''Brevicoceras'' is an extinct nautiloid genus from the order

Oncocerida The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian (early Carboniferous; one possible member is known from the Early Permian), in which the connecting rings are t ...

Flower, R.H & Kummel, B 1950, A Classification of the Nautiloidea, Journal of Paleontology 24(3) Sept 1950 with wide distribution in the Middle

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 ...

in Eastern North America, Russia and Morocco.Kroger, B. 2008. Nautiloids Before and During the Origin of Ammonoids. Special Papers in Palaeontology 79, The Palaentological Association, London. Nautiloids form a broad group of shelled

cephalopods 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, an ...

that were once diverse and numerous but are now represented by only a handful of species in two

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

Taxonomy

Brevicoceras was named by Flower in 1938.Sweet, W. C. 1964. Nautiloidea -Oncocerida.

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, Teichert & Moore (eds) and is the type genus for the

Brevicoceratidae The Brevicoceratidae is a family of oncocerids that contains genera characterized by exogastric (or rarely endogastric) gyrocones, brevicones, and torticones. that tend to develop vestigial actinosiphonate deposits and subtriangular transverse ...

Morphology

''Brevicoceras'' produced short, breviconic, shells in which the ventral side of the phragmocone, or chambered part, is longitudinally convex in profile and the opposite dorsal side concave, resulting in their being exograstric - i.e. upwardly curved. The shell reaches its maximum width near the front of the phragmocone or rear of the living chamber. From there it narrows somewhat toward the transverse and slightly contracted

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...

In section the shell is slightly broader that high. The dorsal side is also somewhat flattened while the ventral or siphuncular side is more narrowly rounded. Septa are shallow and evenly curved; sutures are with broad shallow dorsal and ventral lobes that diverge to the rear and lateral saddles that diverge forward. 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 ...

located close to the ventral margin is slender with short expanded segments that give it a nummuloidal or beaded appearance, and contains irregular blade-like actinosiphonate deposits. The aperture has a pair a ventro-lateral salients, or projections, and a narrow mid ventral hyponomic sinus confirming the siphuncle is ventral.

References

* Sepkoski, J.J. Jr. 2002. A compendium of fossil marine animal genera. D.J. Jablonski & M.L. Foote (eds.). ''Bulletins of American Paleontology'' 363: 1–560
Sepkoski -CEPHALOPODA
{{Taxonbar, from=Q16975295 Oncocerida Paleozoic life of Ontario