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What is fossil?

07 Jan 2021

Fossil is the remains, or traces of remains, of ancient organisms in the earth's crust. (Since the past geologic or prehistory time) or that is removed or taken from the crust as evidence of the life in the past.

It could become the rock by the geological process which is physical, biological, and chemical process. It may maintain its original remains without any changing or slightly changing.

The word "Fossil" comes from the Latin word fosiller that means dig and fossilis or fossus means dig up.

Definition:Geology Vocabulary of Royal Institute Dictionary, 2001

The remains, or traces of ancient life which imprint in the rock. Some of them is the print and some is the original remain such as animal footprint, dung, coal, and petrified wood. The phylum or class that can indicate the age of rock is called index fossil.

Definition:Glossary of Geology, (3rd Edition), 1987

n. Any remains, trace, or imprint of a plant or animal that have been preserved in the Earth’s crust since some past or prehistoric time; loosely any evidence of past life.

Adj. Said of any object that existed in the geologic past and of which there is still evidence.

Cf. subfossil

Fossilization: n. All processes involving a burial of plant or animal in sediment and the eventual preservation of all, part, or a trance of it.


n. All processes involving a burial of plant or animal in sediment and the eventual preservation of all, part, or a trance of it.

Legal fossil
Definition:Fossil Protection Act, B.E. 2551

Fossil means the remains, or traces of the ancient living organism in the earth's crust that removed or taken from the earth's crust. There are not including the legal antiques, artifact, and national museum.

Fossil site means the place where discovered or had the fossil.

Definition:Ancient Monuments, Antiques & National Museums Act, 1961

Antiquities mean the ancient properties whatever it is the invention or anything happening naturally including the part of ancient monuments or human remains or animal remains by age or by invention or the history of such ancient properties is useful in art History or archeology.

  • The study of fossil is the part of Paleontology and Paleobiology.
  • Paleontology: The study of the living organism in the past which is obtained by remains or trace of ancient animal and plant including evolution of life including the relationship between the life in the past and present, the past life and environment, and the comparison of relationship in order to define the sequence of events in the earth's history.
  • Paleobiology: It is the part of the paleontology which is the study of fossil and focus on the life instead of the relationship comparison of the life in the past.
Dinosaur Fossil

The most well-known fossil is dinosaur bone, dinosaur footprint, shell, coral , fish , leaf, and insect which its shape and structure is as similar as existing in present.

Sometime the fossil of extinct animal or plant had been found. However, its shape is similar to the present species which has the evaluation from its parent. So it can be indicated the species of such the fossil.

For the dinosaur fossil, even the dinosaur is already extinct. Its story is still mystery that cannot be found in present. Moreover, its huge size is also interested and memorable.

The Formation of Fossils

The living organisms die in the suitable environmental condition and are buried in mud and silt. Over time sediment builds over the top and turns into stone.

The process of fossil formation is called Fossilization.


The fossil is formed by fossilization process. There are generally classified into 4 types as follow:

  • Unaltered soft parts
  • Unaltered hard parts
  • Altered hard parts
  • Trace fossils or Ichnofossils or Lebenspurren

1.Fossil is usually from the remains of living organism which die and rapidly buried in sediment.

2.Soft parts which is skin and muscle quickly decompose and the hard parts which is bone is covered by the layer of sediment in order to maintain its condition.

3.1)Over time sediment builds over the top and hardens into rock. Minerals seep into the tiny space of the bone and produce rocks in the shape of the animal or plant. In this case, the shape and structure is similar to the real bone.

3.2)The replacement of mineral occurs in case of the bones completely decay. The void left behind may then fill with minerals making a stone replica of the organism. In this case, its shape is similar to the bone but no structure inside.

4.The movement of the Earth's crust causes that the rock of the fossils remain lift up to the surface of the Earth. The rock is uncovered through erosion or excavation.

Why does the discovered fossils not usually in the completed condition?

Generally, the living organisms consist of the tissue and the hard parts such as bone, shell, scales, nail, and thorn. Once the living organism die, the tissue is decomposed easily under the earth's atmosphere condition while the hard part is more resistant. So the soft parts are usually decomposed before covering by sediment. That's why the soft part of fossil is rarely discovered. In some case, the whole mammoth was found in Siberia because the cold weather could maintain its condition preventing the decomposing. The common fossil is the hard parts such as tortoiseshell, shells, ancient fish scales, ancient armor plate, teeth, and leaf. It mostly found as an imprint in the rock.

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