Throughout human history, civilization have uncovered fossils and also wondered around the creatures that lived lengthy ago. In old times, fossils motivated legends the monsters and also other strange creatures. The Chinese writer Chang Qu reports the exploration of “dragon bones”, i m sorry were most likely dinosaur fossils in China 2,000 years ago. The griffin, a mythical creature through a lion’s body and an eagle’s head and wings, to be probably based on skeletons of Protoceratops that were uncovered by wanderers in central Asia (Figure 11.1).

You are watching: Fossil formed when an outline of the original organism is formed from left-over carbon


*

*

Figure 11.1: Griffin (left) and Protoceratops (right).

Another fossil reminded the Greeks the the coiled horns of a ram. The Greeks named them ammonites ~ the ram god Ammon. Similarly, legends of the Cyclops might be based on fossilized elephant skulls found in Crete and also other Mediterranean islands. Deserve to you check out why (Figure 11.2)?


*

*

Figure 11.2: Ammonite (left) and elephant skull (right).

Many of the real creatures who bones became fossilized to be no less marvelous 보다 the mythical creatures they motivated (Figure 11.3). The gigantic pterosaur Quetzalcoatlus had a wingspan of up to 12 meter (39 feet). The dinosaur Argentinosaurus had an approximated weight of 80,000 kg, equal to the weight of 7 elephants! various other fossils, such as the trilobite and ammonite, admire us with their bizarre forms and delicate beauty.


*

Figure 11.3: Kolihapeltis sp (left) and Ammonite (right).

Lesson Objectives

Explain why that is rarely for an biology to be maintained as a fossil.Distinguish in between body fossils and also trace fossils.Describe five species of fossilization.Explain the importance of table of contents fossils, and also give numerous examples.Describe what a living fossil is.

How Fossils Form

fossil is any remains or trace of an old organism. Fossils include body fossils, left behind as soon as the soft parts have decayed away, too as trace fossils, such as burrows, tracks, or fossilized garbage (feces) (Figure 11.4).


Figure 11.4: Coprolite (fossilized garbage or feces) from a meat-eating dinosaur.
The procedure of a once living organism coming to be a fossil is called fossilization. Fossilization is a really rare process: of all the biology that have lived ~ above Earth, just a tiny percent of castle ever end up being fossils. To watch why, imagine an antelope that dies on the african plain. Many of its body is quickly eaten by scavengers, and also the continuing to be flesh is soon consumed by insects and also bacteria, leave behind only scattered bones. As the years go by, the bones are scattered and fragmented into little pieces, eventually transforming into dust and returning their nutrients to the soil. It would certainly be rarely for any of the antelope’s remains to in reality be preserved as a fossil.


Figure 11.5: Fossil covering that has been struck by a boring sponge.
On the s floor, a similar procedure occurs as soon as clams, oysters, and other shellfish die. The soft parts easily decay, and also the shells space scattered over the sea floor. If the shells space in shallow water, wave action soon grinds them into sand-sized pieces. Even if they space not in shallow water, the shells are struck by worms, sponges, and also other pets (Figure 11.5).

For pets that lack tough shells or bones, fossilization is even an ext rare. Together a result, the fossil record includes many pets with shells, bones, or other hard parts, and couple of softbodied organisms. There is practically no fossil document of jellyfish, worms, or slugs. Insects, which are by much the most typical land animals, are only rarely discovered as fossils. Due to the fact that mammal teeth room much more resistant than other bones, a big portion the the mammal fossil record is composed of teeth. This means the fossil record will show many organisms that had shells, bones or other difficult parts and also will almost always miss out on the many soft-bodied organisms that lived at the exact same time.

Because many decay and also fragmentation occurs at the surface, the main factor that contributes come fossilization is quick burial. Marine animals that die near a river delta might be buried by sediment carried by the river. A storm in ~ sea may shift sediment on the ocean floor, covering and helping to preserve skeletal remains.

On land, interment is rare, so subsequently fossils of land animals and plants space less usual than marine fossils. Floor organisms can be hidden by mudslides or ash native a volcano eruption, or covered by sand in a sandstorm. Skeletons have the right to be covered by dirt in lakes, swamps, or bogs as well. Some of the best-preserved skeletons that land pets are found in the La Brea Tar Pits the Los Angeles, California. Return the pets trapped in the pits probably suffered a slow, miserable death, your bones were maintained perfectly through the sticky tar.

