is the study of fossils: their age, method of formation, and evolutionary significance. Fossil_sentence_6

Specimens are usually considered to be fossils if they are over 10,000 years old. Fossil_sentence_7

The oldest fossils are around 3.48 billion years old to 4.1 billion years old. Fossil_sentence_8

The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils. Fossil_sentence_9

The development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the absolute ages of rocks and the fossils they host. Fossil_sentence_10

There are many processes that lead to fossilization, including permineralization, casts and molds, authigenic mineralization, replacement and recrystallization, adpression, carbonization, and bioimmuration. Fossil_sentence_11

Fossils vary in size from one-micrometre (1 µm) bacteria to dinosaurs and trees, many meters long and weighing many tons. Fossil_sentence_12

A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates, or the chitinous or calcareous exoskeletons of invertebrates. Fossil_sentence_13

Fossils may also consist of the marks left behind by the organism while it was alive, such as animal tracks or feces (coprolites). Fossil_sentence_14

These types of fossil are called trace fossils or ichnofossils, as opposed to body fossils. Fossil_sentence_15

Some fossils are biochemical and are called chemofossils or biosignatures. Fossil_sentence_16

Fossilization processes Fossil_section_0

The process of fossilization varies according to tissue type and external conditions. Fossil_sentence_17

Permineralization Fossil_section_1

Permineralization is a process of fossilization that occurs when an organism is buried. Fossil_sentence_18

The empty spaces within an organism (spaces filled with liquid or gas during life) become filled with mineral-rich groundwater. Fossil_sentence_19

Minerals precipitate from the groundwater, occupying the empty spaces. Fossil_sentence_20

This process can occur in very small spaces, such as within the cell wall of a plant cell. Fossil_sentence_21

Small scale permineralization can produce very detailed fossils. Fossil_sentence_22

For permineralization to occur, the organism must become covered by sediment soon after death, otherwise the remains destroyed by scavengers or decomposition. Fossil_sentence_23

The degree to which the remains are decayed when covered determines the later details of the fossil. Fossil_sentence_24

Some fossils consist only of skeletal remains or teeth; other fossils contain traces of skin, feathers or even soft tissues. Fossil_sentence_25

This is a form of diagenesis. Fossil_sentence_26

Casts and molds Fossil_section_2

In some cases, the original remains of the organism completely dissolve or are otherwise destroyed. Fossil_sentence_27

The remaining organism-shaped hole in the rock is called an external mold. Fossil_sentence_28

If this hole is later filled with other minerals, it is a cast. Fossil_sentence_29

An endocast, or internal mold, is formed when sediments or minerals fill the internal cavity of an organism, such as the inside of a bivalve or snail or the hollow of a skull. Fossil_sentence_30

Authigenic mineralization Fossil_section_3

This is a special form of cast and mold formation. Fossil_sentence_31

If the chemistry is right, the organism (or fragment of organism) can act as a nucleus for the precipitation of minerals such as siderite, resulting in a nodule forming around it. Fossil_sentence_32

If this happens rapidly before significant decay to the organic tissue, very fine three-dimensional morphological detail can be preserved. Fossil_sentence_33

Nodules from the Carboniferous Mazon Creek fossil beds of Illinois, USA, are among the best documented examples of such mineralization. Fossil_sentence_34

Replacement and recrystallization Fossil_section_4

Replacement occurs when the shell, bone or other tissue is replaced with another mineral. Fossil_sentence_35

In some cases mineral replacement of the original shell occurs so gradually and at such fine scales that microstructural features are preserved despite the total loss of original material. Fossil_sentence_36

A shell is said to be recrystallized when the original skeletal compounds are still present but in a different crystal form, as from aragonite to . Fossil_sentence_37

Adpression (compression-impression) Fossil_section_5

Compression fossils, such as those of fossil ferns, are the result of chemical reduction of the complex organic molecules composing the organism's tissues. Fossil_sentence_38

In this case the fossil consists of original material, albeit in a geochemically altered state. Fossil_sentence_39

This chemical change is an expression of diagenesis. Fossil_sentence_40

Often what remains is a carbonaceous film known as a phytoleim, in which case the fossil is known as a compression. Fossil_sentence_41

Often, however, the phytoleim is lost and all that remains is an impression of the organism in the rock—an impression fossil. Fossil_sentence_42

In many cases, however, compressions and impressions occur together. Fossil_sentence_43

For instance, when the rock is broken open, the phytoleim will often be attached to one part (compression), whereas the counterpart will just be an impression. Fossil_sentence_44

For this reason, one term covers the two modes of preservation: adpression. Fossil_sentence_45

