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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] |
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] |
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] |
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] |
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] |
Prehistoric Nautiloid Genera
Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use of symbols, marks, and images appears very early among humans, but the earliest known writing systems appeared 5000 years ago. It took thousands of years for writing systems to be widely adopted, with writing spreading to almost all cultures by the 19th century. The end of prehistory therefore came at very different times in different places, and the term is less often used in discussing societies where prehistory ended relatively recently. In the early Bronze Age, Sumer in Mesopotamia, the Indus Valley Civilisation, and ancient Egypt were the first civilizations to develop their own scripts and to keep historical records, with their neighbors following. Most other civilizations reached the end of prehistory during the following Iron Age. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
