When Is It a Fossil

Well-preserved remains of living insect species in the Quaternary, and even lifelike preservation of extinct species in amber millions of years old, forces the question as to when remains are considered fossils. After one million years? After the original remains have been replaced by minerals? For some, a fossil is the remains of a species that has become

2.36. A botfly puparium (Cobboldia) from the stomach of a mammoth found in Siberia. Paleontological Institute Moscow (PIN) Q-TA-1/1; length 19 mm.

There is considerable confusion among nonpaleontologists as to how fossils are dated. Usually, the layers or strata in which the fossils occur are dated, but some fossils can be directly dated using isotope methods, and for yet other kinds of fossils the taxon itself reflects a geological stage or period. The classical geological time scale, with periods, epochs, and ages, codifies major biotic episodes in earth history. When eighteenth- and early nineteenth-century geologists

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