Soft tissue, cell and molecular preservation Fossil_section_6

Because of their antiquity, an unexpected exception to the alteration of an organism's tissues by chemical reduction of the complex organic molecules during fossilization has been the discovery of soft tissue in dinosaur fossils, including blood vessels, and the isolation of proteins and evidence for DNA fragments. Fossil_sentence_46

In 2014, Mary Schweitzer and her colleagues reported the presence of iron particles (goethite-aFeO(OH)) associated with soft tissues recovered from dinosaur fossils. Fossil_sentence_47

Based on various experiments that studied the interaction of iron in haemoglobin with blood vessel tissue they proposed that solution hypoxia coupled with iron chelation enhances the stability and preservation of soft tissue and provides the basis for an explanation for the unforeseen preservation of fossil soft tissues. Fossil_sentence_48

However, a slightly older study based on eight taxa ranging in time from the Devonian to the Jurassic found that reasonably well-preserved fibrils that probably represent collagen were preserved in all these fossils and that the quality of preservation depended mostly on the arrangement of the collagen fibers, with tight packing favoring good preservation. Fossil_sentence_49

There seemed to be no correlation between geological age and quality of preservation, within that timeframe. Fossil_sentence_50

Carbonization and coalification Fossil_section_7

Fossils that are carbonized or coalified consist of the organic remains which have been reduced primarily to the chemical element carbon. Fossil_sentence_51

Carbonized fossils consist of a thin film which forms a silhouette of the original organism, and the original organic remains were typically soft tissues. Fossil_sentence_52

Coalified fossils consist primarily of coal, and the original organic remains were typically woody in composition. Fossil_sentence_53


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Bioimmuration Fossil_section_8

Bioimmuration occurs when a skeletal organism overgrows or otherwise subsumes another organism, preserving the latter, or an impression of it, within the skeleton. Fossil_sentence_54

Usually it is a sessile skeletal organism, such as a bryozoan or an oyster, which grows along a substrate, covering other sessile sclerobionts. Fossil_sentence_55

Sometimes the bioimmured organism is soft-bodied and is then preserved in negative relief as a kind of external mold. Fossil_sentence_56

There are also cases where an organism settles on top of a living skeletal organism that grows upwards, preserving the settler in its skeleton. Fossil_sentence_57

Bioimmuration is known in the fossil record from the Ordovician to the Recent. Fossil_sentence_58

Dating Fossil_section_9

Estimating dates Fossil_section_10

Main articles: Geochronology and Relative dating Fossil_sentence_59

Paleontology seeks to map out how life evolved across geologic time. Fossil_sentence_60

A substantial hurdle is the difficulty of working out fossil ages. Fossil_sentence_61

Beds that preserve fossils typically lack the radioactive elements needed for radiometric dating. Fossil_sentence_62

This technique is our only means of giving rocks greater than about 50 million years old an absolute age, and can be accurate to within 0.5% or better. Fossil_sentence_63

Although radiometric dating requires careful laboratory work, its basic principle is simple: the rates at which various radioactive elements decay are known, and so the ratio of the radioactive element to its decay products shows how long ago the radioactive element was incorporated into the rock. Fossil_sentence_64

Radioactive elements are common only in rocks with a volcanic origin, and so the only fossil-bearing rocks that can be dated radiometrically are volcanic ash layers, which may provide termini for the intervening sediments. Fossil_sentence_65

Stratigraphy Fossil_section_11

Consequently, palaeontologists rely on stratigraphy to date fossils. Fossil_sentence_66

Stratigraphy is the science of deciphering the "layer-cake" that is the sedimentary record. Fossil_sentence_67

Rocks normally form relatively horizontal layers, with each layer younger than the one underneath it. Fossil_sentence_68

If a fossil is found between two layers whose ages are known, the fossil's age is claimed to lie between the two known ages. Fossil_sentence_69

Because rock sequences are not continuous, but may be broken up by faults or periods of erosion, it is very difficult to match up rock beds that are not directly adjacent. Fossil_sentence_70

However, fossils of species that survived for a relatively short time can be used to match isolated rocks: this technique is called biostratigraphy. Fossil_sentence_71

For instance, the conodont Eoplacognathus pseudoplanus has a short range in the Middle Ordovician period. Fossil_sentence_72

If rocks of unknown age have traces of E. pseudoplanus, they have a mid-Ordovician age. Fossil_sentence_73

Such index fossils must be distinctive, be globally distributed and occupy a short time range to be useful. Fossil_sentence_74

Misleading results are produced if the index fossils are incorrectly dated. Fossil_sentence_75

Stratigraphy and biostratigraphy can in general provide only relative dating (A was before B), which is often sufficient for studying evolution. Fossil_sentence_76

