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Themes > Science > Paleontology / Paleozoology > Fossils And Fossilisation > General Discussion of Fossils > Factors of Preservation |
Some species are represented by the remains of millions of individuals, while the extistence of another species may have been recorded by only a few, or even a single individual. Still others have only left their tracks behind, and some vanished without a trace. What is it that makes some species such good candidates for preservation while there is no record of others? Preservation of fossils depends on a number of factors. Some are obvious. It stands to reason that a common species with lots of individuals and that is geographically widespread over lots of environments, and exists for long geologic times will be more easily preserved than a rare species that lives in a very restricted environment. If an organism has hard parts, it will stand a better chance for preservation. Bones and teeth, shells and wood preserve more easily than the body of a jellyfish. It also helps to bury an organism as rapidly as possible, preferably in fine-grained sediment. This keeps carrion feeders, bacteria and other decomposers from destroying the remains and also protects them from the ravages of weather. This can happen in floods, vulcanic ash falls, dust storms, in burial in permafrost, sinkholes, bogs or tarpits, etc. One of the richest vertebrate deposits ever to be found was excavated from the tar pits of Rancho La Brea in Los Angeles, CA. Fossilized human brain remains have been found in springs in Florida. Of all the environments that have preserved remains however, marine sediments remain the richest source of fossils. |
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