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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] |
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] |
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] |
Nautiloidea
Nautiloids are a group of marine cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded species. They flourished during the early Paleozoic era, when they constituted the main predatory animals. Early in their evolution, nautiloids developed an extraordinary diversity of shell shapes, including coiled morphologies and giant straight-shelled forms ( orthocones). Only a handful of rare coiled species, the nautiluses, survive to the present day. In a broad sense, "nautiloid" refers to a major cephalopod subclass or collection of subclasses (Nautiloidea ''sensu lato''). Nautiloids are typically considered one of three main groups of cephalopods, along with the extinct ammonoids (ammonites) and living coleoids (such as squid, octopus, and kin). While ammonoids and coleoids are monophyletic clades with exclusive ancestor-descendant rela ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Middle Silurian
Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (other) * Middle Brook (other) * Middle Creek (other) * Middle Island (other) * Middle Lake (other) * Middle Mountain, California * Middle Peninsula, Chesapeake Bay, Virginia * Middle Range, a former name of the Xueshan Range on Taiwan Island * Middle River (other) * Middle Rocks, two rocks at the eastern opening of the Straits of Singapore * Middle Sound, a bay in North Carolina * Middle Township (other) * Middle East Music * "Middle" (song), 2015 * "The Middle" (Jimmy Eat World song), 2001 * "The Middle" (Zedd, Maren Morris and Grey song), 2018 *"Middle", a song by Rocket from the Crypt from their 1995 album ''Scream, Dracula, Scream!'' *"The Middle", a song by Demi Lovato from their debut album ''Don't Forget'' *"The Middle", a song by T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oonoceras
''Oonoceras'' is an extinct genus of fossil cephalopods included in the nautiloid order Oncocerida and the family Oncoceratidae from the Middle Ordovician to Middle Silurian of North America and Europe, arbitrarily included in the Slender Oncoceratidae. Shells of this genus are generally slender, gradually expanding, exograstric cyrtocones with an ovoid cross section more narrowly rounded ventrally than dorsally as in (e.g.) ''Bassleroceras''. Curvature is generally greater than that in ''Oocerina ''Oocerina'' is an extinct genus of nautiloid cephalopods that lived during the Late Silurian of Europe, Russia, and North America. ''Oocerina'', included in the oncoerid family Oncoceratidae and arbitrarily within the Slender Oncoceratidae, i ...'' but less than that of '' Richardonoceras'' or '' Dunleithoceras''. The siphuncle of ''Oonoceras'' is cyrtochoanitic. Septal necks flare outwardly and unlike ''Oocerina'', are empty. Segments are either slightly or broadly expanded i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oocerina
''Oocerina'' is an extinct genus of nautiloid cephalopods that lived during the Late Silurian of Europe, Russia, and North America. ''Oocerina'', included in the oncoerid family Oncoceratidae and arbitrarily within the Slender Oncoceratidae, is characterized by a moderately slender, elongate shell with an exogastric curvature, such that the lower side with the siphuncle is convex in profile and the opposite, upper, side is concave in profile. Shells are laterally compressed, curvature is gentle to almost straight. Chambers are short, septa close spaced, sutures typically straight. The siphuncle is nummuloidal, containing actinosiphonate deposits within. ''Oonoceras ''Oonoceras'' is an extinct genus of fossil cephalopods included in the nautiloid order Oncocerida and the family Oncoceratidae from the Middle Ordovician to Middle Silurian of North America and Europe, arbitrarily included in the Slender Oncoc ...'' is similar except for having a generally stronger curvature an ... [...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] |
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] |
