Fossils – A Definition

One question that Everything Dinosaur team members get asked when they visit schools is what are fossils?  This seemingly innocuous question is actually quite difficult to answer when the different types of fossil are considered.  Essentially if we were to say that a fossil is the preserved remains of a once-living organism that has been buried in sediment that has over time become rock, this would not be entirely correct.  This particular definition fails to encompass the many and varied different types of fossil that can be found.

A more fundamental definition is required, for example, it would be true to say that a fossil is simply any evidence of ancient organisms, naturally preserved within the materials that make up the Earth.  Usually, such evidence is found within sedimentary rock, the muds, silts and sands that are deposited in layers and over time form rock, but not all fossils are formed in this way small creatures, fungi and plant material can be preserved in tree resin that hardens into amber, Pleistocene animals and plants can be preserved frozen; such as Mammoths in the Arctic wastes of the Siberian Tundra.  Occasionally, organisms may be trapped in fine volcanic ash and preserved in amazing detail and at Starunia in Poland, a complete rhinoceros was discovered pickled in a mixture of brine and tar.  This specimen was over 100,000 years old, but it was so well preserved that its stomach contents could be studied.

The word “fossil” is derived from the Latin word “fossa” meaning “dug up”.  In the 17th Century academics thought fossils consisted of both organic and inorganic matter, but by 1800 most agreed that fossils were purely of organic origin.  However, how fossils came to exist was still hotly debated (indeed, the debate continues today).

Broadly there are three types of fossil; body, trace and chemical fossils the table below provides a brief description and some examples.

Different Types of Fossil

Table Credit: Everything Dinosaur

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