| Osbornoceras Temporal range: | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | Nautiloidea |
| Order: | † Oncocerida |
| Family: | † Karoceratidae |
| Genus: | † Osbornoceras Foeste, 1936 |
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.
Osbornoceras grew to be somewhat large and is characterized by a narrow, compressed, strongly curved, exograstric shell. The venter, on the outside curvature, is narrowly rounded while the dorsum, on the opposite inside curvature, is more broadly rounded. The body chamber narrows toward the aperture, which has a deep hypomomic sinus.
The siphuncle of Osbornoceras is ventral but not in contact with the ventral wall of the shell. Segments are empty and expanded ventrally but are virtually straight dorsally. Connecting rings are thin, septal necks cyrtochoanitic (outwardly flared).
Karoceras , from Europe and Russia, which followed in the Middle Silurian, is similar in overall form but is actinosiphonate. Its siphuncle in contrast contains blade-like deposits which project radially inward. Also similar is the closely related Lower Devonian Ankyloceras and earlier Middle and/or Upper Ordovician oncoceratids such as Diagenoceras and Richardsonoceras .
Osbornoceras and similar oncocerids were probably benthic predators that lived on the seafloor oriented in life as to face forward with the body chamber parallel to the seafloor and curved phragmocone arched upward. Whether they were pursuit of ambush predators is unknown. Also unknown is the number of arms. Was it the primitive 8 or 10 or the derived 90 plus found in recent Nautilidae.
The Bactritida are a small order of more or less straight-shelled (orthoconic) cephalopods that first appeared during the Emsian stage of the Devonian period with questionable origins in Pragian stage before 409 million years ago, and persisted until Carnian pluvial event in the upper middle Carnian stage of the Triassic period. They are considered ancestors of the ammonoids, as well as of the coleoids.
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.
Ankyloceras is a genus of Early Devonian cephalopods included in the oncocerid family Karoceratidae. The type species, Ankyloceras nesnayamiense named by Zhuravleva, 1974, comes from Nova Zemlya in Russia. Other species have been found in Japan, Morocco, and Russia.
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.
Bactroceras is a genus of orthoceratoid cephalopods that lived during the early Middle Ordovician, from about 472—464 mya, existing for approximately 8 million years.
Sactoceras is an extinct nautiloid cephalopod that lived during the Ordovician and Silurian in what would become North America, Europe, and Asia.
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 Phragmoceratidae is a family of extinct nautiloid cephalopods from the Order Discosorida that lived during the latter part of the Silurian.
Mandaloceratidae is a family in the nautiloid cephalopod order Discosorida, from the Middle and Upper(?) Silurian characterized by short, essentially straight shells referred to as breviconic, typically with a faintly exogastric shape produced by the profile of the body chamber.
The Naedyceras group comprises three similar and closely related openly coiled, gyroconic, genera within oncocerid family, Brevicoceratidae: Naedyceras, Gonionaedyceras, and Gyronaedyceras.
Blakeoceras is a nautiloid cephalopod from the Oncocerida family Nothoceratidae with a curved shell that lived in shallow seas from the Silurian to the Middle Devonian in what has become Europe.
Galtoceras is a cyrtoconic nautiloid from the Middle Silurian of North America, named by Foerste in 1934.
Gonatocyrtoceras is a genus of oncocerid nautiloids belonging to the family Acleistoceratidae, that lived during the Middle Devonian. Gonatocyrtoceras is characterized by strongly curved, depressed, breviconic shells. Curvature is exogastric, meaning the lower, or ventral, side is convex in longitudinal profile. The aperture is without a hyponomic sinus. The siphuncle is small and subventral.
Cyrtogomphoceras is a genus of nautiloid cephalopods, recognized by its large breviconic shell with a notable endogastric curvature. The shell is fusiform in profile, reaching maximum width at or near the base of body chamber, which narrows toward the aperture. The siphuncle is large and slightly removed from the ventral side, that with the concave longitudinal profile. Siphuncle segments are short, as are chambers; septal necks recurved, connecting rings thick, bullettes at the apical end of the rings swollen. Cameral deposits are lacking.
Kentlandoceras is a genus of middle Ordovician Oncocerids. Its shell is curved exogastrically, such that the ventral margin is longitudinally convex, but less so than in Loganoceras, and with a submarginal ventral siphuncle instead. The siphuncle in Loganoceras is subcentral. The related Romingoceras is more curved, also with a ventral siphuncle.
Karoceras is a genus of oncocerid nautiloids that lived during the Silurian and possibly Early Devonian, type genus for the Karoceratidae. The shell is a compressed, exogastric cyrtocone, section sub ovoid. The siphuncle is ventral, near the outer, externally convex curvature. Septal necks flair outwardly, segments are inflated ventrally and are straight dorsally, a character of the family.
Karoceratidae is a family of nautiloids within the order Oncocerida, characterized by straight or curved, laterally narrow, shells and slender, ventral siphuncles that are empty except in Karoceras. Siphuncle segments are inflated ventrally but straight dorsally. Septal necks are cyrtochoanitic, outwardly curved; connecting rings are thin.
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.
Hipparionoceras is a genus of oncocerids from the middle Devonian of Europe, North America, and China that lived around 395 million years ago.
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