Cretaceous Fossil Ammonite Cluster - South Dakota

This is a fossil ammonite cluster from the Fox Hills Formation of South Dakota. It's been wonderfully prepared on the hard concretion it was found in. It contains a 1.7" Hoploscaphites nicolletti, a 2.9" Hoploscaphites spedeni and a 1.2" Discoscaphites gulosus. The total height of this cluster is 3.2" In addition to the ammonites, there are a number of fragments and shells still partially concealed in the stone. The ammonites are iridescent and stand out nicely against the dark stone.

There are crack repairs through the Hoploscaphities nicolletii and both the Hoploscaphites spedeni and Discoscaphites gulosus ammonites were removed from the rock, prepped and then remounted to the original portion of the rock they were found in.

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.
Hoploscaphities nicolletii, Hoploscaphites spedeni, Discoscaphites gulosus
South Dakota
Fox Hills Formation
1.7" H. nicolletti, 2.9" H. spedeni, 1.2" D. gulosus, 3.2" tall
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