Ammonoids were a group of sea creatures that flourished in the Devonian through Cretaceous periods.  The name of these marine cephalopods comes from the "ram's horn" shape of their shells because the Egyptian god Amun or Ammon had a pair of ram's horns.  Despite their resemblance to modern-day Nautiloids, Ammonoids' closest living relatives are probably octopi, squid, and cuttlefish.

Ammonoid shells were divided into chambers by divisions called septa.  The attachment of the septa to the shell exterior created suture patterns which are used to classify Ammonoids.  The "Goniatitic" zigzag pattern of smooth lobes and saddles is characteristic of the earlierGoniatites.  The later Ammonites had a more intricate fern-like suture pattern.