What is "stearoceras"

Stearoceras is an extinct prehistoric nautiloid genus from the Lower Pennsylvanian (Upper Carboniferous) - Lower Permian with a fair worldwide distribution.(Kümmel 1964)

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.(ibid)

Nautiloids are a subclass of shelled cephalopods that were once diverse and numerous but are now represented by only a handful of species.