In despite the of the difficulties of preservation, billions of fossils have been discovered, examined, and also identified by thousands of scientists. The fossil record is our best clue to the background of life ~ above Earth, and an important indicator of previous climates and also geological conditions as well. The fossil record also plays a an essential role in our lives. Fossil fuels such as coal, gas, and also oil formed from the decayed stays of plants and also animals the lived numerous years ago.


Types that Fossils

Fossilization can happen in numerous ways. Most fossils are kept in one of five processes (Figure 11.6): preserved remains, permineralization, molds and also casts, replacement, and also compression.

Preserved Remains

The rarest kind of fossilization is the preservation of initial skeletal material and even soft tissue. Because that example, insects have been preserved perfectly in amber, i beg your pardon is old tree sap. Several mammoths and even a Neanderthal hunter have been uncovered frozen in glaciers. These maintained remains allow scientists the rare opportunity to study the skin, hair, and organs of ancient creatures. Researchers have accumulated DNA from these remains and also compared the DNA sequences to those of contemporary creatures.

Permineralization

The many common method of fossilization is permineralization. After a bone, timber fragment, or covering is buried in sediment, it might be exposed come mineral-rich water the moves v the sediment. This water will deposit minerals right into empty spaces, developing a fossil. Fossil dinosaur bones, petrified wood, and many marine fossils were created by permineralization.

Molds and also Casts

In some cases, the initial bone or shell dissolves away, leaving behind an empty an are in the shape of the covering or bone. This depression is called a mold. Later on the space may be filled with other sediments to type a matching cast in the form of the initial organism. Many mollusks (clams, snails, octopi and squid) are typically found together molds and casts since their shells dissolve easily.

Replacement

In some cases, the original shell or bone dissolves away and is changed by a different mineral. Because that example, shells the were initially calcite might be changed by dolomite, quartz, or pyrite. If quartz fossils space surrounded through a calcite matrix, the calcite can be dissolved away by acid, leaving behind one exquisitely maintained quartz fossil.

Compression

Some fossils form when their stays are compressed by high pressure. This can leave behind a dark imprint the the fossil. Compression is most usual for fossils that leaves and also ferns, however can occur with various other organisms, together well.

*

Figure 11.6: Five types of fossils: insect maintained in amber, petrified wood, cast and mold the a clam shell, compression fossil of a fern and also pyritized ammonite.

Exceptional Preservation

Some rock bed have produced exceptional fossils. Fossils indigenous these beds may display evidence that soft body parts that room not generally preserved. 2 of the many famous instances of soft organism preservation are the burgess Shale in Canada and also the Solnhofen Limestone in Germany. The citizen Shale is 505 million year old and records the first explosion that shelled biology in Earth’s oceans. Countless of the citizen Shale fossils are bizarre animals that seem unrelated to any other animal group. The Solnhofen Limestone is 145 million year old and contains fossils of numerous soft-bodied biology that space not generally preserved, such as jellyfish. The most famous Solnhofen fossil is Archaeopteryx, among the earliest birds. Return it each other a dinosaur fossil, impressions of feather can plainly be watched (Figure 11.7).


Figure 11.7: Fossils native Lagerstätten: Archaeopteryx (left) and Anomalocaris (right). Archaeopteryx was very early bird. Anomalocaris was an massive predator (one meter long) that lived 500 million years ago.

Index Fossils and Living Fossils

The fossil record shows clearly that end time, life on earth has changed. Fossils in relatively young rocks often tend to resemble animals and also plants that space living today. In larger rocks, fossils space less similar to modern organisms.

As scientists gathered fossils from different rock layers and also formations, they discovered that they could often identify the rock layer by the assemblage that fossils it contained. Some fossils proved particularly useful in matching up rock layers from various regions. This fossils, calledindex fossils, are widespread yet only existed for a fairly brief period of time. When a specific index fossil is found, the relative period of the bed is instantly known.

Many fossils may qualify as index fossils. Ammonites, trilobites, and also graptolites are regularly used as index fossils, as room various microfossils, or fossils of microscopic organisms. Fossils of pets that drifted in the top layers that the ocean are an especially useful together index fossils, together they might be dispersed all over the world.

In contrast to table of contents fossils, living fossils are organisms that have actually existed for a exponentially long duration of time without transforming very much at all. For example, the Lingulata brachiopods have dated the Cambrian period to the present, a time expectancy of end 500 million years! modern-day specimens that Lingulata are practically indistinguishable from their fossil counterparts (Figure 11.8).


Figure 11.8: Fossil Lingula (left) and also modern Lingula (right).

Clues from Fossils

Fossils space our best form of evidence about the history of life top top Earth. In addition, fossils can provide us clues about past climates, the activities of plates, and also other major geological events.