However, this is difficult for some time periods, because of the problems involved in matching rocks of the same age across continents. Fossil_sentence_77

Family-tree relationships also help to narrow down the date when lineages first appeared. Fossil_sentence_78

For instance, if fossils of B or C date to X million years ago and the calculated "family tree" says A was an ancestor of B and C, then A must have evolved earlier. Fossil_sentence_79

It is also possible to estimate how long ago two living clades diverged, in other words approximately how long ago their last common ancestor must have lived, by assuming that DNA mutations accumulate at a constant rate. Fossil_sentence_80

These "molecular clocks", however, are fallible, and provide only approximate timing: for example, they are not sufficiently precise and reliable for estimating when the groups that feature in the Cambrian explosion first evolved, and estimates produced by different techniques may vary by a factor of two. Fossil_sentence_81

Limitations Fossil_section_12

Further information: Ghost lineage, Signor–Lipps effect, and Biostratigraphy Fossil_sentence_82

Organisms are only rarely preserved as fossils in the best of circumstances, and only a fraction of such fossils have been discovered. Fossil_sentence_83

This is illustrated by the fact that the number of species known through the fossil record is less than 5% of the number of known living species, suggesting that the number of species known through fossils must be far less than 1% of all the species that have ever lived. Fossil_sentence_84

Because of the specialized and rare circumstances required for a biological structure to fossilize, only a small percentage of life-forms can be expected to be represented in discoveries, and each discovery represents only a snapshot of the process of evolution. Fossil_sentence_85

The transition itself can only be illustrated and corroborated by transitional fossils, which will never demonstrate an exact half-way point. Fossil_sentence_86

The fossil record is strongly biased toward organisms with hard-parts, leaving most groups of soft-bodied organisms with little to no role. Fossil_sentence_87

It is replete with the mollusks, the vertebrates, the echinoderms, the brachiopods and some groups of arthropods. Fossil_sentence_88

Sites Fossil_section_13

Lagerstätten Fossil_section_14

Main article: Lagerstätte Fossil_sentence_89

Further information: List of fossil sites Fossil_sentence_90

Fossil sites with exceptional preservation—sometimes including preserved soft tissues—are known as Lagerstätten—German for "storage places". Fossil_sentence_91

These formations may have resulted from carcass burial in an anoxic environment with minimal bacteria, thus slowing decomposition. Fossil_sentence_92

Lagerstätten span geological time from the Cambrian period to the present. Fossil_sentence_93

Worldwide, some of the best examples of near-perfect fossilization are the Cambrian Maotianshan shales and Burgess Shale, the Devonian Hunsrück Slates, the Jurassic Solnhofen limestone, and the Carboniferous Mazon Creek localities. Fossil_sentence_94

Stromatolites Fossil_section_15

Main article: Stromatolites Fossil_sentence_95

Stromatolites are layered accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by biofilms of microorganisms, especially cyanobacteria. Fossil_sentence_96

Stromatolites provide some of the most ancient fossil records of life on Earth, dating back more than 3.5 billion years ago. Fossil_sentence_97

Stromatolites were much more abundant in Precambrian times. Fossil_sentence_98

While older, Archean fossil remains are presumed to be colonies of cyanobacteria, younger (that is, Proterozoic) fossils may be primordial forms of the eukaryote chlorophytes (that is, green algae). Fossil_sentence_99

One genus of stromatolite very common in the geologic record is Collenia. Fossil_sentence_100

The earliest stromatolite of confirmed microbial origin dates to 2.724 billion years ago. Fossil_sentence_101

A 2009 discovery provides strong evidence of microbial stromatolites extending as far back as 3.45 billion years ago. Fossil_sentence_102

Stromatolites are a major constituent of the fossil record for life's first 3.5 billion years, peaking about 1.25 billion years ago. Fossil_sentence_103

They subsequently declined in abundance and diversity, which by the start of the Cambrian had fallen to 20% of their peak. Fossil_sentence_104

The most widely supported explanation is that stromatolite builders fell victims to grazing creatures (the Cambrian substrate revolution), implying that sufficiently complex organisms were common over 1 billion years ago. Fossil_sentence_105

The connection between grazer and stromatolite abundance is well documented in the younger Ordovician evolutionary radiation; stromatolite abundance also increased after the end-Ordovician and end-Permian extinctions decimated marine animals, falling back to earlier levels as marine animals recovered. Fossil_sentence_106

Fluctuations in metazoan population and diversity may not have been the only factor in the reduction in stromatolite abundance. Fossil_sentence_107

Factors such as the chemistry of the environment may have been responsible for changes. Fossil_sentence_108

While prokaryotic cyanobacteria themselves reproduce asexually through cell division, they were instrumental in priming the environment for the evolutionary development of more complex eukaryotic organisms. Fossil_sentence_109

