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Dissidocerida
Dissidocerida is an order of Early Ordovician to the Early Silurian orthoceratoid cephalopods in which the siphuncle has a continuous lining or a longitudinal rod-like structure within. The order Dissidocerida was proposed by Zhuravleva (1994) for ''Dissidoceras undosum'' Zhuravleva, 1964, a Silurian orthoconic genus with a wide, nearly central, tubular siphuncle, suborthochoanitic septal necks, and endosiphuncular rod; in many aspects similar to rod-bearing orthocones of the Ordovician. It is thought by some that Ordovician-Silurian orthocones with continuous longitudinal endosiphuncular laminar deposits constitute a single phylogenetic stock. The Dissidocerida as understood includes the Polymeridae, Rangeroceratidae, Troedssonellidae, and Dissidocertidae. The Polymeridae and Rangeroceratidae were proposed by Evans in 2005 for ''Polymeres'' Murchison 1839 and ''Rangeroceras'' Hook and Flower 1977, respectively. Troedssonellidae Troedssonellidae is a family of orthoce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthoceratoidea
Orthoceratoidea is a major subclass of nautiloid cephalopods. Members of this subclass usually have orthoconic (straight) to slightly cyrtoconic (curved) shells, and central to subcentral siphuncles which may bear internal deposits. Orthoceratoids are also characterized by dorsomyarian muscle scars (a small number of large scars concentrated at the top of the body chamber), extensive cameral deposits, and calciosiphonate connecting rings with a porous and calcitic inner layer. Currently, Orthoceratoidea comprises the orders Riocerida, Dissidocerida, Actinocerida, Pseudorthocerida, Lituitida and Orthocerida. Orthocerida is a noteworthy paraphyletic order which is ancestral to the major cephalopod groups such as the extinct ammonoids and living coleoids (cephalopods without external shells, including squids, octopus, cuttlefish, etc.). Taxonomy As a superorder, Orthoceratiodea was one of six superorders within the Nautiloidea, the others being the Plectronoceratoidea (= Ellesm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Troedssonellidae
Troedssonellidae is a family of orthoceroid cephalopods from the Ordovician, derived from rod-bearing Baltoceratidae, that have a continuous lining within the siphuncle that resembles very thin and slender endocones. Shells are generally slender and orthoconic. The siphuncle is central or subcentral, composed of straight or slightly expanded segments. Septal necks generally short and connecting rings are thin. Thin cameral deposits (lining the chambers) are known, which along with the position of the siphuncle and thin connecting rings distinguishes them from the endocerids in which they have been included.Flower 1976. Ordovician Cephalopod Faunas and Their Role in Correlation, in The Ordovician System: proceedings of a Palaeontological Association symposium, Sept 1974 Troedsonnellids first appear high in Lower Ordovician (Cassinian) strata, beginning with '' Tajaroceras'' and extend at least through the Whiterock Stage The Whiterockian, often referred to simply as the Whit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rangeroceratidae
Rangeroceratidae is a family of orthoceroid cephalopods known from the late Early Ordovician in eastern North America (New York and Quebec) and Great Britain, included in the order Dissidocerida. The family was named by Evans, 2005, and contains three genera: '' Rangeroceras'', '' Anrangeroceras'', and '' Cyclorageroceras''. Rangeroceratidae is based on the genus '' Rangeroceras'', named by Hook & Flower (1977); at that time considered a member of the rod-bearing Baltoceratidae Baltoceratidae is an extinct family of orthoconic cephalopods belonging to the subclass Nautiloidea endemic to what would be Asia, Australia, Europe, North America, and South America during the Ordovician living from about 480–460 mya, exist ... along with genera like '' Rhabdiferoceras'' and '' Veneficoceras''. References * Paleobiology DatabasRangeroceratidae* D. H. Evans. 2005. The Lower and Middle Ordovician cephalopod faunas of England and Wales. Monograph of the Palaeontographical Society 62 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The Ordovician, named after the Celtic Britons, Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same Rock (geology), rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed Stratum, strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Union of Geological Sciences, Intern ... [...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] |
Siphuncle
The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and ''Spirula''. In the case of the cuttlefish, the siphuncle is indistinct and connects all the small chambers of that animal's highly modified shell; in the other cephalopods it is thread-like and passes through small openings in the septa (walls) dividing the camerae (chambers). Some older studies have used the term siphon for the siphuncle, though this naming convention is uncommon in modern studies to prevent confusion with a mollusc organ of the same name. Function The siphuncle is used primarily in emptying water from new chambers as the shell grows. To perform this task, the cephalopod increases the saltiness of the blood in the siphuncle, and the water moves from the more dilute chamber into the blood through osmosis. At the sam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prehistoric Cephalopod Orders
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] |
Ordovician Cephalopods
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The Ordovician, named after the Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silurian Cephalopods
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 durin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
