''Cycloceras'' is an extinct

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

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

genus from the

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

of Western Europe, (Ireland and Scotland) of unknown affinity with the Orthocerida.

Taxonomy

''Cycloceras'' was named by McCoy (1844 and assigned to the Michelinoceratida by Flower (1962)and to the

Orthocerida Orthocerida, from Ancient Greek ὀρθός (''orthós''), meaning "straight", and κέρας (''kéras''), meaning "horn", also known as the Michelinocerida, is an order of extinct Orthoceratoidea, orthoceratoid cephalopods that lived from the ...

by Sweet in Teichert et al. (1964);PaleoBiology Database:''Cycloceras'',basic info
/ref> ''Cycloceras'' is possibly a member of the Cycloceratidae and may be synonymous with ''Perigrammoceras''.

Morphology

The type species of ''Cycloceras'', ''C. annularis'', is based in an internal mold of a body chamber on which the position of the siphuncle is indiscernible (Sweet 1964,) Species referred to Cycloceras are annulated, subcylindrical orthocones with no longitudinal ornamentation . Fig 186, p K258 Teichert ''et al.'' (1964) shows ''Cycloceras'' as narrow, gently expanding, annulated

orthocone An orthocone is the long, cone-shaped Exoskeleton, shell belonging to several species of ancient nautiloid cephalopod—the prehistoric ancestors of today's marine cephalopod Mollusca, mollusks, including the cuttlefishes, nautiluses, octopuses an ...

with a narrow subcentral siphuncle. Annuli (circular transverse bands or costae) are thick and close spaced, giving a corrugated appearance.

References

Prehistoric nautiloid genera Carboniferous cephalopods Prehistoric animals of Europe Paleozoic life of Ontario Paleozoic life of Nunavut Orthocerida Fossil taxa described in 1844 Taxa named by Frederick McCoy {{Cephalopod-stub