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Nothoceratidae
Nothoceratidae is a family of nautiloid cephalopods in the orthoceratoid order Oncocerida in which shells are exogastrically or endogastrically breviconic, planospiral, or torticonic; often with a constricted or visored aperture; and a siphuncle commonly composed of concave segments and occupied by actinosiphonate deposits. Some ten genera have been described which lived during the time between the Early Silurian and Late Devonian. The ancestral form is probably '' Perimecoceras'' which is known from the Upper Silurian of central Europe and which is similar in external form the ''Oonoceras'' from the Oncoceratidae. Genera *'' Blakeoceras'' *'' Bolloceras'' *'' Conostichoceras'' *'' Cyrthoceratites'' *'' Lorieroceras'' *'' Metaphragmoceras'' *'' Mutoblakeoceras'' *'' Nothoceras'' *'' Paraconradoceras'' *'' Perimecoceras'' *'' Tafilaltoceras'' *'' Turnoceras'' References * Sweet, W. C. 1964; Nautiloidea -Oncocerida; Treatise on Invertebrate Paleontology The ''Treatise ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perimecoceras
''Perimecoceras'' is a genus of nothoceratids, nautilitoids in the order Oncocerida, with a slowly expanding, compressed, cyrtoconic shell, known from the Upper Silurian of central Europe. ''Perimecoceras'' is similar in general form to the oncoceratid genus '' Oonoceras'' from which it may have been derived, but differs in having a longer body chamber in proportion and in having concave segments to its siphuncle. It as also the most likely ancestral nothoceratid, probably giving rise to '' Blakeoceras'' and other Nothoceratidae. ''Perimecoceras'' probably lived on the sea floor, body chamber horizontal, phragmocone behind arched upward away from the bottom, using a combination of crawling and jet-swimming as it moved about. References * 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blakeoceras
''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. The shell of ''Blakeoceras'' is moderately curved (cyrtoconic) with the ventral side on the outer curvature (exogastric) Chambers in the phragmocone are short and wide, separated by straight, close spaced septa. Body chamber short. Siphuncle ventro-marginal, with internal, radial actinosiphonate deposits and concave segments. ''Blakeocers'' is similar to ''Perimecoceras'' in general form but is more broadly expanded and has a proportionally shorter body chamber. '' Conostichoceras'' is less strongly curved and widens more laterally. '' Turnoceras'' is more strongly curved and has a much greater expansion. ''Conostichoceras'' and ''Turnoceras'' are also more breviconic (shorter). ''Blakeoceras'' is an early nothoceratid possibly derived from ''Perimecoceras'' which has its or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conostichoceras
''Conostichoceras'' is a genus of exogastric, breviconic oncocerids included in the family Nothoceratidae, known from the Middle Devonian of central Europe and Upper Devonian of Australia.Sweet, W.C. 1964. Nautiloidea-Oncocerida Treatise on Invertebrate Paleontology part K. It probably lived on and swum above the sea floor. Morphology ''Conostichoceras'', named by Foeste, 1926, produced a depressed exogastric breviconic shell with short, wide chambers and large living chamber, similar to ''Blakeoceras'' and '' Turnoceras'' but differing details especially of the siphuncle. The siphuncle is ventral; nummuloidal in the adapical half of the phragmocone but with concave profiles in the adoral half, and is actinosiphonate. The sides of the living chamber in the adult converge slightly on the aperture. Taxonomy In its broader taxonomy ''Conostichoceras'' belongs to a group of nautiloid cephalopods known as the Nautilitoidea, a superorder that includes the orders Oncocerida, Tarphy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 thin and siphuncle segments are variably expanded (Flower, 1950). 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 (Sweet, 1964). Physical characteristics The shells of oncocerids are primarily somewhat compressed cyrtoconic brevicones. More advanced forms include gyrocones, serpenticones, torticones, and elongate orthocones and cyrtocones, reflective of the different families and genera (Flower, 1950; Sweet, 1964). The siphuncle in the Oncocerida is commonly located at or near the ventral margin. Connecting rings are mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oncoceratidae
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. Diagnosis Oncoceratidae are characterized by generally compressed, cyrtoconic, and breviconic shells with an exogastric curvature such that the ventral profile is convex or more so than dorsal, and in which the siphuncle is generally empty and located ventral of the center. In primitive forms, the siphuncle in early growth stages is composed of tubular segments with almost straight suborthochoanitic septal necks, but becomes cyrtochoanitic with expanded segments in the later growth stages, and is expanded and cyrtochoanitic throughout in advanced forms. In a few advanced forms, the siphuncle is actinosiphonate. (Flower 1950, Sweet 1964) Evolution The Oncoceratidae first appeared early in the Middle Ordovician (Sweet 1964) simultaneously with the Graciloceratidae, Tripteroceratidae, and Valcouroceratidae, deri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lorieroceras
''Lorieroceras lorieri'' is an extinct oncocerid nautilitoidean cephalopod belonging to the family Nothoceratidae. Fossils are found in Lower Devonian marine strata of France. Its shell is unusual among nautiloids in that it is a loosely coiled, turban-shaped helix that is sinistrally coiled. References *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 ; Geological Society of America and University of Kansas press; Teichert and Moore (eds). Sepkoski Cephalopod Genera Prehistoric nautiloid genera Fossil taxa described in 1926 Oncocerida {{paleo-Nautiloidea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turnoceras
''Turnoceras'' is a genus of Devonian cephalopods belonging to the oncocerid family Nothoceratidae. Its shell is broadly expanding and exogastrically curved such that the flattened dorsum is on longitudinally concave side. Aperture unconstricted with no hyponomic sinus for the water jet funnel. siphuncle along the outer, ventral, side, with radial, plate-like actinosiphonate deposits occupying the interior. ''Conostichoceras'' is similar externally, but has a siphuncle with a trapezoidal aspect to its siphuncle segments. ''Perimecoceras'' has similar concave siphuncle segments but is tubular in form. References * 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 ; Geological Society of A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
