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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] |
Tajaroceras
''Tajaroceras'' is an extinct slender cephalopod from the uppermost Lower Ordovician of western North America, belonging to the Orthocerid family Troedssonellidae. Background The shell of ''Tajaroceras'' is smooth and straight. The siphuncle which is at least 0.35 the shell diameter is subcentral. Septal necks are short and the connecting rings are thin and homogeneous. The distinguishing feature of Tajaroceras lies within its siphuncle. Along the ventral side, within the siphuncle, is a continuous rod, much like that found in a group known as 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 .... On the dorsal side, overlying within, are annular deposits that grow forward to form a continuous lining that ultimately rests against the ventral rod, leaving a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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] |
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] |
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] |
Narthecoceratidae
''Narthecoceratidae'' is an extinct family of orthocone cephalopods who lived in marine environments in what is now North America during the Ordovician from 460.5—449 mya, existing for approximately . Taxonomy Narthecoceratidae was named by Flower (1958). It was assigned to ''Endocerida'' by Teichert et al. (1964); and reassigned to ''Orthocerida'' by Frey (1981).R. C. Frey. 1981. Narthecoceras (Cephalopoda) from the Upper Ordovician (Richmondian) of Southwest Ohio. Journal of Paleontology 55(6):1217-1224 Morphology The shell is usually long, and may be straight ("orthoconic") or gently curved. In life, these animals may have been similar to the modern squid, except for the long shell. Fossil distribution Fossil distribution includes Ohio, Franklin District, Canada, and Manitoba, Canada , image_map = Manitoba in Canada 2.svg , map_alt = Map showing Manitoba's location in the centre of Southern Canada , Label_map = yes , c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Treatise On Invertebrate Paleontology
The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and extant (still living) invertebrate animals. The prehistoric invertebrates are described as to their taxonomy, morphology, paleoecology, stratigraphic and paleogeographic range. However, taxa with no fossil record whatsoever have just a very brief listing. Publication of the decades-long ''Treatise on Invertebrate Paleontology'' is a work-in-progress; and therefore it is not yet complete: For example, there is no volume yet published regarding the post-Paleozoic era caenogastropods (a molluscan group including the whelk and Common periwinkle, periwinkle). Furthermore, every so often, previously published volumes of the ''Treatise'' are revised. Evolution of the proje ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endocerida
Endocerida is an extinct nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in their siphuncle. Endocerida was a diverse group of cephalopods that lived from the Early Ordovician possibly to the Late Silurian. Their shells were variable in form. Some were straight (orthoconic), others curved (cyrtoconic); some were long (longiconic), others short (breviconic). Some long-shelled forms like '' Endoceras'' attained shell lengths close to . The related ''Cameroceras'' is anecdotally reported to have reached lengths approaching , but these claims are problematic. The overwhelming majority of endocerids and nautiloids in general are much smaller, usually less than a meter long when fully grown. Morphology Endocerids had a relatively small body chamber as well as a proportionally large siphuncle, which in some genera reached nearly half the shell diameter. This suggests that much of the visceral mass may have been housed within the siphuncle ... [...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] |
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, existing for approximately . Taxonomy Baltoceratidae was named by Kobayashi (1935) and assigned to the Ellesmeroceratida by Flower and Kummel (1950) where it was retained by Unklesbay and Young (1956), again by Flower (1964)Flower 1964. The Nautiloid Order Ellesmeroceratida (Cephalopoda), Memoir 12, New Mexico Bureau of Mines and Mineral Resources, Socorro, NM , and by Furnish and Glenister in Teichert et al. (1964).Teichert et al 1964, Treatise on Invertebrate Paleontology Part K Mollusca 3, Nautiloidea-Ellesmerocerida by Furnish and Glenister, K129- K153 Flower (1964) included the Baltoceratidae in the ellesmeroceratid suborder Ellesmeroceratina. Further study of baltoceratid interiors, namely regarding the generally thin connecting r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
