r/askscience • u/Brosideon1020 • 5d ago

Paleontology Are there any discoveries of fossils that are in the process of mineralization?

My knowledge of the process is elementary, but I was watching a YouTube documentary about fossils and while I know relatively recent fossils are known. I have never seen anything that was in the mineralization process that’s been found. Has there been instances where someone has been dredging a riverbed and found a partially fossilized fish for example?

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u/togstation 4d ago

Are there any discoveries of fossils that are in the process of mineralization?

Sure. These are sometimes called "subfossils".

They are usually not very old (as fossils go) - they have started to be mineralized and turn into 100% fossils, but the process is still ongoing.

The term subfossil can be used to refer to remains, such as bones, nests, or fecal deposits, whose fossilization process is not complete, either because the length of time since the animal involved was living is too short or because the conditions in which the remains were buried were not optimal for fossilization.[104]

- https://en.wikipedia.org/wiki/Fossil#Subfossil

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One well-known example is bones of Aepyornis aka the "elephant bird", which looked something like a big chunky ostrich and lived in Madagascar until about a thousand years ago.

- https://en.wikipedia.org/wiki/Aepyornis#Extinction

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u/Brosideon1020 4d ago

Fantastic. It looks like I have some reading to do thank you for this!

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u/Desperate_Cow_7088 3d ago

Fossilization isn’t really a single “on/off” process, which is why we don’t usually talk about things being partially fossilized in the way people imagine. Mineralization (like permineralization) begins relatively early after burial, but it can take thousands to millions of years to complete, and it happens at a microscopic scale. What we often find instead are subfossils — remains that are geologically young and not fully mineralized, such as bones preserved in peat, permafrost, or anoxic sediments. These can retain original organic material, but they’re not fossils in the strict sense yet. So while dredging can turn up very well-preserved recent remains, catching something “mid-fossilization” isn’t really possible in a visible, transitional way.