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What is a fossil?

A fossil is a naturally occurring artifact of ancient life. (A bone from a recently deceased chicken found in your back yard would not be considered a fossil, nor would a footprint in concrete.)

Examples of types of fossils include:

  • entire organisms frozen in glaciers or in permafrost

  • shells and bones

  • casts or molds of hard parts

  • footprints, burrows, root casts

  • plant fossils, including wood replaced by silica precipitated from ground water

  • permineralized feces (coprolites)

Fossils range in size from quite large (e.g., fossil tree trunks and dinosaur bones) to microscopic fossils (microfossils) and pollen.

The most common types of fossils are marine invertebrates (animals with shells) and microfossils. Animals that lived on dry land are much less likely to be preserved as fossils.

References and suggested reading

Callomon, J.H., 2001, Fossils as geological clocks, in Lewis, C.L.E., and Knell, S.J., [editors], The age of the Earth -- from 4004 BC to AD 2002: The Geological Society, London, Special Publication 190, p. 237-252, ISBN 1-86239-093-2.

Clarkson, E., 1998, Invertebrate paleontology and evolution [4th edition]: Oxford, UK, Blackwell Science, 468 p., ISBN 0-632052384.

Cooper, J.D., Miller, R.H., and Patterson, J., 1986, A trip through time -- principles of historical geology: Columbus, Ohio, Merrill Publishing Company, 469 p., ISBN 0-675-20140-3.

Prothero, D.R., 1997, Bringing fossils to life: an introduction to paleobiology: New York, McGraw-Hill, 480 p., ISBN 0-070521972.

Rudwick, M.J.S., 1976, The meaning of fossils -- episodes in the history of paleontology: Chicago, University of Chicago Press, 285 p., ISBN 0-226-73103-0.

Stanley, S.M., 1986, Earth and life through time: New York, W.H. Freeman and Company, 690 p., ISBN 0-7167-1677-1.

The information on this page was written and approved by the faculty of the Geology Department at Baylor University.