Is this a shell fossil?

[fossillissof]

Found these two shells while hiking in the Panoche foothills in CA. Not near the ocean so figured they could be fossils, yeah? They are around two inches (5cm?). 

Edited January 3, 2023 by fossillissof

[Darktooth]

Yes these are oyster shells.

[fossillissof]

9 minutes ago, Darktooth said:

Yes these are oyster shells.

Thanks! This may sound silly, but how can you tell the difference between a regular oyster shell and a fossilized one?

[Darktooth]

Well to be honest I can't say for sure that someone wasn't eating oysters and dumped the remains 100 miles from the nearest Ocean. 

But Fossil Oysters are not uncommon. 

Yours appears to have a weathered look common with fossilized shells.

[fossillissof]

25 minutes ago, Darktooth said:

Well to be honest I can't say for sure that someone wasn't eating oysters and dumped the remains 100 miles from the nearest Ocean. 

But Fossil Oysters are not uncommon. 

Yours appears to have a weathered look common with fossilized shells.

Well, I'll just assume it's a fossil and not someone's leftover food haha thank you for responses, you've been very helpful!

[digit]

The coloration of where the adductor muscle attached seems quite bold and I'm not sure how long this coloration lasts in fossil oysters. @MikeR would have the best perspective on that. This is a type of mollusk that is often carried to remote locations in quantity and slurped with the accompaniment of lemon juice or a cocktail/horseradish sauce and possibly a bottle of bubbly for some celebration. It is not entirely out of the range of possibility that this is the remains of someone's gustatory experience while out enjoying nature.

 

If these were pretty isolated and not found in association with other shelly material or limestone blocks from which they might have eroded then that probably diminishes the fossil theory. If other marine fossil material has been known from the area there is always the chance that these could be much older. Oyster shells are made of calcitic calcium carbonate which is more resistant to erosion than the aragonitic calcium carbonate of most other mollusks.

 

 

Cheers.

 

-Ken

[fossillissof]

16 minutes ago, digit said:

The coloration of where the adductor muscle attached seems quite bold and I'm not sure how long this coloration lasts in fossil oysters. @MikeR would have the best perspective on that. This is a type of mollusk that is often carried to remote locations in quantity and slurped with the accompaniment of lemon juice or a cocktail/horseradish sauce and possibly a bottle of bubbly for some celebration. It is not entirely out of the range of possibility that this is the remains of someone's gustatory experience while out enjoying nature.

 

If these were pretty isolated and not found in association with other shelly material or limestone blocks from which they might have eroded then that probably diminishes the fossil theory. If other marine fossil material has been known from the area there is always the chance that these could be much older. Oyster shells are made of calcitic calcium carbonate which is more resistant to erosion than the aragonitic calcium carbonate of most other mollusks.

 

 

Cheers.

 

-Ken

I know nothing about fossilized oysters, but I too thought it had a very dark color where the muscle attached to the shell. I am really hoping I didn't just grab somebody's discarded food remains haha as far as other shells go, I found these in the same area, along with several others. About twenty miles away there is a sign that says they excavated plesiosaur fossils in the area, so that's a decent indicator that the oysters could still potentially be fossilized, yeah?

[DPS Ammonite]

Can’t tell you if the oyster is old or not. I tend to think that it is newer since the muscle scar is colored. Did you find any fossils in the rocks? The Moreno Formation contains Cretaceous fossils such as those associated with fossil hydrocarbon seeps that formed carbonate mounds with mollusks and tube worms. One of the best spots in California to find dinosaurs and mosasaurs.

 

What formation did they come from?

 

https://www.researchgate.net/figure/Simplified-geologic-map-of-the-southeastern-Panoche-Hills-showing-major-lithologic-units_fig1_225697351

 

https://www.researchgate.net/profile/Daniel-Minisini/publication/225697351_An_ancient_linked_fluid_migration_system_Cold-seep_deposits_and_sandstone_intrusions_in_the_Panoche_Hills_California_USA/links/5a1232eea6fdccc2d79b6b78/An-ancient-linked-fluid-migration-system-Cold-seep-deposits-and-sandstone-intrusions-in-the-Panoche-Hills-California-USA.pdf

[fossillissof]

23 minutes ago, DPS Ammonite said:

Can’t tell you if the oyster is old or not. I tend to think that it is newer since the muscle scar is colored. Did you find any fossils in the rocks? The Moreno Formation contains Cretaceous fossils such as those associated with fossil hydrocarbon seeps that formed carbonate mounds with mollusks and tube worms. One of the best spots in California to find dinosaurs and mosasaurs.

 

What formation did they come from?

 

https://www.researchgate.net/figure/Simplified-geologic-map-of-the-southeastern-Panoche-Hills-showing-major-lithologic-units_fig1_225697351

 

https://www.researchgate.net/profile/Daniel-Minisini/publication/225697351_An_ancient_linked_fluid_migration_system_Cold-seep_deposits_and_sandstone_intrusions_in_the_Panoche_Hills_California_USA/links/5a1232eea6fdccc2d79b6b78/An-ancient-linked-fluid-migration-system-Cold-seep-deposits-and-sandstone-intrusions-in-the-Panoche-Hills-California-USA.pdf

oof, I'm not entirely sure what I am looking at on the geological map, sadly I am very inexperienced. The sign that mentioned the plesiosaur mentioned something about the Moreno Formation, so possibly there. I did not find any fossils in rocks this time, however, my mother did when she came down here. She gave it to me; I'll attach a picture. I believe it's a brachiopod? 

[I_gotta_rock]

I've studied a lot of fossil shells from a lot of different ages. I'm on the fence. Pleistocene shells and Miocene shells can retain their color pretty well, and in fact can be difficult to distinguish if found washed up on a beach with their descendants. The circular gastropod is a modern land snail. At first glance, the other gastropod in the picture looks like Mariacolpus plebia from the east coast, which is Miocene-{Pleistoene and fits the timeline for the adductor scar to possibly be colored. M. plebia is only on the east coast, though. I don't know what turret shell might have been a correlate in California. Fossil hunter left their lunch and the turret shell fell out of the bag? It's not the same age as the plesiosaur deposits. They're too old. This genus wasn't around that early and they wouldn't have retained their color that long if they were.

Edited January 3, 2023 by I_gotta_rock

[MikeR]

The oyster is not a fossil as it has too much protein "sheen" within the shell.  Also if anything it looks like Crassostrea virginica aka the Virginia or East Coast Oyster.

[I_gotta_rock]

It seems we have come to a consensus,. For future reference, the easiest way to rule it out a fossil would be to look at there other shells. Are there any other shells there that you know to be fossils that retain their color.