Cyanobacteria (as well as extremophile Gammaproteobacteria) are thought to be largely responsible for increasing the amount of oxygen in the primeval earth's atmosphere through their continuing photosynthesis. Fossil_sentence_110

Cyanobacteria use water, carbon dioxide and sunlight to create their food. Fossil_sentence_111

A layer of mucus often forms over mats of cyanobacterial cells. Fossil_sentence_112

In modern microbial mats, debris from the surrounding habitat can become trapped within the mucus, which can be cemented by the calcium carbonate to grow thin laminations of limestone. Fossil_sentence_113

These laminations can accrete over time, resulting in the banded pattern common to stromatolites. Fossil_sentence_114

The domal morphology of biological stromatolites is the result of the vertical growth necessary for the continued infiltration of sunlight to the organisms for photosynthesis. Fossil_sentence_115

Layered spherical growth structures termed oncolites are similar to stromatolites and are also known from the fossil record. Fossil_sentence_116

Thrombolites are poorly laminated or non-laminated clotted structures formed by cyanobacteria common in the fossil record and in modern sediments. Fossil_sentence_117

The Zebra River Canyon area of the Kubis platform in the deeply dissected Zaris Mountains of southwestern Namibia provides an extremely well exposed example of the thrombolite-stromatolite-metazoan reefs that developed during the Proterozoic period, the stromatolites here being better developed in updip locations under conditions of higher current velocities and greater sediment influx. Fossil_sentence_118

Types Fossil_section_16

Index Fossil_section_17

Main article: Index fossil Fossil_sentence_119

Index fossils (also known as guide fossils, indicator fossils or zone fossils) are fossils used to define and identify geologic periods (or faunal stages). Fossil_sentence_120

They work on the premise that, although different sediments may look different depending on the conditions under which they were deposited, they may include the remains of the same species of fossil. Fossil_sentence_121

The shorter the species' time range, the more precisely different sediments can be correlated, and so rapidly evolving species' fossils are particularly valuable. Fossil_sentence_122

The best index fossils are common, easy to identify at species level and have a broad distribution—otherwise the likelihood of finding and recognizing one in the two sediments is poor. Fossil_sentence_123

Trace Fossil_section_18

Main article: Trace fossil Fossil_sentence_124

Trace fossils consist mainly of tracks and burrows, but also include coprolites (fossil feces) and marks left by feeding. Fossil_sentence_125

Trace fossils are particularly significant because they represent a data source that is not limited to animals with easily fossilized hard parts, and they reflect animal behaviours. Fossil_sentence_126

Many traces date from significantly earlier than the body fossils of animals that are thought to have been capable of making them. Fossil_sentence_127

Whilst exact assignment of trace fossils to their makers is generally impossible, traces may for example provide the earliest physical evidence of the appearance of moderately complex animals (comparable to earthworms). Fossil_sentence_128

Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. Fossil_sentence_129

They were first described by William Buckland in 1829. Fossil_sentence_130

Prior to this they were known as "fossil fir cones" and "bezoar stones." Fossil_sentence_131

They serve a valuable purpose in paleontology because they provide direct evidence of the predation and diet of extinct organisms. Fossil_sentence_132

Coprolites may range in size from a few millimetres to over 60 centimetres. Fossil_sentence_133


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Transitional Fossil_section_19

Main article: Transitional fossil Fossil_sentence_134

Further information: List of transitional fossils Fossil_sentence_135

A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group. Fossil_sentence_136

This is especially important where the descendant group is sharply differentiated by gross anatomy and mode of living from the ancestral group. Fossil_sentence_137

Because of the incompleteness of the fossil record, there is usually no way to know exactly how close a transitional fossil is to the point of divergence. Fossil_sentence_138

These fossils serve as a reminder that taxonomic divisions are human constructs that have been imposed in hindsight on a continuum of variation. Fossil_sentence_139

Microfossils Fossil_section_20

Main article: Micropaleontology Fossil_sentence_140

Microfossil is a descriptive term applied to fossilized plants and animals whose size is just at or below the level at which the fossil can be analyzed by the naked eye. Fossil_sentence_141

A commonly applied cutoff point between "micro" and "macro" fossils is 1 mm. Fossil_sentence_142

Microfossils may either be complete (or near-complete) organisms in themselves (such as the marine plankters foraminifera and coccolithophores) or component parts (such as small teeth or spores) of larger animals or plants. Fossil_sentence_143

Microfossils are of critical importance as a reservoir of paleoclimate information, and are also commonly used by biostratigraphers to assist in the correlation of rock units. Fossil_sentence_144

