The Ellesmerocerida is an order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician.
The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian, in which the connecting rings are thin and siphuncle segments are variably expanded. At present the order consists of some 16 families, a few of which, such as the Oncoceratidae, Brevicoceratidae, and Acleistoceratidae contain a fair number of genera each while others like the Trimeroceratidae and Archiacoceratidae are represented by only two or three.
Tetragonoceras is an extinct prehistoric nautiloid genus from the nautilid family Tetragonoceratidae that lived during the Middle Devonian, found in Canada.
Homaloceras is an extinct nautiloid cephalopod from the Middle Devonian with a strongly curved shell, included in the nautilid family Centroceratidae.
Endolobus is an extinct genus from the nautiloid order, Nautilida. Nautiloids are a subclass of shelled cephalopods that were once diverse and numerous but are now represented by only a handful of species, including Nautilus. Endolubus is included in the family Koninckioceratidae which is part of the superfamily Tainoceratoidea.
Brevicoceras is an extinct nautiloid genus from the order Oncocerida with wide distribution in the Middle Devonian in Eastern North America, Russia and Morocco. Nautiloids form a broad group of shelled cephalopods that were once diverse and numerous but are now represented by only a handful of species in two genera.
Neocycloceras is an extinct genus of nautiloid included in the Pseudorthocerida that lived during the Late Devonian and Mississippian. Neoclycloceras is characterized by a slender, generally circular shell with slightly oblique, sinuous surficial annulations. Its sutures have dorsal and ventral saddles and lateral lobes and become more oblique with age. Saddles point forward, lobes to the rear. Dorsal saddles are broad and low but the ventral ones are high and conspicuous. The siphuncle is located between the center and venter and is nummuloidal, composed of rounded expanded segments, the inside of which contains a continuous laminar lining that is thickest in the middle of the segments and thinnest at the septal necks. Neocycloceras has been found in Pennsylvania in North America and in Morocco in north Africa.
Zittelloceras is an extinct genus of nautiloids from the order Oncocerida which are among a large group of once diverse and numerous shelled cephalopods, now represented by only a handful of species.
Tetrapleuroceras is an extinct prehistoric nautiloid from the Lower Permian of the Urals in Russia. Nautilids are a type of nautiloid, a subclass of shelled cephalopods that were once diverse and numerous but now only represented by Nautilus and Allonautilus
Valhallites is an extinct genus in the nautiloid order Nautilida which includes the living Nautilus found in the tropical western Pacifiic. Valhalites belongs to the Koninckioceratidae, a family in the Tainoceratoidea, a nautilid superfamily.
Tylonautilus is an extinct genus in the nautiloid order Nautilida from the Lower Carboniferous of Europe and Permian of Japan.
Streptoceras is a genus in the extinct oncocerid family Acleistoceratidae that plied the shallow sea floor from the Middle Silurian to the Middle Devonian. Streptoceras is characterized by a shell that is large but short in proportion (breviconic) with the ventral profile convex and dorsal profile concave in the posterior part, convex over the body chamber, then concave toward the front, like Amphycertoceras, but with a triangular shaped aperture. Streptoceras is found in the Middle Silurian of North America, in Ontario.
Shuranoceras is a genus in the extinct oncocerid family Karoceratidae that plied the shallow sea floor from the Early Silurian to the Early Devonian. Shuranoceras is characterized by a smooth, compressed, slowly enlarging orthoconic shell with a ventral submarginal siphuncle composed of complex segments. Shuranoceras was found in middle Silurian strata in Ferghana, central Asia.
Stearoceras is an extinct genus of prehistoric nautiloids from the Lower Pennsylvanian - Lower Permian with a fair worldwide distribution.(Kümmel 1964)
Acleistoceras is a genus of the oncocerid, nautiloid family Acleistoceratidae that lived in the shallow seas that covered much of North America during the Devonian; living from 409—383.7 mya, existing for approximately 25.3 million years.
Basslerocerida is an order of nautiloid cephalopods from the Ordovician comprising exogastric longiconic cyrtocones, that is no longer in common use.
The Trigonoceratoidea are a superfamily within the Nautilida that ranged from the Devonian to the Triassic, thought to have contained the source for the Nautilaceae in which Nautilus is found.
The Graciloceratidae is a family of nautiloid cephalopods from the Middle and Upper Ordovician belonging to the Oncocerida, characterized by exogastric cyrtocones that expand slightly or moderately and have thin walled, orthochoanitic marginal or subventral, tubular siphuncles.
Oncoceratidae is a family of nauatiloid cephalopods in the order Oncocerida established by Hyatt, 1884, that range from the Middle Ordovician to the Upper Silurian.
The Tripteroceratidae is a family of depressed, straight to slightly curved nautiloid cephalopods from the middle and upper Ordovician with generally flattened venters and empty siphuncles with straight to inflated segments included in the Oncocerida.
