<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> A fossil (from Classical Latin fossilis; literally, "obtained by digging") is any preserved remains, impression, or trace of any once - living thing from a past geological age . Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood, oil, coal, and DNA remnants . The totality of fossils is known as the fossil record . </P> <P> Paleontology is the study of fossils: their age, method of formation, and evolutionary significance . Specimens are usually considered to be fossils if they are over 10,000 years old . The oldest fossils are from around 3.48 billion years old to 4.1 billion years old . The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils . The development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the absolute ages of rocks and the fossils they host . </P>

Different types of fossils and how they are formed