2.6" Wide, Iridescent Ammonite (Hoploscaphites) - South Dakota

Wide, Iridescent Ammonite (Hoploscaphites) - South Dakota #38968

This is a rare, red iridescent, Hoploscaphites spedini from the Fox Hills Formation of South Dakota. It's 2.65" wide and preserved in a hard concretion which was split open. These 70 million year old ammonites lived when South Dakota was a shallow inland sea.

Ammonites were predatory cephalopod mollusks that resembled squids with spiral shells. They are more closely related to living octopuses, though their shells resemble that of nautilus species. True ammonites appeared in the fossil record about 240 million years ago during the Triassic Period. The last lineages disappeared 65 million years ago at the end of the Cretaceous.

What an ammonite would have looked like while alive.

More about ammonites