Throughout person history, human being have found fossils and also wondered about the creatures that lived lengthy ago. In old times, fossils motivated legends of monsters and other strange creatures. The Chinese writer Chang Qu reports the exploration of “dragon bones”, i beg your pardon were most likely dinosaur fossils in China 2,000 years ago. The griffin, a mythical creature v a lion’s body and an eagle’s head and wings, was probably based on skeletons of Protoceratops that were uncovered by nomads in main Asia (Figure 11.1).

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

Another fossil reminded the Greeks the the coiled horns that a ram. The Greeks called them ammonites after ~ the lamb god Ammon. Similarly, legends the the Cyclops may be based upon fossilized elephant skulls uncovered in Crete and other Mediterranean islands. Can you view why (Figure 11.2)?



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

Many of the genuine creatures who bones became fossilized to be no much less marvelous 보다 the mythical creatures they motivated (Figure 11.3). The large pterosaur Quetzalcoatlus had a wingspan of approximately 12 meter (39 feet). The dinosaur Argentinosaurus had an approximated weight that 80,000 kg, equal to the load of seven elephants! various other fossils, such together the trilobite and also ammonite, admire us through their bizarre forms and also delicate beauty.


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

Lesson Objectives

Explain why that is rare for an organism to be kept as a fossil.Distinguish between body fossils and trace fossils.Describe five species of fossilization.Explain the prestige of index fossils, and give several examples.Describe what a life fossil is.

How Fossils Form

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

Figure 11.4: Coprolite (fossilized garbage or feces) native a meat-eating dinosaur.
The procedure of a as soon as living organism becoming a fossil is called fossilization. Fossilization is a very rare process: of every the biology that have lived top top Earth, only a tiny portion of them ever end up being fossils. To watch why, imagine one antelope that dies on the african plain. Many of its body is conveniently eaten by scavengers, and the staying flesh is soon consumed by insects and also bacteria, leave behind just scattered bones. Together the years walk by, the bones space scattered and also fragmented into small pieces, eventually turning into dust and returning their nutrient to the soil. It would certainly be rare for any type of of the antelope’s remains to actually be preserved as a fossil.

Figure 11.5: Fossil covering that has been assaulted by a boring sponge.
On the s floor, a similar process occurs when clams, oysters, and also other shellfish die. The soft parts easily decay, and the shells are scattered end the sea floor. If the shells are in shallow water, wave action soon grinds them right into sand-sized pieces. Also if they are not in shallow water, the shells are attacked by worms, sponges, and also other animals (Figure 11.5).

For pets that lack tough shells or bones, fossilization is even more rare. As a result, the fossil record contains many animals with shells, bones, or other hard parts, and few softbodied organisms. Over there is practically no fossil record of jellyfish, worms, or slugs. Insects, which space by far the most common land animals, are only rarely found as fossils. Since mammal teeth space much much more resistant than other bones, a huge portion that the mammal fossil record consists of teeth. This way the fossil document will show many organisms that had shells, bones or other hard parts and will virtually always miss out on the plenty of soft-bodied biology that live at the exact same time.

Because many decay and also fragmentation wake up at the surface, the main element that contributes come fossilization is fast burial. Marine pets that die close to a river delta may be hidden by sediment carried by the river. A storm at sea may shift sediment on the ocean floor, covering and helping to preserve skeletal remains.

On land, interment is rare, so consequently fossils of soil animals and also plants room less usual than naval fossils. Land organisms have the right to be hidden by mudslides or ash native a volcanic eruption, or spanned by sand in a sandstorm. Skeletons deserve to be extended by dirt in lakes, swamps, or bogs together well. Few of the best-preserved skeletons the land animals are found in the La Brea Tar Pits that Los Angeles, California. Although the pets trapped in the pits more than likely suffered a slow, miserable death, their bones were kept perfectly by the difficult tar.

In spite of the obstacles of preservation, billions of fossils have actually been discovered, examined, and also identified by thousands of scientists. The fossil record is our best clue come the history of life top top Earth, and an essential indicator of past climates and geological conditions as well. The fossil record also plays a key role in our lives. Fossil fuels such as coal, gas, and oil created from the decayed stays of plants and animals that lived millions of years ago.

