Ammonoids Ammonoids Boldfaced terms are linked to the Glossary. Ammonoids were squidlike creatures that lived inside an external shell. In fact, ammonoids are relatives of the modern squid, as well as the octopus and chambered Nautilus, all of which belong to the group of animals called cephalopods.
Ammonoid fossils are fairly common in the Cretaceous rocks of western Kansas.
They are also found in Pennsylvanian and Permian outcrops in the eastern part of the state. The two ammonoids shown here are from Pennsylvanian rocks in southeastern Kansas. The lower specimen is Schistoceras missouriense, collected from the Drum Limestone, about 6.5 miles northeast of Independence, Kansas. Ammonoids were important predators in the ancient oceans, eating fish, crabs, and other shellfish. The discovery of fossil ammonoids with bite marks tells us that ammonoids also were preyed upon by larger vertebrates, such as fishes, sharks, and mosasaurs.