A FOSSIL (from Classical
Latin fossilis; literally, "obtained by
digging") is any preserved remains, impression, or trace of any
once-living thing from a past geological age . Examples include bones,
shells, exoskeletons , stone imprints of animals or microbes , hair,
petrified wood , oil, coal, and
DNA remnants. The totality of fossils
is known as the fossil record.
Paleontology is the study of fossils: their age, method of formation,
and evolutionary significance. Specimens are usually considered to be
fossils if they are over 10,000 years old. The oldest fossils are
from around 3.48 billion years old to 4.1 billion years old. 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. 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.
There are many processes that lead to fossilization, including
permineralization , casts and molds, authigenic mineralization,
replacement and recrystalization, adpression, carbonization , and
Fossil of an
Fossils vary in size from one micrometer bacteria to dinosaurs and
trees, many meters long and weighing many tons. 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 .
Fossils may also consist of the marks left behind
by the organism while it was alive, such as animal tracks or feces
(coprolites ). These types of fossil are called trace fossils or
ichnofossils, as opposed to body fossils. Some fossils are biochemical
and are called chemofossils or biosignatures .
* 1.2 Casts and molds
* 1.3 Authigenic mineralization
* 1.4 Replacement and recrystallization
* 1.5 Adpression (compression-impression)
* 1.5.1 Soft tissue, cell and molecular preservation
* 1.7 Bioimmuration
* 2 Dating
* 2.1 Estimating dates
* 2.2 Limitations
* 3 Sites
* 3.1 Lagerstätten
* 4 Types
* 4.1 Index
* 4.2 Trace
* 4.3 Transitional
* 4.4 Microfossils
* 4.5 Resin
* 4.6 Derived
* 4.7 Wood
* 4.9 Chemical fossils
* 5 Astrobiology
* 7 History of the study of fossils
* 7.1 Before Darwin
* 7.2 Linnaeus and Darwin
* 7.3 After Darwin
* 7.4 Modern era
* 8 Trading and collecting
* 9 Gallery
* 10 See also
* 11 References
* 12 Further reading
* 13 External links
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The process of fossilization varies according to tissue type and
Silicified (replaced with silica) fossils from the Road Canyon
Permian of Texas).
Permineralization is a process of fossilization that occurs when an
organism is buried. The empty spaces within an organism (spaces filled
with liquid or gas during life) become filled with mineral-rich
groundwater. Minerals precipitate from the groundwater, occupying the
empty spaces. This process can occur in very small spaces, such as
within the cell wall of a plant cell . Small scale permineralization
can produce very detailed fossils. For permineralization to occur, the
organism must become covered by sediment soon after death or soon
after the initial decay process. The degree to which the remains are
decayed when covered determines the later details of the fossil. Some
fossils consist only of skeletal remains or teeth; other fossils
contain traces of skin , feathers or even soft tissues. This is a form
of diagenesis .
CASTS AND MOLDS
External mold of a bivalve from the
Logan Formation , Lower
Carboniferous , Ohio
In some cases the original remains of the organism completely
dissolve or are otherwise destroyed. The remaining organism-shaped
hole in the rock is called an external mold. If this hole is later
filled with other minerals, it is a cast. 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
This is a special form of cast and mold formation. 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. If this happens rapidly before significant
decay to the organic tissue, very fine three-dimensional morphological
detail can be preserved. Nodules from the
Carboniferous Mazon Creek
fossil beds of Illinois, USA, are among the best documented examples
of such mineralization.
REPLACEMENT AND RECRYSTALLIZATION
Recrystallized scleractinian coral (aragonite to calcite) from
Jurassic of southern Israel
Replacement occurs when the shell, bone or other tissue is replaced
with another mineral. 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. 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 calcite .
Compression fossils , such as those of fossil ferns, are the result
of chemical reduction of the complex organic molecules composing the
organism's tissues. In this case the fossil consists of original
material, albeit in a geochemically altered state. This chemical
change is an expression of diagenesis . Often what remains is a
carbonaceous film known as a phytoleim, in which case the fossil is
known as a compression. Often, however, the phytoleim is lost and all
that remains is an impression of the organism in the rock—an
impression fossil. In many cases, however, compressions and
impressions occur together. 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. For this reason,
one term covers the two modes of preservation: adpression.
Soft Tissue, Cell And Molecular Preservation
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. In 2014, Mary Schweitzer
and her colleagues reported the presence of iron particles (goethite
-aFeO(OH)) associated with soft tissues recovered from dinosaur
fossils. 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.
However, a slightly older study based on eight taxa ranging in time
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. There seemed to be no correlation between geological
age and quality of preservation, within that timeframe.
Carbonaceous films are thin coatings which consist predominantly of
the chemical element carbon . The soft tissues of organisms are made
largely of organic carbon compounds and during diagenesis under
reducing conditions only a thin film of carbon residue is left which
forms a silhouette of the original organism.
The star-shaped holes (Catellocaula vallata) in this Upper
Ordovician bryozoan represent a soft-bodied organism preserved by
bioimmuration in the bryozoan skeleton.
