Eocarcinosoma is a genus of eurypterid, an extinct group of aquatic arthropods. The type and only species of Eocarcinosoma, E. batrachophthalmus, is known from deposits of Late Ordovician age in the United States. The generic name is derived from the related genus Carcinosoma, and the Greek eós meaning 'dawn', referring to the earlier age of the genus compared to other carcinosomatid eurypterids.
Ormoceras is an actinocerid nautiloid genus and type for the family Ormoceratidae, found in North America from the late Chazyan through the early Cincinnatian of the Middle and Upper Ordovician, but which continued through the Devonian worldwide.
Armenoceras is a genus of actinocerid nautiloid cephalopods whose fossils ranged from the late Whiterockian Stage in the early Middle Ordovician, through the remainder of the period and on into the Upper Silurian. It is the type genus of the family Armenoceratidae.
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.
Slender Oncoceratidae are those in the family Oncoceratidae, which have slender, commonly curved, shells. Some like Oocerina are gently curved, almost straight, and with only slight expansion. Others like Dunleithoceras are strongly curved with a more notable rate of expansion. Inclusion in this somewhat arbitrary category is based on illustrations in the Treatise Part K, 1964.
The Brevicoceratidae is a family of oncocerids that contains genera characterized by exogastric gyrocones, brevicones, and torticones. that tend to develop vestigial actinosiphonate deposits and subtriangular transverse sections. The Brevicoceratidae are derived from Oonoceras (Oncoceratidae) and range from the mid-Silurian to the Upper Devonian.
Osbornoceras is a genus of Lower Silurian cyrtoconic nautiloid cephalopods known from Ohio and possibly Manitoba, one of five general currently included in the oncocerid family Karoceratidae.
Geisonoceratidae is an extinct family of orthoceroid cephalopods endemic to what would be Asia, Europe, and North America from the Middle Ordovician to the Middle Devonian living from about 470—380 mya, existing for approximately 90 million years. With the possible addition of an Early Cretaceous orthocerid from the western Caucasus the range of this group increases dramatically to some 350 million years, thus making it one of the longest lived families of the Nautiloidea.
Jovellaniidae was established as a family within the Oncocerida to include genera characterized by longiconic orthocones and cyrtocones with a subtriangular to depressed cross-section in which the ventral (siphuncular) side is typically angular or more acutely rounded than the dorsal (antisiphuncular) side, and in which the siphuncle is generally large, ventral, and with lamellar actinosiphonate deposits
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.
The Naedyceras group comprises three similar and closely related openly coiled, gyroconic, genera within oncocerid family, Brevicoceratidae: Naedyceras, Gonionaedyceras, and Gyronaedyceras.
The Valcouroceratidae is a family within the Oncocerida, nautiloid cephalopods from the middle and upper Ordovician, established by Rousseau Flower in 1945.
Manitoulinoceras is a genus of Late Ordovician oncocerid nautiloid cephalopods, found in North America. The shell is cyrtoconic, exogastric, more strongly curved than in Kindleoceras. The cross-section is somewhat wider than high, with a somewhat flattened upper side, known as the dorsum. Actinosiphonate deposits in the siphuncle are confined to the early part of the phragmocone.
Minganoceras is a genus in the oncocerid family, Valcouroceratidae, named by Foeste, 1938, from the Middle Ordovician of Quebec, found on Mingan Island.
Actinomorpha is a genus of valcouroceratid, order Oncocerida, from the Middle Ordovician of central North America, named by Rousseau Flower, 1943. The shell is breviconic, short and laterally compressed; the venter more narrowly rounded than the dorsum, having the effect of a modest keel in horizontal orientation. The shell is gibbous adorally, such that the body chamber is widest well behind the aperture. The siphuncle is ventral, which could also be indicative of a horizontal orientation in life, with broad, slightly inflated segments and continuous, radial, actinosiphonate, deposits.
Augustoceras is a genus of nautiloid cephalopods included in the order Oncocerida and family Valcouroceratidae. It is known form the Middle and Upper Ordovician of Kentucky and Ohio in the US.
Macrodomoceras is a genus of oncocerids, family Polyelasmoceratidae, from the Middle Devonian of Australia.
Polyelasmoceratidae is a family of oncocerid nautiloids characterized by rapidly expanding endogastrically curved shells, curved such that the ventral side is longitudinally concave. In cross section shells are typically tear-drop in shape to subtriangular. The siphuncle is typically nummuloidal, like a string of beads, with outwardly flared septal necks, and located between the center and the venter. Most contain radially lamellar actinosiphonate deposits.
Eothinoceratidae is a family of Lower Ordovician nautiloid cephalopods included in the Cyrtocerinida. The family was originally established for the genus Eothinoceras.
