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Apocrinoceratidae
Apocrinoceratidae constitutes a family of Middle Ordovician nautiloid cephalopods characterized by straight or slightly curved, transversely ribbed shells having siphuncles composed of expanded segments, short recurved septal necks, and thick connecting rings. Derivation is from the Protocycloceratidae, a family of ellesmerocerids, which differ in having straight or concave siphuncle segments, but are otherwise similar in form. Apocrinoceratidae was established by Rousseau Flower (in Flower & Teichert, 1957) repeated in Flower (1964) for the genus '' Apocrinoceras'' (Teichert & Glenister, 1954). Four additional genera are included; '' Desioceras'' and '' Glenisteroceras'' (Flower and Teichert 1957, Flower 1964),'' Bakeroceras'' (Hook and Flower 1977), and '' Paldoceras'' (Kröger ''et al'' 2009). Apocrinoceratidae was removed from the Ellesmerocerida to the Discosorida Discosorida are an order of cephalopods that lived from the beginning of the Middle Ordovician, through the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ellesmerocerida
The Ellesmerocerida is an order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician. Morphology The Ellesmerocerida are characterized by shells that are typically small, some even tiny, with close-spaced septa and relatively large ventral siphuncles. In some genera (e.g. '' Paleoceras''), the septa are uniformly spaced. Shells of ellesmerocerids are typically smooth and compressed and vary in form. They may be breviconic (short) or longiconic (elongate), straight (orthoconic) or curved (cyrtoconic). Cyrtoconic forms are usually endogastric, with longitudinally convex ventral margins. The apeces of straight forms typically have an endogastric curvature. Some may have grown to as much as 15 cm. Siphuncle segments are tubular or concave. Septal necks are short. Connecting rings which may appear layered are thick and typically wedge shaped with their maximum width at or near where ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paldoceras
''Paldoceras'' is a genus of nautiloid cephalopods found in the middle Ordovician of Estonia and Sweden, included in the discosorid family Apocrinoceratidae. Two species are recognized; ''Paldoceras paldiskense'' found northwest of Paldiski in northern Estonia and ''Paldoceras neptunsakerense'' found on Öland Island, Sweden. Shells are small, on the order of a few centimeters in length at most, gently expanding and moderately endogastric with the 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 ... lying along the inner concave curvature of the shell. Septa are close spaced, less than a millimeter. Siphuncle segments are broadly expanded. Septal necks in ''paldiskense'' are short and generally cyrtochoanitic (flared outwardly). Those in ''neptunsakerense'' are suborthoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protocycloceratidae
Protcycloceratidae is an extinct family of slender, commonly annulate, members of the cephalopod order Ellesmerocerida that lived during the Early Ordovician. Protocycloceratidae, named by Kobayashi (1935), are characterized by transversely ribbed, elongate shells that may be straight or slightly curved, as to be either endogastric or exogastric.Flower 1964, Furnish & Glenister 1964 Although not universally accepted, Kröger and Mutvie (2005) revised the Protocycloceratidae to include only those ellesmerocerids that have straight transverse sutures and siphuncles with concave segments and thick connecting rings. Protocycloceratidae (''sensu'' Flower, 1964) includes the follow genera, given with brief descriptions. *'' Protocycloceras''. Strongly annulate orthocones; cross section circular; annulations and sutures transverse and essentially straight; siphuncle tubular, ventral but not marginal, about 0.3 corresponding shell diameter. Lower Ordovician, cosmopolitan. *'' Catoraphi ... [...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] |
Glenisteroceras
''Glenesteroceras'', which is of questionable validity, is based on a single specimen from the Lower Ordovician of New York state, described by Rousseau Flower, 1957. ''Glenestoceras'' is described as being a weakly annulate orthocone with a circular cross section and large central siphuncle with slightly divergent necks, thick connecting rings, and expanded segments. Description is based on an incomplete immature phragmocone with a 5mm cross section. References * Walter A Sweet, 1964. Nautiloidea - Orthocerida, ''Treatise on Invertebrate Paleontology'', Part K, ''incl'' Nautiloidea. Geological Society of America and University of Kansas Press. Prehistoric nautiloid genera {{paleo-nautiloidea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Middle Ordovician First Appearances
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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Middle Ordovician Extinctions
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] |
Prehistoric Nautiloid Families
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] |
