''Cycloceras'' is an extinct

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 ...

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

genus from the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

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 is an order of extinct Orthoceratoid cephalopods also known as the Michelinocerida that lived from the Early Ordovician () possibly to the Late Triassic (). A fossil found in the Caucasus suggests they may even have survived until ...

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 an unusually long straight shell of a nautiloid cephalopod.; During the 18th and 19th centuries, all shells of this type were named ''Orthoceras'', creating a wastebasket taxon, but it is now known that many groups of nautiloids d ...

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