Belongs within: Nautilaceae. Nautilus is a genus of smooth-shelled cephalopods known from the Oligocene to the present day (Kummel 1964). Characters (from Kummel 1964): Smooth, nautiliconic, involute to occluded; suture consisting of broad rounded ventral saddle, broad lateral lobe, small saddle in vicinity of umbilical shoulder, shallow lobe on umbilical wall, small saddle near umbilical… Continue reading Nautilus


Belongs within: Oncocerida. The Nothoceratidae are a group of cephalopods known from the Silurian and Devonian. Nothoceratid shells varied from short and curved to coiled, with the mature aperture being variously constricted. Characters (from Sweet 1964): Depressed (or primitively compressed), exogastric or endogastric brevicones, nautilicones, and torticones with contracted or visored apertures and ventral, generally… Continue reading Nothoceratidae


Belongs within: Nautilosiphonata.Contains: Rutoceratidae, Trimeroceratidae, Rizoceratidae, Valcouroceratidae, Jovellaniidae, Nothoceratidae, Polyelasmoceratidae, Oonoceratidae, Diestoceratidae, Hemiphragmoceratidae, Oncoceratidae, Acleistoceratidae, Poterioceratidae. The Oncoceratida were a highly varied group of cephalopods, mostly breviconic but also including other forms including gyroconic and torticonic species. As recognised by Sweet (1964), the oncocerids lived from the Middle Ordovician to the Lower Carboniferous; however, phylogenetically… Continue reading Oncoceratida


Belongs within: Mollusca.Contains: ‘Acaroceras’, Protocycloceras, Ellesmeroceratidae, Piloceratidae, Manchuroceratidae, Coreanoceratidae, Najaceratidae, Bathmoceratidae, Oncoceratida, Nautilida, Tarphyceratida, Ascoceratidae, Naedyceratidae, Brevicoceratidae, Westonoceratidae, Cyrtogomphoceratidae, Mandaloceratidae. The Middle Ordovician to Middle Devonian Discosorida were an order of mostly breviconic or cyrtoconic cephalopods. The major distinguishing feature of the group was the development of thick, layered connecting rings around the siphuncle that… Continue reading Nautilosiphonata


Belongs within: Nautilosiphonata. The Middle Ordovician to Lower Devonian cyrtogomphoceratid lineage of discosorid cephalopods included the paraphyletic Cyrtogomphoceratidae and the later Phragmoceratidae. The Phragmoceratidae had the shell aperture strongly constricted by encroaching lappets. Characters (from Teichert 1964): Conchs dominantly medium-sized to large, compressed endogastric cyrtocones; aperture strongly contracted in Phragmoceratidae; siphuncle close to ventral side.… Continue reading Cyrtogomphoceratidae


Belongs within: Nautilosiphonata. The Middle Ordovician to Middle Devonian westonoceratid lineage included the paraphyletic Westonoceratidae and its descendant families Lowoceratidae and Discosoridae. Characters (from Teichert 1964): Conchs mostly compressed exogastric cyrtocones (endogastric in Discosoridae, slender in Lowoceratidae); siphuncles moderate-sized; apertures constricted or open. Connecting rings thin to moderately thick; bullettes inflated in early forms, less… Continue reading Westonoceratidae


Belongs within: Nautilosiphonata. The Lower Ordovician Ellesmeroceratidae were a family of straight-shelled or cyrtoconic cephalopods, many of them relatively small. Characters (from Furnish & Glenister 1964): Orthoconic longicones and compressed endogastric breviconic cyrtocones with marginal siphuncle, ellipochoanitic septal necks and thick, layered connecting rings; often with irregular diaphragms. <==Ellesmeroceratidae [Ellesmereoceratidae, Stemtonoceratidae, Robsonoceratidae] |–Paradakeoceras minor Flower… Continue reading Ellesmeroceratidae


Belongs within: Nautilosiphonata. The Piloceratidae were a family of Lower Ordovician breviconic endocerid cephalopods. They had a large endocone-packed siphuncle occupying a large part of the shell. Characters (from Teichert 1964): Breviconic, more or less strongly curved, rapidly expanding conches with compressed section; body chamber may have slightly contracted aperture. Siphuncle rapidly expanding, large; septal… Continue reading Piloceratidae


Belongs within: Nautilosiphonata. The Lower Ordovician to Upper Devonian Tarphycerida were the earliest lineage of coiled cephalopods. In a number of forms, the later whorls become separated from the older part of the shell; in the family Lituitidae the later part of the shell becomes straight and much larger than the coiled part. The siphuncle… Continue reading Tarphyceratida


Belongs within: Oncoceratida. The Acleistoceratidae were a Middle Silurian to Middle Devonian family of oncocerid cephalopods characterised by a broad siphuncle. Many species had a constricted triangular aperture. Characters (from Sweet 1964): Depressed (rarely compressed, at least in early stages) exogastric brevicones and cyrtocones; siphuncle broadly expanded, actinosiphonate in some Devonian species. <==Acleistoceratidae |–EocyrtocerasK93 |–Austinoceras… Continue reading Acleistoceratidae