Bioimmuration occurs when a skeletal organism overgrows or otherwise
subsumes another organism, preserving the latter, or an impression of
it, within the skeleton. Usually it is a sessile skeletal organism,
such as a bryozoan or an oyster , which grows along a substrate ,
covering other sessile sclerobionts . Sometimes the bioimmured
organism is soft-bodied and is then preserved in negative relief as a
kind of external mold. There are also cases where an organism settles
on top of a living skeletal organism that grows upwards, preserving
the settler in its skeleton. Bioimmuration is known in the fossil
record from the
Ordovician to the Recent.
Life timeline view • discuss • edit -4500 — – -4000 —
– -3500 — – -3000 — – -2500 — – -2000 — – -1500 —
– -1000 — – -500 — – 0 — WATER Single-celled
life PHOTOSYNTHESIS EUKARYOTES Multicellular
life LAND LIFE DINOSAURS MAMMALS FLOWERS ←
Earliest Earth (−4540 ) ← Earliest water ← Earliest
life ← LHB meteorites ← Earliest oxygen ←
Atmospheric oxygen ←
Oxygen crisis ← Earliest sexual
Ediacara biota ←
← Earliest humans P
n Pongola Huronian
Cryogenian Andean Karoo Quaternary
Axis scale : millions of years ago
Orange labels: ICE AGES.
Human timeline and Nature timeline
Paleontology seeks to map out how life evolved across geologic time.
A substantial hurdle is the difficulty of working out fossil ages.
Beds that preserve fossils typically lack the radioactive elements
needed for radiometric dating . 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. 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. 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.
Consequently, palaeontologists rely on stratigraphy to date fossils.
Stratigraphy is the science of deciphering the "layer-cake" that is
the sedimentary record. Rocks normally form relatively horizontal
layers, with each layer younger than the one underneath it. 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. 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. However, fossils of species that survived
for a relatively short time can be used to match isolated rocks: this
technique is called biostratigraphy. For instance, the conodont
Eoplacognathus pseudoplanus has a short range in the Middle Ordovician
period. If rocks of unknown age have traces of E. pseudoplanus, they
have a mid-
Ordovician age. Such index fossils must be distinctive, be
globally distributed and occupy a short time range to be useful.
Misleading results are produced if the index fossils are incorrectly
Stratigraphy and biostratigraphy can in general provide only
relative dating (A was before B), which is often sufficient for
studying evolution. However, this is difficult for some time periods,
because of the problems involved in matching rocks of the same age
across continents . Family-tree relationships also help to narrow
down the date when lineages first appeared. 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.
It is also possible to estimate how long ago two living clades
diverged – i.e. approximately how long ago their last common
ancestor must have lived – by assuming that
DNA mutations accumulate
at a constant rate. 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.
Ghost lineage ,
Signor–Lipps effect , and
Biostratigraphy Some of the most remarkable gaps in the fossil
record (as of October 2013) show slanting toward organisms with hard
Organisms are only rarely preserved as fossils in the best of
circumstances, and only a fraction of such fossils have been
discovered. 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. 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. The
transition itself can only be illustrated and corroborated by
transitional fossils, which will never demonstrate an exact half-way
The fossil record is strongly biased toward organisms with
hard-parts, leaving most groups of soft-bodied organisms with little
to no role. It is replete with the mollusks , the vertebrates , the
echinoderms , the brachiopods and some groups of arthropods .
Lagerstätte Further information: List of fossil sites
Fossil sites with exceptional preservation—sometimes including
preserved soft tissues—are known as Lagerstätten - German for
"storage places". These formations may have resulted from carcass
burial in an anoxic environment with minimal bacteria, thus slowing
decomposition. Lagerstätten span geological time from the Cambrian
period to the present . Worldwide, some of the best examples of
near-perfect fossilization are the
Maotianshan shales and
Burgess Shale , the
Hunsrück Slates , the
limestone , and the
Mazon Creek localities.
Bolivia , South America
Stromatolites are layered accretionary structures formed in shallow
water by the trapping, binding and cementation of sedimentary grains
by biofilms of microorganisms , especially cyanobacteria .
Stromatolites provide some of the most ancient fossil records of life
on Earth, dating back more than 3.5 billion years ago.
Stromatolites were much more abundant in Precambrian times. While
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
). One genus of stromatolite very common in the geologic record is
Collenia . The earliest stromatolite of confirmed microbial origin
dates to 2.724 billion years ago.
A 2009 discovery provides strong evidence of microbial stromatolites
extending as far back as 3.45 billion years ago.
Stromatolites are a major constituent of the fossil record for life's
first 3.5 billion years, peaking about 1.25 billion years ago. They
subsequently declined in abundance and diversity, which by the start
Cambrian had fallen to 20% of their peak. 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.
The connection between grazer and stromatolite abundance is well
documented in the younger
Ordovician evolutionary radiation ;
stromatolite abundance also increased after the end-
Permian extinctions decimated marine animals, falling back to
earlier levels as marine animals recovered. Fluctuations in metazoan
population and diversity may not have been the only factor in the
reduction in stromatolite abundance. Factors such as the chemistry of
the environment may have been responsible for changes.