Resin Fossil_section_21

Main article: Amber Fossil_sentence_145

Fossil resin (colloquially called amber) is a natural polymer found in many types of strata throughout the world, even the Arctic. Fossil_sentence_146

The oldest fossil resin dates to the Triassic, though most dates to the Cenozoic. Fossil_sentence_147

The excretion of the resin by certain plants is thought to be an evolutionary adaptation for protection from insects and to seal wounds. Fossil_sentence_148

Fossil resin often contains other fossils called inclusions that were captured by the sticky resin. Fossil_sentence_149

These include bacteria, fungi, other plants, and animals. Fossil_sentence_150

Animal inclusions are usually small invertebrates, predominantly arthropods such as insects and spiders, and only extremely rarely a vertebrate such as a small lizard. Fossil_sentence_151

Preservation of inclusions can be exquisite, including small fragments of DNA. Fossil_sentence_152

Derived, or reworked Fossil_section_22

See also: Zombie taxon Fossil_sentence_153

A derived, reworked or remanié fossil is a fossil found in rock that accumulated significantly later than when the fossilized animal or plant died. Fossil_sentence_154

Reworked fossils are created by erosion exhuming (freeing) fossils from the rock formation in which they were originally deposited and their redeposition in a younger sedimentary deposit. Fossil_sentence_155

Wood Fossil_section_23

Main article: Fossil wood Fossil_sentence_156

Fossil wood is wood that is preserved in the fossil record. Fossil_sentence_157

Wood is usually the part of a plant that is best preserved (and most easily found). Fossil_sentence_158

Fossil wood may or may not be petrified. Fossil_sentence_159

The fossil wood may be the only part of the plant that has been preserved: therefore such wood may get a special kind of botanical name. Fossil_sentence_160

This will usually include "xylon" and a term indicating its presumed affinity, such as Araucarioxylon (wood of Araucaria or some related genus), Palmoxylon (wood of an indeterminate palm), or Castanoxylon (wood of an indeterminate chinkapin). Fossil_sentence_161

Subfossil Fossil_section_24

Main article: Subfossil Fossil_sentence_162

The term subfossil can be used to refer to remains, such as bones, nests, or defecations, whose fossilization process is not complete, either because the length of time since the animal involved was living is too short (less than 10,000 years) or because the conditions in which the remains were buried were not optimal for fossilization. Fossil_sentence_163

Subfossils are often found in caves or other shelters where they can be preserved for thousands of years. Fossil_sentence_164

The main importance of subfossil vs. fossil remains is that the former contain organic material, which can be used for radiocarbon dating or extraction and sequencing of DNA, protein, or other biomolecules. Fossil_sentence_165

Additionally, isotope ratios can provide much information about the ecological conditions under which extinct animals lived. Fossil_sentence_166

Subfossils are useful for studying the evolutionary history of an environment and can be important to studies in paleoclimatology. Fossil_sentence_167

Subfossils are often found in depositionary environments, such as lake sediments, oceanic sediments, and soils. Fossil_sentence_168

Once deposited, physical and chemical weathering can alter the state of preservation. Fossil_sentence_169

Chemical fossils Fossil_section_25

See also: Biosignature Fossil_sentence_170

Chemical fossils, or chemofossils, are chemicals found in rocks and fossil fuels (petroleum, coal, and natural gas) that provide an organic signature for ancient life. Fossil_sentence_171

Molecular fossils and isotope ratios represent two types of chemical fossils. Fossil_sentence_172

The oldest traces of life on Earth are fossils of this type, including carbon isotope anomalies found in zircons that imply the existence of life as early as 4.1 billion years ago. Fossil_sentence_173

Astrobiology Fossil_section_26

It has been suggested that biominerals could be important indicators of extraterrestrial life and thus could play an important role in the search for past or present life on the planet Mars. Fossil_sentence_174

Furthermore, organic components (biosignatures) that are often associated with biominerals are believed to play crucial roles in both pre-biotic and biotic reactions. Fossil_sentence_175

On 24 January 2014, NASA reported that current studies by the Curiosity and Opportunity rovers on Mars will now be searching for evidence of ancient life, including a biosphere based on autotrophic, chemotrophic and/or chemolithoautotrophic microorganisms, as well as ancient water, including fluvio-lacustrine environments (plains related to ancient rivers or lakes) that may have been habitable. Fossil_sentence_176

The search for evidence of habitability, taphonomy (related to fossils), and organic carbon on the planet Mars is now a primary NASA objective. Fossil_sentence_177

Pseudofossils Fossil_section_27

Main article: Pseudofossils Fossil_sentence_178

Pseudofossils are visual patterns in rocks that are produced by geologic processes rather than biologic processes. Fossil_sentence_179

