''Trigonoceras'' is an extinct genus of prehistoric nautiloids from the nautilid family

Trigonoceratidae The Trigonoceratidae is a family of coiled nautiloid cephalopods that lived during the period from the Early Carboniferous ( Mississippian) to the Early Permian. Diagnosis Trigonoceratidae comprise members of the order Nautilida characterized ...

that lived during the Early

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 ...

in what is now western Europe. ''Trigonoceras'' has a very loosely coiled gyroconic or cyrtoconic shell with a subtriangular cross section, as indicated by fragmentary specimens. The venter on the outer rim or convex side is broad and transversely concave with angular shoulders; the sides which converge on a narrow dorsum are broadly convex. 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 ...

is slightly dorsal of the center and is orthochoanitic.(,B.1964.) A member of the Trigonoceratidae, ''Trigonoceras'' is also a component of the superfamily Trigonocerataceae

References

* ,B.1964. Nautiloidea-Nautilida ''in the''

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...

Part K; Geological Society of America and University of Kansas Press
(Cephalopda)
-Sepkoski's Online Genus Database Prehistoric nautiloid genera {{paleo-Nautiloidea-stub