While prokaryotic cyanobacteria themselves reproduce asexually
through cell division, they were instrumental in priming the
environment for the evolutionary development of more complex
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 .
Cyanobacteria use water ,
carbon dioxide and sunlight to create their food. A layer of mucus
often forms over mats of cyanobacterial cells. 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 . These laminations can accrete over time,
resulting in the banded pattern common to stromatolites. 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. Layered spherical growth structures
termed oncolites are similar to stromatolites and are also known from
the fossil record . Thrombolites are poorly laminated or non-laminated
clotted structures formed by cyanobacteria common in the fossil record
and in modern sediments.
River Canyon area of the Kubis platform in the deeply
dissected Zaris Mountains of south western
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.
Index fossil Examples of index fossils
Index fossils (also known as guide fossils, indicator fossils or zone
fossils) are fossils used to define and identify geologic periods (or
faunal stages). 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. The shorter the species' time range, the more precisely
different sediments can be correlated, and so rapidly evolving
species' fossils are particularly valuable. 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.
Cambrian trace fossils including
Rusophycus , made by a trilobite A coprolite of a carnivorous
dinosaur found in southwestern
Trace fossils consist mainly of tracks and burrows, but also include
coprolites (fossil feces ) and marks left by feeding. 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. Many traces date from significantly earlier
than the body fossils of animals that are thought to have been capable
of making them. 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 ).
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. They were first described by
William Buckland in 1829. Prior to this they were known as "fossil fir
cones " and "bezoar stones." They serve a valuable purpose in
paleontology because they provide direct evidence of the predation and
diet of extinct organisms. Coprolites may range in size from a few
millimetres to over 60 centimetres.
Transitional fossil Further information: List of
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. This is especially important where the descendant
group is sharply differentiated by gross anatomy and mode of living
from the ancestral group. 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. These fossils serve
as a reminder that taxonomic divisions are human constructs that have
been imposed in hindsight on a continuum of variation.
Microfossils about 1 mm Main article:
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. A commonly applied cutoff point
between "micro" and "macro" fossils is 1 mm. 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.
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.
Leptofoenus pittfieldae trapped in
Dominican amber , from 20 to 16 million years ago
Fossil resin (colloquially called amber ) is a natural polymer found
in many types of strata throughout the world, even the
Arctic . The
oldest fossil resin dates to the
Triassic , though most dates to the
Cenozoic . The excretion of the resin by certain plants is thought to
be an evolutionary adaptation for protection from insects and to seal
Fossil resin often contains other fossils called inclusions
that were captured by the sticky resin. These include bacteria, fungi,
other plants, and animals.
Animal inclusions are usually small
invertebrates , predominantly arthropods such as insects and spiders,
and only extremely rarely a vertebrate such as a small lizard.
Preservation of inclusions can be exquisite, including small fragments
Zombie taxon Eroded
Jurassic plesiosaur vertebral
centrum found in the Lower
Cretaceous Faringdon Sponge Gravels in
Faringdon, England. An example of a remanié fossil.
A derived, reworked or remanié fossil is a fossil found in rock that
accumulated significantly later than when the fossilized animal or
plant died. Reworked fossils are created by erosion exhuming
(freeing) fossils from the rock formation in which they were
originally deposited and their redeposition in an younger sedimentary
Petrified wood . The internal
structure of the tree and bark are maintained in the permineralization
process. Polished section of petrified wood showing annual
Fossil wood is wood that is preserved in the fossil record. Wood is
usually the part of a plant that is best preserved (and most easily
Fossil wood may or may not be petrified . 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 . 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 ).
Subfossil A subfossil dodo skeleton
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.
Subfossils are often found in caves or other shelters where they can
be preserved for thousands of years. 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. Additionally, isotope ratios can
provide much information about the ecological conditions under which
extinct animals lived. Subfossils are useful for studying the
evolutionary history of an environment and can be important to studies
in paleoclimatology .
Subfossils are often found in depositionary environments, such as
lake sediments, oceanic sediments, and soils. Once deposited, physical
and chemical weathering can alter the state of preservation.
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. Molecular fossils and isotope
ratios represent two types of chemical fossils. 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.
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 . Furthermore,
organic components (biosignatures ) that are often associated with
biominerals are believed to play crucial roles in both pre-biotic and
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 .
The search for evidence of habitability , taphonomy (related to
fossils ), and organic carbon on the planet
Mars is now a primary NASA
An example of a pseudofossil: Manganese dendrites on a limestone
bedding plane from
Solnhofen , Germany; scale in mm Main article:
Pseudofossils are visual patterns in rocks that are produced by
geologic processes rather than biologic processes. They can easily be
mistaken for real fossils. Some pseudofossils, such as dendrites , are
formed by naturally occurring fissures in the rock that get filled up
by percolating minerals. Other types of pseudofossils are kidney ore
(round shapes in iron ore) and moss agates , which look like moss or
plant leaves. 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.
