If paleontology is the investigation of the history of life's development, then fossils are the road markers by which they plot their course. Fossils are defined as the remains or traces of plants and animals which before the beginning of the present geological era found their way into the earth and were preserved there. The fossilization of the remains was not common and could take place only under very specific conditions. Ordinarily, the normal process of decay would leave only the hard parts of the living thing, i.e., bones, teeth, and shell. In time, even these gradually disappear as nature and the process of disintegration continue its work.
Fossilization requires a quick burial of the living organism before the processes of decay begin.
Once buried, the organism becomes completely mineralized or petrified . Carbonization , another process of preservation, is most common with plant matter and takes place solely under water without the presence of air. Other sources of fossilized material include, bugs and other arthropods that have been found encased in amber, skeletal remains from California La Brea tar pits, and whole specimens found frozen in tundra. You might be amazed at the number of things fossils can tell us about the geological, geographical , zoological, and botanical history of the Earth. The location where fossils are found and the depth at which they are found have been used to theorize what plants and animals co-existed across time.