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Westonoceratidae
Westonoceratidae are exogastric, mostly compressed, Discosorida of moderate size from the Middle Ordovician to the Lower Silurian. The siphuncle is typically close to the convexly curved outer margin of the phragmocone – the chambered part of the shell – taken to be ventral but may be more central in some genera. Connecting rings are thin to moderately thick with inflated bullettes grasping the previous septal foremina. Parietal deposits within the siphuncle from endocones in advanced genera and cameral deposits are found in some. The Westonoceratidae are derived from the Cyrtogomphoceratidae through the cyrtogomphoceratid, '' Ulrichoceras''. In turn, the Westonoceratidae gave rise to a small group of discosorids, the Lowoceratidae, which form an intermediary step before the Discosoridae. Two principal lineages have been identified, both stemming from the genus '' Teichertoceras'', a derivative of ''Ulrichoceras''. One goes simply from '' Westonoceras'' to '' Winnipeg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Winnipegoceras
''Winnipegoceras'' is an extinct nautiloid genus from the Ordovician belonging to the Order Discosorida. Phylogeny ''Winnipegoceras'' is included in the discosorid family Westonoceratidae and is derived from '' Westonoceras''. Westonoceratidae have mostly medium to large, compressed, exogastric shells with moderately sized siphuncles composed of short folded back septal necks and generally thin connecting rings with swollen bullettes and which contain internal linings. (Flower & Teichert 1957; Teichert 1964) Description ''Winnipegoceras'', named by Foerste (1922) for fossils found near Winnipeg in Manitoba, Canada, is known by it large, slender, compressed, strongly curved exogastric shells; long slender body chamber and siphuncle that is slightly removed from the venter which is the outer, longitudinally convex margin. Siphuncle segments are strongly narrowed at the septal foremina, bullettes swollen, parietal and other internal deposits rarely preserved. (ibid) See also * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Discosorida
Discosorida are an order of cephalopods that lived from the beginning of the Middle Ordovician, through the Silurian, and into the Devonian. Discosorids are unique in the structure and formation of the siphuncle, the tube that runs through and connects the camerae (chambers) in cephalopods, which unlike those in other orders is zoned longitudinally along the segments rather than laterally. Siphuncle structure indicated that the Discosorida evolved directly from the Plectronoceratida rather than through the more developed Ellesmerocerida, as did the other orders. Finally and most diagnostic, discosorids developed a reinforcing, grommet-like structure in the septal opening of the siphuncle known as the bullette, formed by a thickening of the connecting ring as it draped around the folded back septal neck. Evolution The origin of the Discosorida is unknown, thought at one timeRousseau H. Flower. 1964. The Nautiloid Order Ellesmerocerida (Cephalopods); relevant pages. Memoir 12 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ulrichoceras
''Ulrichoceras'' is recognised as the basal cyrtogomphoceratid genus, which is the source for the rest of the Cyrtogomphoceratidae as well as for the Westonoceratidae. The Cyrtogomphoceratidae are endogastric, the Westonoceratidae, exogastric. ''Ulrichoceras'' has a cyrtoconic, endogastric shell that expands fairly rapidly to the middle of the body chamber, then contracts toward the aperture. The cross section is slightly depressed, atypical for cyrtogomphoceratids but not so for Reudemannoceratids; dorsal and ventro lateral sides are broadly rounded, the venter moderately flattened. Sutures have broad ventral lobes. The siphuncle is between the center and the venter; segments are short and not strongly contracted at the septal foremina, connecting rings are thickened and have enlarged bullettes. ''Ulrichoceras'', named by Foerste, 1925, type ''U. beloitense'', comes from the Middle Ordovician of Wisconsin, U.S.A. It is intermediary in form between '' Reudemanoceras'' and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sinclairoceras
''Sinclairoceras'' is a nautiloid cephalopod in the discosorid family Westonoceratidae from the Middle Ordovician Simard Limestone of Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee .... The shell is laterally compressed, upwardly curved, and short; an exogastric brevicone with the venter narrowly and dorsum broadly rounded. The dorsum, at the upper surface, is only slightly concave longitudinally. The venter, at the lower surface, is more strongly convex longitudinally, drawing away from the dorsum and forming a hump at the anterior end of the phragmocone where ''Sinclairoceras'' reaches its greatest width. The upper and lower sides of the body chamber are essentially straight and virtually parallel, flaring slightly at the aperture. The sides however converge on the ape ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reedsoceras
''Reedsoceras'' is a genus of large discosorids (Nautiloidea) in the family Westonoceratidae from the middle and upper Ordovician of North America. ''Reedsoceras'' was named as a genus characterized by rapidly expanding exogastric cyrtocones with unconstricted apertures and straight sutures. The siphuncle is close to the venter, which is the externally convex side of the shell, and is composed of very short, broadly rounded segments. Structure of the siphuncle wall is unknown. ''Reedsoceras'' seems to be derived from '' Simardoceras'' and to be more closely related to a group that also includes ''Sinclairoceras'' than to other westonoceratids, especially those with long narrowing body chambers and bent back exogastric phragmocones like ''Winnipegoceras ''Winnipegoceras'' is an extinct nautiloid genus from the Ordovician belonging to the Order Discosorida. Phylogeny ''Winnipegoceras'' is included in the discosorid family Westonoceratidae and is derived from '' Westonoceras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyrtogomphoceratidae
