Fossil Ammonite And Whelk Cluster - South Dakota

This is an ammonite (Hoploscaphities) whelk (Buccinidae) cluster from the Fox Hills Formation of South Dakota. It's been wonderfully prepared on the hard concretion it was found in. It contains two central ammonites, the largest being 2.1" and a 2.0" whelk (marine snail). The total height of this cluster is 3.3" In addition to the ammonites and whelk, there are a number of fragments still partially concealed in the stone. The largest ammonite has been reattached to the rock. The ammonites are iridescent and stand out nicely against the dark stone.

About Ammonites

Ammonites were ancient marine cephalopods, similar to today's squids and octopuses, but with a defining feature: their distinctive, tightly coiled spiral shells. These shells, resembling those of modern nautiluses, served as both a protective home and a buoyancy aid, allowing ammonites to navigate the prehistoric seas with ease. First emerging around 240 million years ago in the Triassic Period, ammonites thrived for over 175 million years, adapting through numerous forms and sizes. As predatory creatures, they likely fed on smaller marine organisms, using their tentacles to capture prey. However, their long reign came to an end 65 million years ago at the close of the Cretaceous, coinciding with the mass extinction event that also eliminated the dinosaurs.

What an ammonite would have looked like while alive.

More about ammonites