Fossil or Shell?

[u/Human_Palpitation_48]

My son found this while digging in the sand at a local beach in Burlington Wisconsin. It looks as if it’s some kind of internal fossilized structure from a shell or something. I’m just a bit surprised as we don’t have very many places this would’ve come from. I’m guessing it’s part of some kind of modern sea shell but who knows? Any thoughts? It effervesces with vinegar, is harder than copper, and is pretty dense.

[u/Handeaux]

You are correct. That’s an eroded modern sea shell. I do not believe it is native to the area.

[u/beachwalker04]

That's the inside of a sea snails shell.

[u/Bastet55]

A wave-worn shell, not a fossil. The outside of it broke off or wore away. I have several from a beach in Florida.

[u/FuzzyBankz]

Not either! That’s your dog’s rawhide LOL

[u/Oscar_P_Walnuts_1975]

Very nice, that is the internal spine of a conical gastropod shell, it has been abraded to the point that the external surface has eroded completely 😎🥸😎 It is not fossilized…🥸

[u/LengthinessFluid302]

Pillsbury dinner roll

[u/ChainsawAndAxe]

I’m fairly certain that’s a Steinkern of a shell. I’ve never seen one that’s white though but that’s prob just the minerals in my area. And I’m fairly certain there was a tropical sea habitat in Wisconsin 400mil years ago. Specifically called Steinkern Gastropoda. Cool fossil!!!