2.85" Fossil Ammonite (Rhaeboceras) - Bearpaw Shale, Montana

This 2.85" wide ammonite (Rhaeboceras) fossil is from the Bearpaw Shale of Montana. It offers peeks at the beautiful underlying sutures and brief flashes of iridescence.

Comes with an acrylic display stand.

Ammonites were predatory mollusks that resembled a squid with a shell. These cephalopods had eyes, tentacles, and spiral shells. They are more closely related to a living octopus, though the shells resemble that of a nautilus. True ammonites appeared in the fossil record about 240 million years ago. The last lineages disappeared 65 million years ago at the end of the Cretaceous.

What an ammonite would have looked like while alive.
What an ammonite would have looked like while alive.

These 70 million year old ammonites lived when South Dakota was a shallow inland sea. It was found preserved in a concretion that was split open. It then had to be hand prepared to remove the hard rock surrounding it from the shell, a very time consuming task.
Rhaeboceras halli
Rosebud County, South Dakota
Bearpaw Shale - Baculites reesidei Zone
2.85" wide
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