Subfossil (as opposed to fossil) is a term applied to the remains of a once-living organism in cases where the remains are very old indeed, but are not considered to be fully fossil for one of two possible reasons. One possible reason is a simple one: not enough time has elapsed since the organism died. Another possible reason is that the fossilization process is not complete, because the conditions in which the remains were deposited were not optimal for fossilization.
In the first case, for example, with remains such as molluscan seashells, which frequently do not change their chemical composition over geological time, and may occasionally retain even such features as the original color markings for millions of years, the label "subfossil" is applied to shells that are understood to be thousands of years old, but are of Holocene age, and therefore are not old enough to be from the Pleistocene epoch.
In the second case, unfossilized or partially fossilized remains can include bones, exoskeletons, nests, skin imprints, or fecal deposits. Subfossils of vertebrates are often found in caves or other shelters, where the remains have been preserved for thousands of years. The main importance of these vertebrate subfossil (versus fully fossilized) remains is that they contain organic material, which can be used for radiocarbon dating or extraction and sequencing of DNA, protein, or other biomolecules. Additionally, isotope ratios can provide information about the ecological conditions under which extinct animals lived. Subfossils are useful for studying the evolutionary history of an environment and can be important to studies in paleoclimatology.
Subfossils are also often found in depositionary environments, such as lake sediments, oceanic sediments, and soils. Once deposited, physical and chemical weathering may alter the state of preservation, and small subfossils can also be ingested by living organisms.
- "Subfossils Collections". South Australian Museum. Retrieved August 2012.
- Peterson, Joseph E.; Lenczewski, Melissa E.; Scherer, Reed P. (October 2010). "Influence of Microbial Biofilms on the Preservation of Primary Soft Tissue in Fossil and Extant Archosaurs". In Stepanova, Anna. PLoS ONE 5 (10): 13A. doi:10.1371/journal.pone.0013334.
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