They can easily be mistaken for real fossils. Fossil_sentence_180

Some pseudofossils, such as geological dendrite crystals, are formed by naturally occurring fissures in the rock that get filled up by percolating minerals. Fossil_sentence_181

Other types of pseudofossils are kidney ore (round shapes in iron ore) and moss agates, which look like moss or plant leaves. Fossil_sentence_182

Concretions, spherical or ovoid-shaped nodules found in some sedimentary strata, were once thought to be dinosaur eggs, and are often mistaken for fossils as well. Fossil_sentence_183

History of the study of fossils Fossil_section_28

Main article: History of paleontology Fossil_sentence_184

See also: Timeline of paleontology Fossil_sentence_185

Gathering fossils dates at least to the beginning of recorded history. Fossil_sentence_186

The fossils themselves are referred to as the fossil record. Fossil_sentence_187

The fossil record was one of the early sources of data underlying the study of evolution and continues to be relevant to the history of life on Earth. Fossil_sentence_188

Paleontologists examine the fossil record to understand the process of evolution and the way particular species have evolved. Fossil_sentence_189

Ancient civilizations Fossil_section_29

Fossils have been visible and common throughout most of natural history, and so documented human interaction with them goes back as far as recorded history, or earlier. Fossil_sentence_190

There are many examples of paleolithic stone knives in Europe, with fossil echinoderms set precisely at the hand grip, going all the way back to Homo heidelbergensis and neanderthals. Fossil_sentence_191

These ancient peoples also drilled holes through the center of those round fossil shells, apparently using them as beads for necklaces. Fossil_sentence_192

The ancient Egyptians gathered fossils of species that resembled the bones of modern species they worshipped. Fossil_sentence_193

The god Set was associated with the hippopotamus, therefore fossilized bones of hippo-like species were kept in that deity's temples. Fossil_sentence_194

Five-rayed fossil sea urchin shells were associated with the deity Sopdu, the Morning Star, equivalent of Venus in Roman mythology. Fossil_sentence_195

Fossils appear to have directly contributed to the mythology of many civilizations, including the ancient Greeks. Fossil_sentence_196

Classical Greek historian Herodotos wrote of an area near Hyperborea where gryphons protected golden treasure. Fossil_sentence_197

There was indeed gold mining in that approximate region, where beaked Protoceratops skulls were common as fossils. Fossil_sentence_198

A later Greek scholar, Aristotle, eventually realized that fossil seashells from rocks were similar to those found on the beach, indicating the fossils were once living animals. Fossil_sentence_199

He had previously explained them in terms of vaporous exhalations, which Persian polymath Avicenna modified into the theory of petrifying fluids (succus lapidificatus). Fossil_sentence_200

Recognition of fossil seashells as originating in the sea was built upon in the 14th century by Albert of Saxony, and accepted in some form by most naturalists by the 16th century. Fossil_sentence_201

Roman naturalist Pliny the Elder wrote of "tongue stones", which he called glossopetra. Fossil_sentence_202

These were fossil shark teeth, thought by some classical cultures to look like the tongues of people or snakes. Fossil_sentence_203

He also wrote about the horns of Ammon, which are fossil ammonites, from whence the group of shelled octopus-cousins ultimately draws its modern name. Fossil_sentence_204

Pliny also makes one of the earlier known references to toadstones, thought until the 18th century to be a magical cure for poison originating in the heads of toads, but which are fossil teeth from Lepidotes, a Cretaceous ray-finned fish. Fossil_sentence_205

The Plains tribes of North America are thought to have similarly associated fossils, such as the many intact pterosaur fossils naturally exposed in the region, with their own mythology of the thunderbird. Fossil_sentence_206

There is no such direct mythological connection known from prehistoric Africa, but there is considerable evidence of tribes there excavating and moving fossils to ceremonial sites, apparently treating them with some reverence. Fossil_sentence_207

In Japan, fossil shark teeth were associated with the mythical tengu, thought to be the razor-sharp claws of the creature, documented some time after the 8th century AD. Fossil_sentence_208

In medieval China, the fossil bones of ancient mammals including Homo erectus were often mistaken for "dragon bones" and used as medicine and aphrodisiacs. Fossil_sentence_209

In addition, some of these fossil bones are collected as "art" by scholars, who left scripts on various artifacts, indicating the time they were added to a collection. Fossil_sentence_210

One good example is the famous scholar Huang Tingjian of the South Song Dynasty during the 11th century, who kept a specific seashell fossil with his own poem engraved on it. Fossil_sentence_211

In the West fossilized sea creatures on mountainsides were seen as proof of the biblical deluge. Fossil_sentence_212