Types the Fossils

Fossilization can happen in numerous ways. Most fossils are kept in one of 5 processes (Figure 11.6): maintained remains, permineralization, molds and casts, replacement, and also compression.

Preserved Remains

The rarest kind of fossilization is the conservation of original skeletal material and also even soft tissue. For example, insects have actually been kept perfectly in amber, i m sorry is ancient tree sap. Number of mammoths and also even a Neanderthal hunter have been found frozen in glaciers. These kept remains permit scientists the rare opportunity to study the skin, hair, and organs of ancient creatures. Scientists have built up DNA from this remains and compared the DNA sequences come those of modern creatures.


The most common technique of fossilization is permineralization. After a bone, timber fragment, or shell is hidden in sediment, it might be exposed to mineral-rich water the moves v the sediment. This water will certainly deposit minerals right into empty spaces, creating a fossil. Fossil dinosaur bones, petrified wood, and many marine fossils were developed by permineralization.

Molds and Casts

In some cases, the initial bone or shell dissolves away, leaving behind an empty space in the shape of the covering or bone. This depression is referred to as a mold. Later the space may it is in filled with other sediments to type a matching cast in the shape of the initial organism. Numerous mollusks (clams, snails, octopi and also squid) are generally found as molds and also casts because their shells dissolve easily.


In some cases, the initial shell or bone disappear away and also is replaced by a different mineral. Because that example, shells that were originally calcite might be changed by dolomite, quartz, or pyrite. If quartz fossils space surrounded through a calcite matrix, the calcite can be liquified away through acid, leave behind an exquisitely preserved quartz fossil.


Some fossils type when their continues to be are compressed by high pressure. This have the right to leave behind a dark imprint the the fossil. Compression is most usual for fossils the leaves and ferns, but can happen with other organisms, as well.


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

Exceptional Preservation

Some rock bed have produced exceptional fossils. Fossils native these beds may present evidence the soft body components that are not generally preserved. 2 of the most famous examples of soft organism conservation are the citizen Shale in Canada and also the Solnhofen Limestone in Germany. The citizen Shale is 505 million years old and also records the first explosion the shelled organisms in Earth’s oceans. Numerous of the burgess Shale fossils space bizarre pets that it seems ~ unrelated to any kind of other animal group. The Solnhofen Limestone is 145 million years old and also contains fossils of numerous soft-bodied biology that are not generally preserved, such together jellyfish. The most famed Solnhofen fossil is Archaeopteryx, one of the faster birds. Although it each other a dinosaur fossil, impressions of feather can plainly be seen (Figure 11.7).

Figure 11.7: Fossils indigenous Lagerstätten: Archaeopteryx (left) and Anomalocaris (right). Archaeopteryx was an early bird. Anomalocaris was an enormous predator (one meter long) that lived 500 million year ago.

Index Fossils and also Living Fossils

The fossil record shows clearly that over time, life on earth has changed. Fossils in fairly young rocks tend to resemble animals and plants that space living today. In enlarge rocks, fossils room less similar to modern organisms.

As scientists gathered fossils from various rock layers and formations, they uncovered that they might often acknowledge the rock layer by the assemblage of fossils that contained. Part fossils proved specifically useful in matching up absent layers from various regions. These fossils, calledindex fossils, space widespread but only existed for a relatively brief period of time. As soon as a certain index fossil is found, the relative period of the bed is immediately known.

Many fossils may qualify together index fossils. Ammonites, trilobites, and 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 particularly useful together index fossils, as they may be dispersed all end the world.

In contrast to table of contents fossils, living fossils are biology that have actually existed because that a significantly long period of time without transforming very much at all. For example, the Lingulata brachiopods have existed from the Cambrian period to the present, a time expectancy of over 500 million years! modern specimens that Lingulata are practically indistinguishable from your fossil counterparts (Figure 11.8).

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

Clues from Fossils

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

The an initial clue that fossils can give is even if it is an environment was marine (underwater) or terrestrial (on land). Together with the absent characteristics, fossils deserve to indicate even if it is the water to be shallow or deep, and whether the rate of sedimentation was slow-moving or rapid. The amount of wear and also fragmentation the a fossil can permit scientists to calculation the amount of wave activity or the frequency of storms.

