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

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

of North America and Europe, defined by

Alpheus Hyatt Alpheus Hyatt (April 5, 1838 – January 15, 1902) was an American zoologist and palaeontologist. Hyatt served as the founding president of the American Society of Naturalists from 1883 to 1884 and was the founding editor of the journal '' T ...

in 1884. Pseudorthocerids are a kind of orthocertaoid, a taxonomic group within the

Nautiloidea 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 ...

. 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 apices. Surface ornamentation varies but longitudinal lirae are conspicuous from earliest stage. The

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

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 camerae are linked by ...

References

* Sweet, W.C. 1964. Nautiloidea -Orthocerida.

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...

, 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