It is a bit difficult to define precisely the word fossil. This word is derived from the Latin verb ” fodere “ which means to dig . Therefore, we could basically say that a fossil means anything that is extracted from the earth . At present, however, fossils are limited to referring to organic remains that are obtained from the earth and exclude inorganic objects or objects created by humans. In a popular sense, a fossil can be defined as footprints of nature in the belly of the earth.. A fossil includes the remains of a complete organism or some part of an organism or in other cases direct evidence of the previous existence of some organism in the sediments of the earth .


What are fossils?

Fossils are the remains or different marks of animals that are already extinct and that after their deaths, the marks of their activities have been preserved over time in some way.

  • Characteristics of the fossils
  • History
  • What are they for
  • Types of fossils
  • Where they are
  • Training
  • Conservation
  • What is the science that studies fossils
  • What material are they made of
  • Importance
  • Examples of fossils

Characteristics of the fossils

The most representative characteristics that we can observe in the fossils are the following:

  • To be considered a fossil, it must belong to a geological age prior to the current one that is older than 11 thousand years .
  • Depending on their conservation, remains that are less than 11 thousand years old are classified as sub fossils .
  • They are formed only in sedimentary areas , because during the sedimentation process of rocks, fossilization occurs.
  • In general, the hardest parts, such as bones and teeth , are more easily preserved in fossils over time.
  • Commonly, fossils can be found in rocks , ice , tree sap that ran in the logs.
  • It can be formed from any animal but the most common are vertebrate animals that have a bone structure that manages to overcome decomposition after death.
  • They can also be made up of tracks or marks that have been left by the animal.


Throughout history, man has lived with fossils from different organisms that have been interpreted in today . Many myths and legends have been formed from them creating a series of magical stories and have been the subject of scientific controversy in many cases. In a cave many gastropods and fossil corals were found that belonged to the Neanderthals , who inhabited the cave. In the Neolithic , in Egypt , metal fossils were found. The Achaeans, Ancient GreeksThey also discovered remains similar to those of a human being in a cave located on Etna . Throughout the centuries, as we can see, mythical beings , giants and monsters have been related to the fossil remains. This situation was maintained until the beginning of the last century, when the British geologist Lyell gave a definition to fossils as remains of organisms that inhabited in other times which were integrated into the sedimentary rocks .

What are they for

Fossils serve us because of the great information they provide us. They serve to reconstruct ecosystems and conditions of climate past, are paleo environmental indicators. They also help us to recreate palaeogeographic constructions and have allowed us to know the origin of many of the animals that we observe today.

Types of fossils

There are in the area of paleontology , two different types of fossils that can be studied, these are:

  • Somatofossils : in this group we can find all those fossils that attract the most attention because they are formed by parts of the body of a living being that is already extinct . In this group we can find teeth, shells, shells, bones, leaves and trunks.
  • Icnofossils : this type of fossil is composed of a series of signs that show that a living being was or lived in a certain place. In this group we find the tracks, eggshells, excrements that have managed to be preserved through mineralization , shelters of life or caves where the animals under study existed.

Where they are

Actually a fossil can be found anywhere in the world, but there are some places on earth that are rich in fossils, such as the Burgess Shale located in Canada and the Solnhofen limestone in Patagonia . They have also been located in Spain , where deposits originating from the Pleistocene have been found .


Fossils, somatofossils, ichnofossils, can be fossilized through three different ways that are mineralization , smelting and molding and carbonization , processes that preserve the remains for millions of years.


In this process, bones and ichnofossils are formed . The remains of the body obtain more minerals or there is an alteration in those that already exist in the bone , which turn them into remains equal to a rock , a process called petrification . This process can occur through two different mechanisms that are:

  • Recrystallization : The original organism is not preserved in its original material and can be replaced by some other mineral, so the structure or shape of the fossil is partially modified.
  • Epigenization : it occurs in two different ways. One is permineralization and it originates when the original material that the body has undergoes a sum of minerals that penetrate the bone. The second process is called pseudomorphosis , and in this process the original form of the organism is maintained but its material is exchanged for another mineral.


This process occurs when oxygen , hydrogen and nitrogen are lost mainly, which produces a carbon film . It is usual in structures made of lignin , chitin , cellulose or keratin . It happens when plant or animal remains are crushed by a rock.

Foundry and Molds

They are negative impressions that do not represent the organism as it is, or positive that represents the organism as it really is, in other words a copy, of parts that an ichnofossil organism has. These molds can be formed in three different ways:

  • Exterior : forms a negative impression of the organism . The body is externally covered by a type of material and its body is left in mud that turns into rock .
  • Interior : creates an internal impression of the organism, usually in shells . The mold is negative and is formed when mud or other material penetrates inside the holes and into the rest of the animal and it ends up solidifying .
  • Against mold: it forms a copy of the original organism that is filled with some material and forms a copy of the organism that formed the “first mold” . A common example of this type is the carbon footprint .

Among the types of fossil formation we can also find mummification that preserves the organism practically as it was in life.


For the correct conservation of a fossil, the following steps must be followed: 

Marking and labeling

They must be kept well labeled and the species and information about the place where it was found must be placed on the label . A number can be assigned by painting a small white spot on the fossil.

Small fossils

Smaller fossils are prepared on an excavated slide, which is a piece of glass used in microscopy. The fossil labels should be glued directly to the slide.


Naturalist boxes can be used for small collections. In paleontology laboratories, fossils are kept in cupboards with drawers, shelves with boxes, etc.

What is the science that studies fossils

The science that is responsible for carrying out studies of fossils is known by the name of paleontology, which in addition to studying them, describes and analyzes them to detail and interpret the biological factors and characteristics that species have had in past times. This science has various foundations and knowledge of geology and biology . These studies help us to know and understand aspects of the origin and evolution of life on the face of the earth and can also include geographical , ecological , chemical andclimatological .

What material are they made of

The formation of the fossil will depend on the chemical composition of a certain organism and the composition of water to which it is exposed. Many of the fossils contain free lipids such as carbohydrates , proteins , chitin and lignin,  and many have kerogen as their main component . Animals that have a shell are easier to preserve as fossils.


The study of fossils is very important because it provides us with a vision of past life as well as the structure , distribution and reproductive characteristics of living beings. This helps us better understand and appreciate the way flora and fauna interact today . It is important for science in general, for geology because it provides information about the history of the planet, it is a basis for the formulation of different evolutionary theories , it helps to rebuild the ecosystems where fossils have been found to know the different conditions of theclimate that have existed in a certain region and finally, the fuel we use daily comes from fossils, and thanks to them we have electricity and transportation .

Examples of fossils

Some examples of important fossils that have been found are:

  • Metaspriggina : considered the oldest known fish and was discovered in Canada. It is a fossil with more than 505 million years and it is believed that it was one of the fish that inhabited in the Cambrian period .
  • Megalosaurus : it was unearthed in England and was identified as a human giant at the beginning but later after several studies it was determined that it was a dinosaur .
  • Mosasaurus : a marine reptile that was identified as an extinct species that lived during the Cretaceous period .
  • Halszkaraptor : It was basically a duck-like dinosaur that had many of the characteristics that birds have today.
  • Lucy : It is considered the most famous fossil that has been discovered. Its discovery was made in Ethiopia and it is one of the most complete skeletons that have been found of a human ancestor who walked upright . Their brain is the same size as a primate and from there they get the most complete proof of the monkey-man link .

Leave a Comment