HISTORY OF THE STUDY OF FOSSILS
History of paleontology See also: Timeline of
Gathering fossils dates at least to the beginning of recorded
history. The fossils themselves are referred to as the fossil record.
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 . Paleontologists examine the fossil record to understand the
process of evolution and the way particular species have evolved.
Many early explanations relied on folktales or mythologies. In China
the fossil bones of ancient mammals including
Homo erectus were often
mistaken for "dragon bones" and used as medicine and aphrodisiacs . In
the West fossilized sea creatures on mountainsides were seen as proof
of the biblical deluge .
In 1027, the Persian
Avicenna explained fossils' stoniness in The
Book of Healing :
If what is said concerning the petrifaction of animals and plants is
true, the cause of this (phenomenon) is a powerful mineralizing and
petrifying virtue which arises in certain stony spots, or emanates
suddenly from the earth during earthquake and subsidences, and
petrifies whatever comes into contact with it. As a matter of fact,
the petrifaction of the bodies of plants and animals is not more
extraordinary than the transformation of waters.
Aristotle realized that fossil seashells from rocks
were similar to those found on the beach, indicating the fossils were
once living animals.
Aristotle previously explained it in terms of
vaporous exhalations , which
Avicenna modified into the theory of
petrifying fluids (succus lapidificatus), later elaborated by Albert
of Saxony in the 14th century and accepted in some form by most
naturalists by the 16th century.
More scientific views of fossils emerged during the
Leonardo da Vinci
Leonardo da Vinci concurred with Aristotle's view that fossils were
the remains of ancient life. For example, da Vinci noticed
discrepancies with the biblical flood narrative as an explanation for
If the Deluge had carried the shells for distances of three and four
hundred miles from the sea it would have carried them mixed with
various other natural objects all heaped up together; but even at such
distances from the sea we see the oysters all together and also the
shellfish and the cuttlefish and all the other shells which congregate
together, found all together dead; and the solitary shells are found
apart from one another as we see them every day on the sea-shores.
And we find oysters together in very large families, among which some
may be seen with their shells still joined together, indicating that
they were left there by the sea and that they were still living when
the strait of Gibraltar was cut through. In the mountains of Parma and
Piacenza multitudes of shells and corals with holes may be seen still
sticking to the rocks...."
the 1834 Czech edition of Cuvier 's Discours sur les revolutions de la
surface du globe.
Robert Hooke (1635-1703) included micrographs of fossils in his
Micrographia and was among the first to observe fossil forams . 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.
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. He observed
that rocks from distant locations could be correlated based on the
fossils they contained. He termed this the principle of faunal
succession. This principle became one of Darwin's chief pieces of
evidence that biological evolution was real.
Georges Cuvier came to believe that most if not all the animal
fossils he examined were remains of extinct species. This led Cuvier
to become an active proponent of the geological school of thought
called catastrophism . Near the end of his 1796 paper on living and
fossil elephants he said: All of these facts, consistent among
themselves, and not opposed by any report, seem to me to prove the
existence of a world previous to ours, destroyed by some kind of
LINNAEUS AND DARWIN
Early naturalists well understood the similarities and differences of
living species leading Linnaeus to develop a hierarchical
classification system still in use today. Darwin and his
contemporaries first linked the hierarchical structure of the tree of
life with the then very sparse fossil record. Darwin eloquently
described a process of descent with modification, or evolution,
whereby organisms either adapt to natural and changing environmental
pressures, or they perish.
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
now known to be about 540 million years old. 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." Darwin also pondered the sudden appearance of many groups
(i.e. phyla ) in the oldest known
Cambrian fossiliferous strata.
Since Darwin's time, the fossil record has been extended to between
2.3 and 3.5 billion years. Most of these Precambrian fossils are
microscopic bacteria or microfossils . However, macroscopic fossils
are now known from the late Proterozoic. The
Ediacara biota (also
called Vendian biota) dating from 575 million years ago collectively
constitutes a richly diverse assembly of early multicellular
The fossil record and faunal succession form the basis of the science
of biostratigraphy or determining the age of rocks based on embedded
fossils. For the first 150 years of geology , biostratigraphy and
superposition were the only means for determining the relative age of
rocks. The geologic time scale was developed based on the relative
ages of rock strata as determined by the early paleontologists and
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.
Radiometric dating has shown that the earliest known stromatolites are
over 3.4 billion years old.
The fossil record is life's evolutionary epic that unfolded over
four billion years as environmental conditions and genetic potential
interacted in accordance with natural selection. The Virtual Fossil
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. Earth's deep time in the Proterozoic
and deeper still in the
Archean is only "recounted by microscopic
fossils and subtle chemical signals." 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. The
study of fossils, on the other hand, can more specifically pinpoint
when and in what organism a mutation first appeared.
paleontology work together in the clarification of science's still dim
view of the appearance of life and its evolution. Phacopid
trilobite Eldredgeops rana crassituberculata, the genus is named after
Crinoid columnals (Isocrinus nicoleti) from the
Carmel Formation at Mount Carmel Junction,
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
Devonian . 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. This and other data
Stephen Jay Gould and
Niles Eldredge to publish their seminal
paper on punctuated equilibrium in 1971.
