''Codoceras'' is a genus of

nautiloid Nautiloids are a group of marine cephalopods ( Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded species ...

s belonging to the

Polyelasmoceratidae Polyelasmoceratidae is a family of oncocerid nautiloids characterized by rapidly expanding endogastrically curved shells, curved such that the ventral side is longitudinally concave. In cross section shells are typically tear-drop in shape to su ...

, an Oncocerida family. ''Codoceras'', known from the Silurian of Europe, has a compressed, rapidly enlarging shell, curved endogastrically such that the presumed ventral side is concave and the opposite dorsal side is convex. The siphuncle is displaced from the center slightly toward the venter. Early segments are cylindrical. Later ones are nummuloidal and broader. The type species is ''Cyrtoceras indominum'' Barrande 1866. ''

Danaoceras ''Danaoceras'' is a nautiloid cephalopod from the middle Silurian of central Europe included in the oncoceroid family Polyelasmoceratidae. Similar specimens from the middle Devonian of North America may belong. ''Danaoceras'' has a laterally co ...

'' is closely related and its most likely ancestor.

References

* Walter C. Sweet, 1964. Nautiloidea - Oncocerida; Treatise on Invertebrate Paleontology, Part K. Geological Society of America and University of Kansas Press. Prehistoric nautiloid genera Oncocerida {{paleo-nautiloidea-stub