In 1027, the Persian Avicenna explained fossils' stoniness in The Book of Healing: Fossil_sentence_213

From the 13th century to the present day, scholars pointed out that the fossil skulls of Deinotherium giganteum, found in Crete and Greece, might have been interpreted as being the skulls of the Cyclopes of Greek mythology, and are possibly the origin of that Greek myth. Fossil_sentence_214

Their skulls appear to have a single eye-hole in the front, just like their modern elephant cousins, though in fact it's actually the opening for their trunk. Fossil_sentence_215

In Norse mythology, echinoderm shells (the round five-part button left over from a sea urchin) were associated with the god Thor, not only being incorporated in thunderstones, representations of Thor's hammer and subsequent hammer-shaped crosses as Christianity was adopted, but also kept in houses to garner Thor's protection. Fossil_sentence_216

These grew into the shepherd's crowns of English folklore, used for decoration and as good luck charms, placed by the doorway of homes and churches. Fossil_sentence_217

In Suffolk, a different species was used as a good-luck charm by bakers, who referred to them as fairy loaves, associating them with the similarly shaped loaves of bread they baked. Fossil_sentence_218

Early modern explanations Fossil_section_30

More scientific views of fossils emerged during the Renaissance. Fossil_sentence_219

Leonardo da Vinci concurred with Aristotle's view that fossils were the remains of ancient life. Fossil_sentence_220

For example, da Vinci noticed discrepancies with the biblical flood narrative as an explanation for fossil origins: Fossil_sentence_221

In 1666, Nicholas Steno examined a shark, and made the association of its teeth with the "tongue stones" of ancient Greco-Roman mythology, concluding that those were not in fact the tongues of venomous snakes, but the teeth of some long-extinct species of shark. Fossil_sentence_222

Robert Hooke (1635-1703) included micrographs of fossils in his Micrographia and was among the first to observe fossil forams. Fossil_sentence_223

His observations on fossils, which he stated to be the petrified remains of creatures some of which no longer existed, were published posthumously in 1705. Fossil_sentence_224

William Smith (1769–1839), an English canal engineer, observed that rocks of different ages (based on the law of superposition) preserved different assemblages of fossils, and that these assemblages succeeded one another in a regular and determinable order. Fossil_sentence_225

He observed that rocks from distant locations could be correlated based on the fossils they contained. Fossil_sentence_226

He termed this the principle of faunal succession. Fossil_sentence_227

This principle became one of Darwin's chief pieces of evidence that biological evolution was real. Fossil_sentence_228

Georges Cuvier came to believe that most if not all the animal fossils he examined were remains of extinct species. Fossil_sentence_229

This led Cuvier to become an active proponent of the geological school of thought called catastrophism. Fossil_sentence_230

Near the end of his 1796 paper on living and fossil elephants he said: Fossil_sentence_231

Interest in fossils, and geology more generally, expanded during the early nineteenth century. Fossil_sentence_232

In Britain, Mary Anning's discoveries of fossils, including the first complete ichthyosaur and a complete plesiosaurus skeleton, sparked both public and scholarly interest. Fossil_sentence_233

Linnaeus and Darwin Fossil_section_31

Early naturalists well understood the similarities and differences of living species leading Linnaeus to develop a hierarchical classification system still in use today. Fossil_sentence_234

Darwin and his contemporaries first linked the hierarchical structure of the tree of life with the then very sparse fossil record. Fossil_sentence_235

Darwin eloquently described a process of descent with modification, or evolution, whereby organisms either adapt to natural and changing environmental pressures, or they perish. Fossil_sentence_236

When Darwin wrote On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, the oldest animal fossils were those from the Cambrian Period, now known to be about 540 million years old. Fossil_sentence_237

He worried about the absence of older fossils because of the implications on the validity of his theories, but he expressed hope that such fossils would be found, noting that: "only a small portion of the world is known with accuracy." Fossil_sentence_238

Darwin also pondered the sudden appearance of many groups (i.e. phyla) in the oldest known Cambrian fossiliferous strata. Fossil_sentence_239

After Darwin Fossil_section_32

Since Darwin's time, the fossil record has been extended to between 2.3 and 3.5 billion years. Fossil_sentence_240

Most of these Precambrian fossils are microscopic bacteria or microfossils. Fossil_sentence_241

However, macroscopic fossils are now known from the late Proterozoic. Fossil_sentence_242

The Ediacara biota (also called Vendian biota) dating from 575 million years ago collectively constitutes a richly diverse assembly of early multicellular eukaryotes. Fossil_sentence_243

The fossil record and faunal succession form the basis of the science of biostratigraphy or determining the age of rocks based on embedded fossils. Fossil_sentence_244