X-ray tomographic analysis of early
embryonic microfossils yielded new insights of metazoan evolution at
its earliest stages. The tomography technique provides previously
unattainable three-dimensional resolution at the limits of
Fossils of two enigmatic bilaterians, the worm-like
Markuelia and a putative, primitive protostome , Pseudooides , provide
a peek at germ layer embryonic development. These 543-million-year-old
embryos support the emergence of some aspects of arthropod development
earlier than previously thought in the late Proterozoic. The preserved
Siberia underwent rapid diagenetic
phosphatization resulting in exquisite preservation, including cell
structures. 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. For example, the research suggests
Markuelia has closest
affinity to priapulid worms, and is adjacent to the evolutionary
Priapulida , Nematoda and Arthropoda .
TRADING AND COLLECTING
Fossil trading and
Fossil trading is the practice of buying and selling fossils. This is
many times done illegally with artifacts stolen from research sites,
costing many important scientific specimens each year. The problem is
quite pronounced in China, where many specimens have been stolen.
Fossil collecting (some times, in a non-scientific sense, fossil
hunting) is the collection of fossils for scientific study, hobby, or
Fossil collecting, as practiced by amateurs, is the
predecessor of modern paleontology and many still collect fossils and
study fossils as amateurs. Professionals and amateurs alike collect
fossils for their scientific value.
Three small ammonite fossils, each approximately 1.5 cm across
Eocene fossil fish Priscacara liops from the Green
River Formation of
A permineralized trilobite ,
Carcharodontosaurus teeth. The latter was found in the
Sahara Desert .
Fossil shrimp (
Petrified cone of
Araucaria mirabilis from
Patagonia , Argentina
dating from the
Jurassic Period (approx. 210 Ma )
A fossil gastropod from the
Cyprus . A serpulid worm is
Eocene fossil flower, collected August 2010 from Clare family fossil
quarry, Florissant, Colorado
A fairy loaf fossil, which is one of the most found fossils in the UK
Productid brachiopod ventral valve; Roadian, Guadalupian (Middle
Permian ); Glass Mountains, Texas.
Agatized coral from the
Hawthorn Group (
Florida . An example of preservation by replacement.
Fossils from beaches of the
Baltic Sea island of
Gotland , placed on
paper with 7 mm (0.28 inch) squares.
List of molluscan genera represented in the fossil record
* Schultz\'s rule
* ^ Oxford English Dictionary. Oxford University Press.
* ^ "theNAT :: San Diego Natural History Museum :: Your Nature
Connection in Balboa Park :: Frequently Asked Questions". Sdnhm.org.
Retrieved 5 November 2012.
* ^ Borenstein, Seth (13 November 2013). "Oldest fossil found: Meet
your microbial mom". Associated Press. Retrieved 15 November 2013.
* ^ Noffke, Nora; Christian, Christian; Wacey, David; Hazen, Robert
M. (8 November 2013). "Microbially Induced Sedimentary Structures
Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old
Dresser Formation, Pilbara, Western Australia" . Astrobiology . 13
Bibcode :2013AsBio..13.1103N. doi
:10.1089/ast.2013.1030 . PMC 3870916 . PMID 24205812 .
* ^ Brian Vastag (21 August 2011). "Oldest \'microfossils\' raise
hopes for life on Mars". The Washington Post. Retrieved 21 August
Wade, Nicholas (21 August 2011). "Geological Team Lays Claim to
Oldest Known Fossils". The New York Times. Retrieved 21 August 2011.
* ^ A B Borenstein, Seth (19 October 2015). "Hints of life on what
was thought to be desolate early Earth".
Excite . Yonkers, NY:
Mindspark Interactive Network .
Associated Press . Retrieved
* ^ A B Bell, Elizabeth A.; Boehnike, Patrick; Harrison, T. Mark;
et al. (19 October 2015). "Potentially biogenic carbon preserved in a
4.1 billion-year-old zircon" (PDF). Proc. Natl. Acad. Sci. U.S.A.
Washington, D.C.: National Academy of Sciences. 112: 14518–21. doi
:10.1073/pnas.1517557112 . ISSN 1091-6490 . PMC 4664351 . PMID
26483481 . Retrieved 2015-10-20. Early edition, published online
* ^ Westall, Frances; et al. (2001). "Early
Archean fossil bacteria
and biofilms in hydrothermally influenced sediments from the Barberton
greenstone belt, South Africa". Precambrian Research. 106 (1–2):
93–116. doi :10.1016/S0301-9268(00)00127-3 .
* ^ Shute, C. H.; Cleal, C. J. (1986). "Palaeobotany in museums".
Geological Curator. 4: 553–559.
* ^ Fields H (May 2006). "
Dinosaur Shocker - Probing a
68-million-year-old T. rex,
Mary Schweitzer stumbled upon astonishing
signs of life that may radically change our view of the ancient
beasts". Smithsonian Magazine. Archived from the original on
* ^ Schweitzer M H, Wittmeyer JL, Horner JR, Toporski JK;
Wittmeyer; Horner; Toporski (2005-03-25). "Soft-tissue vessels and
cellular preservation in Tyrannosaurus rex". Science. 307 (5717):
Bibcode :2005Sci...307.1952S. doi :10.1126/science.1108397 .
