2.7" Fossil Ammonite (Hoploscaphites) - South Dakota

This is a 2.7" ammonite (Placenticeras) from the Fox Hills Formation of South Dakota. It has been wonderfully prepared on the hard concretion it was found in. The ammonite is iridescent and stands out nicely against the dark rock. In addition to the ammonite, shell fragments of other ammonites and gastropods are visible imbedded in the rock.

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. Ammonites appeared in the fossil record about 240 million years ago and they barely survived several major extinction events. The last lineages disappeared 65 million years ago at the end of the Cretaceous.

Hoploscaphites nicolletti
South Dakota
Fox Hills Formation
2.7", 4.4" total height
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