For the first 150 years of geology, biostratigraphy and superposition were the only means for determining the relative age of rocks. Fossil_sentence_245

The geologic time scale was developed based on the relative ages of rock strata as determined by the early paleontologists and stratigraphers. Fossil_sentence_246

Since the early years of the twentieth century, absolute dating methods, such as radiometric dating (including potassium/argon, argon/argon, uranium series, and, for very recent fossils, radiocarbon dating) have been used to verify the relative ages obtained by fossils and to provide absolute ages for many fossils. Fossil_sentence_247

Radiometric dating has shown that the earliest known stromatolites are over 3.4 billion years old. Fossil_sentence_248

Modern era Fossil_section_33

Paleontology has joined with evolutionary biology to share the interdisciplinary task of outlining the tree of life, which inevitably leads backwards in time to Precambrian microscopic life when cell structure and functions evolved. Fossil_sentence_249

Earth's deep time in the Proterozoic and deeper still in the Archean is only "recounted by microscopic fossils and subtle chemical signals." Fossil_sentence_250

Molecular biologists, using phylogenetics, can compare protein amino acid or nucleotide sequence homology (i.e., similarity) to evaluate taxonomy and evolutionary distances among organisms, with limited statistical confidence. Fossil_sentence_251

The study of fossils, on the other hand, can more specifically pinpoint when and in what organism a mutation first appeared. Fossil_sentence_252

Phylogenetics and paleontology work together in the clarification of science's still dim view of the appearance of life and its evolution. Fossil_sentence_253

Niles Eldredge's study of the Phacops trilobite genus supported the hypothesis that modifications to the arrangement of the trilobite's eye lenses proceeded by fits and starts over millions of years during the Devonian. Fossil_sentence_254

Eldredge's interpretation of the Phacops fossil record was that the aftermaths of the lens changes, but not the rapidly occurring evolutionary process, were fossilized. Fossil_sentence_255

This and other data led Stephen Jay Gould and Niles Eldredge to publish their seminal paper on punctuated equilibrium in 1971. Fossil_sentence_256

Synchrotron X-ray tomographic analysis of early Cambrian bilaterian embryonic microfossils yielded new insights of metazoan evolution at its earliest stages. Fossil_sentence_257

The tomography technique provides previously unattainable three-dimensional resolution at the limits of fossilization. Fossil_sentence_258

Fossils of two enigmatic bilaterians, the worm-like Markuelia and a putative, primitive protostome, Pseudooides, provide a peek at germ layer embryonic development. Fossil_sentence_259

These 543-million-year-old embryos support the emergence of some aspects of arthropod development earlier than previously thought in the late Proterozoic. Fossil_sentence_260

The preserved embryos from China and Siberia underwent rapid diagenetic phosphatization resulting in exquisite preservation, including cell structures. Fossil_sentence_261

This research is a notable example of how knowledge encoded by the fossil record continues to contribute otherwise unattainable information on the emergence and development of life on Earth. Fossil_sentence_262

For example, the research suggests Markuelia has closest affinity to priapulid worms, and is adjacent to the evolutionary branching of Priapulida, Nematoda and Arthropoda. Fossil_sentence_263

Trading and collecting Fossil_section_34

Main articles: Fossil trading and Fossil collecting Fossil_sentence_264

Fossil trading is the practice of buying and selling fossils. Fossil_sentence_265

This is many times done illegally with artifacts stolen from research sites, costing many important scientific specimens each year. Fossil_sentence_266

The problem is quite pronounced in China, where many specimens have been stolen. Fossil_sentence_267

Fossil collecting (sometimes, in a non-scientific sense, fossil hunting) is the collection of fossils for scientific study, hobby, or profit. Fossil_sentence_268

Fossil collecting, as practiced by amateurs, is the predecessor of modern paleontology and many still collect fossils and study fossils as amateurs. Fossil_sentence_269

Professionals and amateurs alike collect fossils for their scientific value. Fossil_sentence_270

Fossils as medicine Fossil_section_35

These is some medicinal and preventive use for some fossils. Fossil_sentence_271

Largely the use of fossils as medicine is a matter of placebo effect. Fossil_sentence_272

However, the consumption of certain fossils has been proven to help against stomach acidity and mineral depletion. Fossil_sentence_273

The use of fossils to address health issues is rooted in traditional medicine and include the use of fossils as talismans. Fossil_sentence_274

The specific fossil to use to alleviate or cure an illness is often based on its resemblance of the fossils and the symptoms or affected organ. Fossil_sentence_275

The use dinosaur bones as "dragon bones" has persisted in Traditional Chinese medicine into modern times, with Mid Cretaceous dinosaur bones being used for the purpose in Ruyang County during the early 21st century. Fossil_sentence_276

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