Stearoceras

Stearoceras is an extinct genus of prehistoric nautiloids from the Lower Pennsylvanian - Lower Permian with a fair worldwide distribution.
Stearoceras is recognized by its involute shell with a depressed subtrapizoidal whorl section and slight ventral and lateral lobes. In contrast Stenoporceras is subdiscoidal and has a suture with broad lateral lobes and a deep ventral saddle as found in syringonautilids.
Nautiloids are a subclass of shelled cephalopods that were once diverse and numerous but are now represented by only a handful of species.