PMID 15790853 . CS1 maint: Multiple names: authors list (link )
* ^ Schweitzer M H, Zheng W, Cleland T P, Bern M; Zheng; Cleland;
Bern (January 2013). "Molecular analyses of dinosaur osteocytes
support the presence of endogenous molecules". Bone. 52 (1): 414–23.
doi :10.1016/j.bone.2012.10.010 . PMID 23085295 . CS1 maint: Multiple
names: authors list (link )
* ^ Embery G, Milner A C, Waddington R J, Hall R C, Langley M L,
Milan A M; Milner; Waddington; Hall; Langley; Milan (2003).
"Identification of Proteinaceous Material in the
Bone of the Dinosaur
Iguanodon" (PDF). Connective Tissue Research. 44(S1) (1): 41–6. doi
:10.1080/03008200390152070 . PMID 12952172 . CS1 maint: Multiple
names: authors list (link )
* ^ Schweitzer, M.H., W. Zheng, T.P. Cleland, M.B. Goodwin E.
Boatman, E. Theil, M.A. Marcus, and S.C. Fakra (Nov 2013). "A role for
iron and oxygen chemistry in preserving soft tissues, cells and
molecules from deep time" (PDF). Proceedings of the Royal Society. 281
(1774): 20132741. doi :10.1098/rspb.2013.2741 . PMC 3866414 . PMID
24285202 . CS1 maint: Uses authors parameter (link )
* ^ Zylberberg, L.; Laurin, M. (2011). "Analysis of fossil bone
organic matrix by transmission electron microscopy". Comptes Rendus
Palevol. 11 (5–6): 357–366. doi :10.1016/j.crpv.2011.04.004 .
* ^ Palmer, T. J.; Wilson, MA (1988). "Parasitism of Ordovician
bryozoans and the origin of pseudoborings". Palaeontology. 31:
* ^ A B Taylor, P. D. (1990). "Preservation of soft-bodied and
other organisms by bioimmuration: A review". Palaeontology. 33:
* ^ Wilson, MA; Palmer, T. J.; Taylor, P. D. (1994). "Earliest
preservation of soft-bodied fossils by epibiont bioimmuration: Upper
Ordovician of Kentucky". Lethaia. 27: 269–270. doi
* ^ A B Martin, M.W.; Grazhdankin, D.V.; Bowring, S.A.; Evans,
D.A.D.; Fedonkin, M.A.; Kirschvink, J.L. (5 May 2000). "Age of
Neoproterozoic Bilaterian Body and Trace Fossils, White Sea, Russia:
Implications for Metazoan Evolution". Science. 288 (5467): 841–5.
Bibcode :2000Sci...288..841M. doi :10.1126/science.288.5467.841 . PMID
10797002 . CS1 maint: Multiple names: authors list (link )
* ^ Pufahl, P.K.; Grimm, K.A.; Abed, A.M. & Sadaqah, R.M.Y.
(October 2003). "Upper
Cretaceous (Campanian) phosphorites in Jordan:
implications for the formation of a south Tethyan phosphorite giant".
Geology . 161 (3–4): 175–205. Bibcode
:2003SedG..161..175P. doi :10.1016/S0037-0738(03)00070-8 .
* ^ "Geologic Time: Radiometric Time Scale". U.S. Geological
Survey. Retrieved 20 September 2008.
* ^ Löfgren, A. (2004). "The conodont fauna in the Middle
Ordovician Eoplacognathus pseudoplanus Zone of Baltoscandia".
Geological Magazine. 141 (4): 505–524. doi
:10.1017/S0016756804009227 . Retrieved 17 November 2008.
* ^ Gehling, James; Jensen, Sören; Droser, Mary; Myrow, Paul;
Narbonne, Guy (March 2001). "Burrowing below the basal
Fortune Head, Newfoundland". Geological Magazine. 138 (2): 213–218.
doi :10.1017/S001675680100509X . Retrieved 17 November 2008.
* ^ e.g. Gehling, James; Jensen, Sören; Droser, Mary; Myrow, Paul;
Narbonne, Guy (March 2001). "Burrowing below the basal
Fortune Head, Newfoundland". Geological Magazine. 138 (2): 213–218.
doi :10.1017/S001675680100509X . Retrieved 17 November 2008.
* ^ Hug, L.A.; Roger, A.J. (2007). "The Impact of
Fossils and Taxon
Sampling on Ancient Molecular Dating Analyses". Molecular Biology and
Evolution. 24 (8): 889–1897. doi :10.1093/molbev/msm115 . PMID
* ^ Peterson, Kevin J.; Butterfield, N.J. (2005). "Origin of the
Eumetazoa: Testing ecological predictions of molecular clocks against
Proterozoic fossil record" . Proceedings of the National Academy
of Sciences. 102 (27): 9547–52.
