Two Fossil Ammonites (Jeletzkytes) - South Dakota

This is a 2.7" wide section of rock that contains two Jeletzkytes sp. ammonite fossils, collected from the Fox Hills Formation of South Dakota. The smallest of the two ammonites was removed from the rock it was found in, prepped and then remounted to this rock.

One edge of the rock has been cut flat to facilitate aesthetic presentation of the ammonites without the need for a display stand.

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.

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.
Jeletzkytes sp.
North Central, South Dakota
Fox Hills Formation
Ammonites: .9" & 1.1", Rock: 2.7 x 1.6"
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