There are over 200 published occurrences of anomalously occurring fossils,
or fossils that show up in strata of ages much different ages than
expected.
Few if any of the "anomalous" fossils are truly anomalous. It is
fairly common for fossils to erode out of an old formation and be
redeposited in a younger formation. (It is usually easy to recognize
such reworked fossils by the extra wear they show.) Pollen, spores,
and other very small fossils can also be blown or washed into tiny
cracks to appear in older formations. The
few anomalies that
remain might be explained by genuine range extensions (see below),
misidentification of the fossil, or uncertain attribution
of where the fossil came from.
For most species, the fossil record is quite spotty. The earliest
known fossil of a species is likely to be quite a bit later than the
earliest appearance of the species; likewise, the latest known fossil
is earlier than the species' extinction. There are plenty of
opportunities for the discovery of new fossils to extend the known
range of a species. It is inappropriate to refer to such new
discoveries as anomalies.
Even 200 anomalies is an insignificant amount compared with the
estimated 250 million fossils that have been catalogued and the much
larger number that have been discovered.
