This Specimen has been sold.
1.4" Iridescent, Fossil Ammonite (Discoscaphites) - South Dakota
This is a 1.4" ammonite (Discoscaphites conradi) from the Fox Hills Formation of South Dakota. The iridescence of the outer shell creates a colorful display. This specimen has been well prepared and remains attached to the rock in which it was found. The rock contains a variety of other small marine bivalves and ammonite pieces. There is a repaired crack through the ammonite.
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.