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Polyelasmoceratidae
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. The Middle Silurian ''Danaoceras ''Danaoceras'' is a nautiloid cephalopod from the middle Silurian of central Europe included in the oncoceroid family Polyelasmoceratidae. Similar specimens from the middle Devonian of North America may belong. ''Danaoceras'' has a laterally co ...'' is probably the ancestral genus, which give rise to the contemporary '' Codoceras'' and ultimately the subsequent Devonian genera. References * Walter C. Sweet, 1964. Nautiloidea - Oncocerida; Treatise on Invertebrate Paleontology, Part K. G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Danaoceras
''Danaoceras'' is a nautiloid cephalopod from the middle Silurian of central Europe included in the oncoceroid family Polyelasmoceratidae. Similar specimens from the middle Devonian of North America may belong. ''Danaoceras'' has a laterally compressed shell curved such that the ventral or siphuncular side is longitudinally concave, i.e. is endograstric. The siphuncle, which is ventrally submarginal, contains laminar actinosiphonate deposits. ''Danaoceras'' is the ancestral genus of the Polyelasmoceratidae and is possibly derived from either ''Oonoceras'' or ''Oocerina'' of the 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, cyrtocon ... based on similarities of the siphuncle References * Walter C. Sweet, 1964. Nautiloidea - Oncocerida; Treatise on Invertebrate Paleontology ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Codoceras
''Codoceras'' is a genus of nautiloids belonging to the Polyelasmoceratidae, an Oncocerida family. ''Codoceras'', known from the Silurian of Europe, has a compressed, rapidly enlarging shell, curved endogastrically such that the presumed ventral side is concave and the opposite dorsal side is convex. The siphuncle is displaced from the center slightly toward the venter. Early segments are cylindrical. Later ones are nummuloidal and broader. The type species is ''Cyrtoceras indominum'' Barrande 1866. ''Danaoceras ''Danaoceras'' is a nautiloid cephalopod from the middle Silurian of central Europe included in the oncoceroid family Polyelasmoceratidae. Similar specimens from the middle Devonian of North America may belong. ''Danaoceras'' has a laterally co ...'' is closely related and its most likely ancestor. References * Walter C. Sweet, 1964. Nautiloidea - Oncocerida; Treatise on Invertebrate Paleontology, Part K. Geological Society of America and University of Kansas Press ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macrodomoceras
''Macrodomoceras'' is a genus of oncocerids, family Polyelasmoceratidae, from the Middle Devonian of Australia. The shell of ''Macrodomoceras'' is a compressed, endogastric cyrtocone, i.e. section higher than wide and curved with the ventral side concave, with a subtriangular cross section. The siphuncle is ventral, marginal, with continuous actinosiphonate lamellae. ''Macrodomoceras'' resembles ''Danaoceras ''Danaoceras'' is a nautiloid cephalopod from the middle Silurian of central Europe included in the oncoceroid family Polyelasmoceratidae. Similar specimens from the middle Devonian of North America may belong. ''Danaoceras'' has a laterally co ...'' in its subtriangular cross section, but its sutures have bluntly pointed ventral saddles. References * Walter C. Sweet, 1964. Nautiloidea - Oncocerida; Treatise on Invertebrate Paleontology, Part K. Geological Society of America. Prehistoric nautiloid genera Oncocerida {{paleo-nautiloidea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wadeoceras
''Wadeoceras'' is a genus of nautiloids included in the Polyelasmoceratidae, a family of oncocerids living from the Middle Silurian to the Late Devonian. The phragmocone The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae. In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a ... of ''Wadeoceras'' is cyrtoconic (curved) and the living chamber, more orthoconic (straight). References * Walter C. Sweet, 1964. Nautiloidea -Oncocerida, Treatise on Invertebrate Paleontology, Part L, Mollusca 3. Geological Society of America and University of Kansas Press. Prehistoric nautiloid genera Silurian first appearances Late Devonian animals Late Devonian genus extinctions Oncocerida {{paleo-nautiloidea-stub ... [...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] |
Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out. One important event in this period was the initial establishment of terrestrial life in what is known as the Silurian-Devonian Terrestrial Revolution: vascular plants emerged from more primitive land plants, dikaryan fungi started expanding and diversifying along with glomeromycotan fungi, and three groups of arthropods (myriapods, arachnids and hexapods) became fully terrestrialized. A significant evolutionary milestone during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, where rocks from this period were first studied. The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. The arthropod groups of myriapods, arachnids and hexapods also became well-established early in this period, after starting their expansion to land at least from the Ordovician period. Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fishes. The placoderms began dominating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hipparionoceras
''Hipparionoceras'' is a genus of oncocerids from the middle Devonian of Europe, North America, and China that lived around 395 million years ago. The shell of ''Hipparionoceras'' is curved, rapidly expanding, flared toward the aperture. The curvature is endogastric with the ventral side somewhat concave in profile. The siphuncle is subventral, empty, with segments expanded into the short but broad chambers. Septa are close spaced, their curvature shallow. '' Polyelasmoceras'' and ''Macrodomoceras'' are related genera, also from the Middle Devonian. ''Cadoceras'' from the Middle Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ... may be ancestral. References * Walter C. Sweet, 1964. Nautiloidea-Oncocerida. Treatise on Invertebrate Paleontilogy, Part K. Geological Society ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyelasmoceras
''Polyelasmoceras'' is an extinct genus of nautiloid from the Early Devonian, between 408 and 393 million years ago. The holotype specimen is held by Museums Victoria and was collected near Murrindal in Victoria Victoria most commonly refers to: * Victoria (Australia), a state of the Commonwealth of Australia * Victoria, British Columbia, provincial capital of British Columbia, Canada * Victoria (mythology), Roman goddess of Victory * Victoria, Seychelle .... There is a single species, ''Polyelasmoceras aduncum''. References Prehistoric nautiloid genera Oncocerida {{paleo-nautiloidea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