The very first clue that fossils can provide is whether an environment was marine (underwater) or terrestrial (on land). In addition to the rock characteristics, fossils deserve to indicate whether the water was shallow or deep, and also whether the price of sedimentation was slow-moving or rapid. The amount of wear and fragmentation the a fossil can allow scientists to estimate the amount of wave activity or the frequency of storms.

Often fossils of maritime organisms are discovered on or near tall mountains. For example, the Himalayas, the tallest mountains in the world, save on computer trilobites, brachiopods, and also other naval fossils. This shows that rocks top top the seabed have been uplifted to type huge mountains. In the situation of the Himalayas, this happened when the Indian Subcontinent began to ram right into Asia about 40 million years ago.

Fossils can additionally reveal clues about past climate. Because that example, fossils that plants and coal beds have been found in Antarctica. Back Antarctica is frozen today, in the previous it must have been much warmer. This happened both since Earth’s climate has changed and due to the fact that Antarctica has actually not always been located at the south Pole.

One the the many fascinating trends revealed through the fossil record is a number of mass extinctions, times as soon as many types died off. Back the mass extinction that eliminated the dinosaurs is many famous, the biggest mass extinction in Earth history occurred in ~ the end of the Permian period, around 250 million year ago. In this catastrophe, that is estimated that end 95% of species on planet went extinct! The reason of this mass extinctions is not absolutely known, however most scientists believe that collisions through comets or asteroids to be the cause of at least a couple of of these disasters.

Lesson Summary

A fossil is any remains of ancient life. Fossils deserve to be human body fossils, i beg your pardon are continues to be of the organism chin or trace fossils, such together burrows, tracks, or other proof of activity.Preservation as a fossil is a fairly rare process. The possibilities of ending up being a fossil are amplified by quick burial and also the visibility of preservable hard parts, such together bones or shells.Fossils type in 5 ways: preservation of original remains, permineralization, molds and also casts, replacement, and compression.Rock formations with impressive fossils room called very important for scientists to study. They permit us to see information around organisms the we might not otherwise ever know.Index fossils space fossils that room widespread yet only existed for a short duration of time. Index fossils aid scientists to uncover the relative age of a rock layer and also match it increase with various other rock layers.Living fossils are organisms the haven’t readjusted much in countless years and are still alive today.Fossils give clues around the background of life on Earth, environments, climate, movement of plates, and also other events.

See more: Which Is The Graph Of A Quadratic Equation That Has A Negative Discriminant?

Review Questions

What factors make it much more likely the an pet will be maintained as a fossil?What are the 5 main procedures of fossilization?A scientist wants to determine the age of a rock. The rock has an index fossil and an ancient relative of a living fossil. Which fossil will be much more useful for dating the rock, and also why?The island that Spitzbergen is in the Arctic ocean north of Norway, close to the phibìc Pole. Fossils of tropical fruits have actually been discovered in charcoal deposits in Spitzbergen. What go this indicate?

Vocabulary

amberFossilized tree sap.body fossilThe continues to be of an ancient organism. Examples include shells, bones, teeth, and leaves.castA structure that forms when sediments to fill a mold and also harden, creating a replica the the original structure.fossilAny remains or map of an old organism.fossil fuelA fuel the was created from the remains of ancient organisms. Examples encompass coal, oil, and natural gas.fossilizationThe process of coming to be a fossil.index fossilA fossil that identifies and shows the relative age of the rocks in which it is found. Index fossils come from species that were widespread yet existed for a fairly brief duration of time.living fossilA modern-day species or genus that has existed on earth for numerous years without an altering very much.marineOf or belonging come the sea.mass extinctionA duration of time when an abnormally high number of species ended up being extinct.microfossilA fossil that should be studied through the assist of a microscope.moldAn impression made in sediments by the hard parts of an organism.permineralizationA type of fossilization in i m sorry minerals room deposited right into the pores of the original tough parts of an organism.terrestrialOf or belonging come the land.trace fossilEvidence that the activity of an ancient organism. Examples include tracks, trails, burrows, tubes, boreholes, and bite marks.

Points come Consider

What room some other examples of mythical creatures that may be based upon fossils?Why is that so rare for an pet to be kept as a fossil?Some biology are more easily preserved than others. Why is this a trouble for scientists who space studying old ecosystems?Why are examples of remarkable fossil preservation so valuable for scientists?Many fossils of maritime organisms have been discovered in the center of continents, much from any ocean. What conclusion have the right to you attract from this?