''Spyroceras'' is a genus of pseudorthocerids from the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

of North America and Europe, defined by Hyatt in 1884. Pseudorthocerids are a kind of orthocertaoid, a taxonomic group within the

Nautiloidea 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. ...

. Specifically ''Spyroceras'' belongs to the pseudorthocerid family, Spyroceratidae. ''Spyroceras'' had annulated orthocones with straight transverse sutures, transverse or slightly oblique surface annulations, and faintly cyrtoconic apeces. Surface ornamentation varies but longitudinal lirae are conspicuous from earliest stage. The

siphuncle The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and ...

was central or slightly offset ventrally, and composed of expanded segments typical of the Pseudorthocerida. Cameral and siphonal deposits developed later than in most pseudorthocerids and are thus confined to the apical portion of the

phragmocone The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae. In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a ...

References

* Sweet, W.C. 1964. Nautiloidea -Orthocerida. Treatise on Invertebrate Paleontology, Part K. Geological Soc. of America and Univ of Kansas press.
''Spyroceras'' Paleobio db

Sepkoski List - Cephalopoda
Prehistoric nautiloid genera Paleozoic life of Ontario Paleozoic life of Manitoba Paleozoic life of the Northwest Territories Paleozoic life of Nunavut Paleozoic life of Quebec {{paleo-Nautiloidea-stub