Bibcode :2005PNAS..102.9547P. doi
:10.1073/pnas.0503660102 . PMC 1172262 . PMID 15983372 .
* ^ A B Prothero 2007 , pp. 50–53
* ^ Isaak, M (2006-11-05). "Claim CC200: There are no transitional
TalkOrigins Archive . Retrieved 30 April 2009.
* ^ Donovan, S. K. and Paul, C. R. C. (eds) 1998: The adequacy of
the fossil record, Wiley, New York, 312 pp.
* ^ Riding, R. (2007). "The term stromatolite: towards an essential
definition". Lethaia. 32 (4): 321–330. doi
* ^ "Stromatolites, the Oldest Fossils". Retrieved 4 March 2007.
* ^ A B Lepot, Kevin; Karim Benzerara, Gordon E. Brown, Pascal
Philippot (2008). "Microbially influenced formation of 2.7
Nature Geoscience . 1 (2): 118–21.
Bibcode :2008NatGe...1..118L. doi :10.1038/ngeo107 . CS1 maint:
Multiple names: authors list (link )
* ^ A B Allwood, Abigail; Grotzinger, Knoll, Burch, Anderson,
Coleman, and Kanik (2009). "Controls on development and diversity of
Archean stromatolites" . Proceedings of the National Academy of
Sciences. 106 (24): 9548–9555.
Bibcode :2009PNAS..106.9548A. doi
:10.1073/pnas.0903323106 . PMC 2700989 . PMID 19515817 . CS1 maint:
Multiple names: authors list (link )
Cradle of life: the discovery of earth's earliest fossils. Princeton,
N.J: Princeton University Press. 1999. pp. 87–89. ISBN 0-691-08864-0
. * ^ McMenamin, M. A. S. (1982). "Precambrian conical
stromatolites from California and Sonora". Bulletin of the Southern
California Paleontological Society. 14 (9&10): 103–105.
* ^ McNamara, K.J. (20 December 1996). "Dating the Origin of
Animals". Science. 274 (5295): 1993–1997. Bibcode
:1996Sci...274.1993M. doi :10.1126/science.274.5295.1993f . Retrieved
28 June 2008.
* ^ Awramik, S.M. (19 November 1971). "Precambrian columnar
stromatolite diversity: Reflection of metazoan appearance" (abstract).
Science. 174 (4011): 825–827.
Bibcode :1971Sci...174..825A. doi
:10.1126/science.174.4011.825 . PMID 17759393 . Retrieved 1 December
* ^ Bengtson, S. (2002). "Origins and early evolution of predation"
(PDF). In Kowalewski, M., and Kelley, P.H. The fossil record of
predation. The Paleontological Society Papers. 8. The Paleontological
Society. pp. 289–317. Retrieved 29 December 2014. CS1 maint: Uses
editors parameter (link )
* ^ Sheehan, P.M.; Harris, M.T. (2004). "Microbialite resurgence
after the Late
Ordovician extinction". Nature. 430 (6995): 75–78.
Bibcode :2004Natur.430...75S. doi :10.1038/nature02654 . PMID 15229600
. Retrieved 1 December 2007.
* ^ Riding R (March 2006). "Microbial carbonate abundance compared
with fluctuations in metazoan diversity over geological time" (PDF).
Sedimentary Geology. 185 (3–4): 229–38. Bibcode
:2006SedG..185..229R. doi :10.1016/j.sedgeo.2005.12.015 . Retrieved 9
* ^ Adams, E. W.; Grotzinger, J. P.; Watters, W. A.; Schröder, S.;
McCormick, D. S.; Al-Siyabi, H. A. (2005). "Digital characterization
of thrombolite-stromatolite reef distribution in a carbonate ramp
system (terminal Proterozoic, Nama Group, Namibia)" (PDF). AAPG
Bulletin. 89 (10): 1293–1318. doi :10.1306/06160505005 . Retrieved 8
* ^ "What is paleontology?". University of California Museum of
Paleontology. Retrieved 17 September 2008.
* ^ A B Fedonkin, M.A.; Gehling, J.G.; Grey, K.; Narbonne, G.M.;
Vickers-Rich, P. (2007). The Rise of Animals:
Diversification of the Kingdom Animalia. JHU Press. pp. 213–216.
ISBN 0-8018-8679-1 . Retrieved 14 November 2008.
* ^ e.g. Seilacher, A. (1994). "How valid is Cruziana
Stratigraphy?" (PDF). International Journal of Earth Sciences. 83 (4):
Bibcode :1994GeoRu..83..752S. doi :10.1007/BF00251073 .
Retrieved 9 September 2007.
* ^ "coprolites - Definitions from Dictionary.com".
* ^ Herron, Scott Freeman, Jon C. (2004). Evolutionary analysis
(3rd ed.). Upper Saddle River, NJ: Pearson Education. p. 816. ISBN
* ^ Derived fossil
"Reworked fossil" in Glossary of
Geology * ^ Ed Strauss (2001).
"Petrified Wood from Western Washington". Archived from the original
on 11 December 2010. Retrieved 8 April 2011.