The Cyrtogomphoceratidae are a family in the cephalopod order Discosorida that comprises genera commonly with compressed, endogastrically curved shells. Siphuncles lie close to the ventral side, segments are broadly inflated, connecting rings thick and apically expanded thick bullettes. Chambers are short, separated by shallow, dish shaped septa. Apertures are generally simple. The Cyrtogomphoceratidae are derived from the discosorid family Reudemannoceratidae, probably from '' Reudemannoceras'', through the ancestral genus '' Ulrichoceras'', and have a range from the Middle Ordovician to the Lower Silurian. The familyTeicher, C. 1964. Nautiloidea-Discosorida. Treatise on Invertebrate Paleontology, Part K. Teichert and Moore, eds. includes: :*'' Cyrtogomphoceras'' :*'' Kiaeroceras'' :*'' Konglungenoceras'' :*'' Landeroceras'' :*'' Parryoceras'' :*'' Strandoceras'' :*'' Ulrichoceras'' ''Ulrichoceras'' is also considered the source for the exogastric Westonoceratidae. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lowoceratidae
The Lowoceratidae is a small family of discosorids, early nautiloid cephalopods, from the Middle Silurian in which the characteristic bullette is found only in early growth stages. Lowoceratids were first found in Southampton Island in the Canadian arctic. The Lowoceratidae consists so far of only two genera, ''Lowoceras'' and ''Tuylocras'', named by Foerste and Savage in 1927 and combined by Flower in 1940 as the Lowoceratidae. Both are strongly compressed, exogastric brevicones with the ventral side more narrowly rounded than the dorsal. Shells enlarge moderately to the middle of the mature body chamber, then contract gently toward the aperture. The siphuncle in each is slightly removed from the ventral margin. The siphuncle of ''Tuyloceras'', genotype ''T. percurvatum'', starts off with slender, subquadrate segments with thick rings and swollen bullettes, but later in life the segments become expanded, rings thinner, and bullettes simple and unswollen. ''Lowoceras'', gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Teichertoceras
''Teichertoceras'' is a discosorid genus in the family Westonoceratidae characterized by an endogastric curvature to the early portion of the phragmocone. The shell of ''Teichertoceras'' is moderately compressed, the early portion a narrow expanding cyrtocone that in the adult become more swollen, taking on an exogastric aspect. The body chamber in the adult is contracted toward the aperture. The siphuncle is ventral. Bullettes at the adapical ends of the connecting rings are small. ''Teichertoceras'' is thought to have given rise to '' Westonoceras'' and ''Faberoceras'' and to be derived from ''Ulrichoceras ''Ulrichoceras'' is recognised as the basal cyrtogomphoceratid genus, which is the source for the rest of the Cyrtogomphoceratidae as well as for the Westonoceratidae. The Cyrtogomphoceratidae are endogastric, the Westonoceratidae, exogastric. ' ...''. It is found in geological formations of Middle Ordovician age in North America. References * Teichert, C. 1964. ''Nau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Westonoceras
''Westonoceras'' is an extinct nautiloid genus from the Discosorida that lived during the Middle and Late Ordovician that has been found in North America, Greenland, and Northern Europe. It is the type genus for the Westonoceratidae Description The shell of ''Westonoceras'' forms a humped exogastric cyrtocone with its greatest height (gibbosity) at the anterior part of the mature phragmocone and posterior body chamber. The early juvenile portion is slender, gently exogastric or straight and rapidly increasing in size. Curvature increases during development. The dorsum, on the longitudinally concave side, is broadly rounded. The venter, on the longitudinally convex side, is narrow. The siphuncle is located close to the ventral wall. Segments are box-shaped and strongly expanded. Septal necks are strongly recumbent; connecting rings thick, with inflated bullettes. Parietal deposits grow forward from the septal foremina, commonly forming a continuous internal lining. Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simardoceras
''Simardoceras'' is a genus in the discosorid (nautiloid cephalopod) family Westonoceratidae from the Middle Ordovician of Quebec. The shell of ''Simardoceras'' is a moderately expanding exogastric cyrtocone, said to resemble a rather large ''Oncoceras'', but with a siphuncle that is definitely discosorid. The venter is almost uniformly convex in longitudinal profile. The dorsal profile changes from concave in the apical portion to straight, then slightly convex at the front of the phragmocone and back of the body chamber, the concave again near the aperture. The siphuncle is ventral. Segments are subquadrate in outline and are longer than broad. Connecting rings are thick. Although ''Simardoceras'' somewhat resembles ''Winnipegoceras'' is the form of its siphuncle, it differs in its very broad cross section. The slender siphuncle segments also distinguish it from the apparently more closely related ''Sinclairoceras'' and from its apparent derivative ''Reedsoceras ''Reedsocera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clarkesvillia
''Clarkesvillia'' is a genus of Upper Ordovician westonocerids that differs from ''Faberoceras'' in having a more flattened venter and from the later '' Glyptodendron'' in having a more ventrally located siphuncle. References * Teichert, C. 1964. Nautiloidea -Discosorida. 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 co ... Part K Teichert and Moore, eds. Clarkesvillia-Paleobiology DB Prehistoric nautiloid genera Discosorida {{paleo-nautiloid-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glyptodendron
''Glyptodendron'' is a Lower Silurian westonocerid characterized by compressed cyrtocones with a narrowly rounded dorsum and greatest width in the ventrolateral region. Sutures slope forward from the dorsum which is on the longitudinally concave side. The siphuncle is slightly ventral from the center. Segments are subspherical in the young; equally broad but shorter in the adult. No endosiphuncular deposits are known. The surface of the shell is covered by obliquely intersecting rows of scale-like pits. It was first described by E. W. Claypole as part of a "tree-like fossil plant" thought to be similar to '' Lepidodendron''. The type material is from Eaton in Preble County, Ohio. Its generic etymology is modified from the Greek ''glypto'' (γλύφω) for "I engrave" and it "alludes to the depressed areoles" which Claypole erroneously interpreted from the superficial pits across the shell as being similar to those seen in lycopsid plants. Its specific epithet refers to it the lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |