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Selkirkoceras
''Selkirkoceras'' is a genus of armonoceratid cephalopods similar to ''Kochoceras'' of the Actinoceratidae, but with recumbent septal necks. The first siphuncular segment is large, broad, and blunt. ''Selkirkoceras'', which is known from the Middle Ordovician of western North America, is included in the '' Nybyoceras'' branch of the Armenoceratidae The Armenoceratidae are a family of early Paleozoic nautiloid cephalopods belonging to the order Actinocerida.Flower 1957.Studies of the Actinoceratida.; Memoir 2; New Mexico Bureau of Mines and Mineral Resources, Socorro, NM Teichert 1964. Act ... (Teichert, 1964), which also includes ''Nybyoceras'' and '' Megadisocosorus''. References * Curt Teichert, 1964. Actinoceratoidea, Treatise on Invertebrate Paleontology, Part K. Geological Society of America and University of Kansas Press. Prehistoric nautiloid genera Actinocerida {{paleo-nautiloidea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Armenoceratidae
The Armenoceratidae are a family of early Paleozoic nautiloid cephalopods belonging to the order Actinocerida.Flower 1957.Studies of the Actinoceratida.; Memoir 2; New Mexico Bureau of Mines and Mineral Resources, Socorro, NM Teichert 1964. Actinoceratoidea, Treatise on Invertebrate Paleontology, part K.(Nautiloidea) The Armenoceratidae, established by Troedsson (1926) are characterized by large, straight, or slightly curved shells and large siphuncles with strongly expanded segments between the septa. Septal necks are short and abruptly recurved along brims. Radial canals in the endosiphuncular canal system are typically arched, curving forward and backward from near the septal foramina (openings) to connect with the parispatium on either side of the middle of each segments. The parispatium is the narrow opening between the inner side of the connecting rings in actinocerids and the internal siphuncular deposits that grow forward and back from the region of the septal open ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nybyoceras
''Nybyoceras'' is an actinocerid genus assigned to the Armenoceratidae and similar to ''Armenoceras'' except for having a siphuncle close to the ventral side of the shell. Morphology As with ''Armenoceras'', ''Nybyoceras'' has a medium to large, straight shell.(Teichert 1964) Its primary diagnostic feature is its ventral siphuncle which the septa across obliquely.(Flower 1957,Teichert 1964) Ventrally, the septal necks are short and free, or recumbent for a short distance. Dorsally the brims are definitely recumbent.(Flower 1957) The connecting rings are broadly adnate to the septa ventrally at the posterior ends of the segments and dorsally at the anterior (adoral) ends.(Teichert 1964) Flower (1957) described the canal system within the siphuncle as being primarily of the single arc type, like ''Armenoceras'', and with interconnecting tubes. Teichert (1964) describes the canal system as being reticulate to curved and branching. Phylogengy and distribution ''Nybyoceras'' is de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megadisocosorus
''Megadisocosorus'' is a genus of actinocerid cephalopods similar to ''Armenoceras'' but with a short, slightly curved, breviconic shell. The siphuncle is in contact with the ventral wall, unlike that of ''Armenoceras'' in which the siphuncle is close to the center. ''Megadisocosorus'' is known from the Middle Silurian of North America. According to Teichert, 1964, ''Megadisocosorus'' is a member of one of the two branches of the Armenoceratidae that also includes ''Nybyoceras'' and ''Selkirkoceras ''Selkirkoceras'' is a genus of armonoceratid cephalopods similar to ''Kochoceras'' of the Actinoceratidae, but with recumbent septal necks. The first siphuncular segment is large, broad, and blunt. ''Selkirkoceras'', which is known from the Mid ...''. References * Curt Teichert, 1964. Actinoceratoidea, Treatise on Invertebrate Paleontology, Part K. Geological Society of America and University of Kansas Press. Prehistoric nautiloid genera Actinocerida {{paleo-nautiloidea ... [...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] |
Kochoceras
''Kochoceras'' is an extinct nautiloid genus from the later Ordovician belonging to the family Actinoceratidae and found in North America. Morphology ''Kochoceras'' is relatively short, breviconic, and grew to be fairly large with a shell more rapidly expanding than in ''Actinoceras''. The ventral, or under, side is strongly flattened with prominent lobes that may give the impression of ''Lambeoceras''. However septa in ''Kochoceras'' are more widely spaced and the siphuncle, which is proportionally very large, is in broad contact with the ventral wall. The siphucle in ''Lambeoceras'' is proportionally much smaller and is removed about one diameter from the ventral wall. The diameter of the siphuncle in the apical part of ''Kochoceras'' is 3/4 or more that of the shell. The siphuncle of ''Kochoceras'' is similar to that of ''Actinoceras'', the main difference between the two being that ''Kochoceras'' is breviconic (short) and has a narrow stratigraphic range, while ''Actinocera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Actinoceratidae
The Actinoceriatidae are a family of actinocerids named by Saemann in 1853 for those that grew to have large shells with blunt apices and large siphuncles with widely expanded segments and a generally arcuate endosiphucular canal system.Teichert 1964. Actinoceratoidea, Treatise on Invertebrate Paleontology, part K.(Nautiloidea) Their range is from the upper Middle Ordovician to the Lower Silurian. Actinocerids are generally straight-shelled nautiloid cephalopods with a siphuncle composed of expanded segments, typically with thin connecting rings, in which the internal deposits are penetrated by a system of canals Actinoceratids are derived from ''Wutinoceras'', possibly through an early '' Armenoceras'' or through '' Nybyoceras''Flower 1957.Studies of the Actinoceratida; Memoir 2; New Mexico Bureau of Mines and Mineral Resources, Socorro, NM and give rise to ''Lambeoceras'' and to the Huroniidae. Seven genera are included in the Actinoceratidae, ''Actinoceras'', '' Flowerocer ... [...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] |