* ^ Wilson Nichols Stewart; Gar W. Rothwell (1993).
the evolution of plants (2 ed.). Cambridge University Press. p. 31.
ISBN 978-0-521-38294-6 .
* ^ "Subfossils Collections". South Australian Museum. Archived
from the original on 2011-06-17. Retrieved 23 January 2014.
* ^ Chemical Fossils
* ^ The MEPAG Astrobiology Field Laboratory Science Steering Group
(26 September 2006). "Final report of the MEPAG Astrobiology Field
Laboratory Science Steering Group (AFL-SSG)" (.doc). In Steele,
Andrew; Beaty, David. The Astrobiology Field Laboratory. U.S.A.: Mars
Exploration Program Analysis Group (MEPAG) - NASA. p. 72. Retrieved
* ^ A B Grotzinger, John P. (24 January 2014). "Introduction to
Special Issue - Habitability, Taphonomy, and the Search for Organic
Carbon on Mars". Science . 343 (6169): 386–387. Bibcode
:2014Sci...343..386G. doi :10.1126/science.1249944 . PMID 24458635 .
Retrieved 24 January 2014.
* ^ A B Various (24 January 2014). "
Special Issue - Table of
Contents - Exploring Martian Habitability". Science . 343 (6169):
345–452. Retrieved 24 January 2014. CS1 maint: Uses authors
parameter (link )
* ^ Various (24 January 2014). "
Special Collection - Curiosity -
Exploring Martian Habitability". Science . Retrieved 24 January 2014.
CS1 maint: Uses authors parameter (link )
* ^ Grotzinger, J.P. et al. (24 January 2014). "A Habitable
Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars".
Science . 343 (6169): 1242777.
Bibcode :2014Sci...343A.386G. doi
:10.1126/science.1242777 . PMID 24324272 . Retrieved 24 January 2014.
CS1 maint: Uses authors parameter (link )
* ^ Alistair Cameron Crombie (1990). Science, optics, and music in
medieval and early modern thought. Continuum International Publishing
Group. pp. 108–109. ISBN 0-907628-79-6 .
* ^ Rudwick, M. J. S. (1985). The Meaning of Fossils: Episodes in
the History of Palaeontology.
University of Chicago Press . p. 24.
ISBN 0-226-73103-0 .
* ^ Earth\'s History, Paul R. Janke
* ^ da Vinci, Leonardo (1956) . The Notebooks of Leonardo Da Vinci.
London: Reynal & Hitchcock. p. 335. ISBN 0973783737 .
* ^ Bressan, David. "July 18, 1635:
Robert Hooke - The Last
Virtuoso of Silly Science". Scientific American Blog Network.
* ^ Georges Cuvier—
* ^ Darwin, C (1859) On the Origin of Species. Chapter 10: On the
Imperfection of the Geological Record.
* ^ Schopf JW (1999) Cradle of Life: The Discovery of the Earth's
Earliest Fossils, Princeton University Press, Princeton, NJ.
* ^ "The Virtual
Fossil Museum -
Fossils Across Geological Time and
Evolution". Retrieved 4 March 2007.
* ^ Knoll, A, (2003) Life on a Young Planet. (Princeton University
Press, Princeton, NJ)
* ^ Paul CRC and Donovan SK, (1998) An overview of the completeness
of the fossil record. in The Adequacy of the
Fossil Record (Paul CRC
and Donovan SK eds). 111–131 (John Wiley, New York).
Fortey, Richard , Trilobite!: Eyewitness to Evolution. Alfred
A. Knopf, New York, 2000.
* ^ Donoghue, PCJ; Bengtson, S; Dong, X; Gostling, NJ; Huldtgren,
T; Cunningham, JA; Yin, C; Yue, Z; Peng, F; et al. (2006).
X-ray tomographic microscopy of fossil embryos". Nature.
442 (7103): 680–683.
Bibcode :2006Natur.442..680D. doi
:10.1038/nature04890 . PMID 16900198 . CS1 maint: Explicit use of et
al. (link )
* ^ Milmo, Cahal (2009-11-25). "
Fossil theft: One of our dinosaurs
is missing". The Independent. London. Retrieved 2 May 2010.
Simons, Lewis. "
Fossil Wars". National Geographic. The National
Geographic Society .
Willis, Paul; Clark, Tim; Dennis, Carina (18 April 2002). "Fossil
Trade". Catalyst. CS1 maint: Multiple names: authors list (link )
Farrar, Steve (5 November 1999). "
Cretaceous crimes that fuel the
fossil trade". Times Higher Education. Retrieved 2 November 2011. *
^ "Global Times -
Fossil trade puts China\'s natural history at
risk". Archived from the original on 24 November 2010.
* It\'s extremely hard to become a fossil, by
Olivia Judson , The
New York Times
* Bones Are Not the Only Fossils, by
Olivia Judson , The New York
The Wikibook Historical
Geology has a page on the topic of: FOSSILS
The Wikibook Historical
Geology has a page on the topic of: FOSSILS
AND ABSOLUTE DATING