Two Species Of Hoploscaphites Ammonites Back To Back - South Dakota
This is a beautiful display piece from the Fox Hills Formation of South Dakota. It features two, associated Hoploscaphities ammonites of different species in the same concretion. There is a 2.1" Hoploscaphities nebrascensis back to back with a 1.95" wide Hoploscaphites comprimus. Both fossils have been nicely prepared from the hard concretion and the base of the rock has been cut flat so it stands up nicely 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. Ammonites appeared in the fossil record about 240 million years. The last lineages disappeared 65 million years ago at the end of the Cretaceous.