Often fossils of naval organisms are discovered on or near tall mountains. For example, the Himalayas, the tallest mountains in the world, contain trilobites, brachiopods, and also other marine fossils. This indicates that rocks top top the seabed have been uplifted to form huge mountains. In the instance of the Himalayas, this occurred when the Indian Subcontinent began to ram right into Asia around 40 million years ago.

Fossils can additionally reveal clues about past climate. For example, fossils of plants and coal beds have actually been uncovered in Antarctica. Back Antarctica is frozen today, in the previous it must have actually been lot warmer. This occurred both because Earth’s climate has changed and due to the fact that Antarctica has not always been situated at the south Pole.

One the the many fascinating trends revealed by the fossil record is a number of mass extinctions, times when many varieties died off. Back the fixed extinction that killed the dinosaurs is most famous, the biggest mass extinct in Earth background occurred in ~ the finish of the Permian period, around 250 million year ago. In this catastrophe, the is estimated that over 95% of species on earth went extinct! The reason of these mass extinctions is not definitely known, yet most scientists believe that collisions with comets or asteroids to be the reason of at least a couple of of these disasters.

Lesson Summary

A fossil is any kind of remains of old life. Fossils deserve to be body fossils, i beg your pardon are continues to be of the organism chin or trace fossils, such as burrows, tracks, or other evidence of activity.Preservation as a fossil is a relatively rare process. The opportunities of ending up being a fossil are enhanced by quick burial and also the existence of preservable hard parts, such together bones or shells.Fossils type in five ways: conservation of original remains, permineralization, molds and also casts, replacement, and also compression.Rock formations with exceptional fossils space called very important for scientists to study. They permit us to view information around organisms that we might not otherwise ever know.Index fossils are fossils that room widespread but only existed because that a short period of time. Table of contents fossils help scientists to uncover the relative period of a absent layer and match it increase with various other rock layers.Living fossils are organisms the haven’t readjusted much in numerous years and are still lively today.Fossils provide clues around the background of life on Earth, environments, climate, activity of plates, and other events.

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Review Questions

What factors make it an ext likely the an animal will be kept as a fossil?What space the five main procedures of fossilization?A scientist wants to recognize the period of a rock. The rock includes an table of contents fossil and an ancient relative of a living fossil. I beg your pardon fossil will be more useful for dating the rock, and why?The island of Spitzbergen is in the Arctic s north of Norway, near the north Pole. Fossils that tropical fruits have been uncovered in coal deposits in Spitzbergen. What walk this indicate?


amberFossilized tree sap.body fossilThe continues to be of an old organism. Examples encompass shells, bones, teeth, and also leaves.castA structure that develops when sediments to fill a mold and also harden, forming a replica of the initial structure.fossilAny continues to be or map of an old organism.fossil fuelA fuel that was developed from the continues to be of old organisms. Examples incorporate coal, oil, and also natural gas.fossilizationThe process of ending up being a fossil.index fossilA fossil that identifies and shows the relative period of the rocks in which the is found. Index fossils come from types that to be widespread but existed for a relatively brief duration of fossilA modern-day species or genus that has actually existed on planet for millions of years without changing very much.marineOf or belonging come the sea.mass extinctionA period of time when an uncommonly high number of species became extinct.microfossilA fossil that must be studied through the aid of a microscope.moldAn impression do in sediments by the difficult parts of one organism.permineralizationA kind of fossilization in which minerals are deposited into the pores that the original hard parts of one organism.terrestrialOf or belonging to the land.trace fossilEvidence the the activity of an ancient organism. Examples include tracks, trails, burrows, tubes, boreholes, and bite marks.

Points come Consider

What space some other instances of mythical creatures that might be based upon fossils?Why is the so rare for an pet to be kept as a fossil?Some organisms are more easily preserved than others. Why is this a difficulty for researchers who room studying ancient ecosystems?Why are instances of remarkable fossil conservation so beneficial for scientists?Many fossils of naval organisms have actually been found in the center of continents, far from any ocean. What conclusion can you attract from this?