|
Trocholitidae
The Trocholitidae are Tarphycerida with whorls in close contact as with the Tarphyceratidae, but in which the siphuncle, similar in structure, becomes dorsal. The Trocholitidae are derived from the Tarphyceratidae, perhaps from different tarphyceratids. Members of the Trocholitidae vary in whorl section and siphuncle position. Most are tightly coiled with the dorsum impressed to some degree. As exceptions ''Arkoceras'' and ''Wichitoceras'' have their whorls touching but without a dorsal impression. '' Discoceras'' and '' Curtoceras'' have somewhat subquadrate whorl sections and are moderately impressed. In ''Graftonoceras'' and ''Jasperoceras'' the venter is rounded and continues smoothly through the flanks to a broad dorsum which in each is moderately impressed. The siphuncle in ''Graftonoceras'' is on the dorsal margin, in ''Jasperoceras'' it is between the center and dorsum. Whorls in T''rocholites'' have a wide cross section and low profile, in ''Wichitoceras'' they are lat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tarphycerida
The Tarphycerida were the first of the coiled cephalopods, found in marine sediments from the Lower Ordovician (middle and upper Canad) to the Middle Devonian. Some, such as '' Aphetoceras'' and '' Estonioceras'', are loosely coiled and gyroconic; others, such as '' Campbelloceras'', '' Tarphyceras'', and '' Trocholites'', are tightly coiled, but evolute with all whorls showing. The body chamber of tarphycerids is typically long and tubular,Furnish and Glenister 1964; Nautiloidea - Tarphycerida; In the ''Treatise on Invertebrate Paleontology'' Vol K; Teichert and Moore, (eds) GSA and U of Kansas Press 1964 as much as half the length of the containing whorl in most, greater than in the Silurian Ophidioceratidae. The Tarphycerida evolved from the elongated, compressed, exogastric Bassleroceratidae, probably ''Bassleroceras'', around the end of the Gasconadian through forms like ''Aphetoceras''. Close coiling developed rather quickly, and both gyroconic and evolute forms are fou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Discoceras
''Discoceras'' is an extinct marine cephalopod mollusk, a member of the Trocholitidae in the Tarphycerida. It is distinct from '' Discosorus'', It is characterized by closely coiled, gradually expanding shells with a subquadrate cross section, that may be ribbed or smooth. The sides are broadly rounded; the venter is wide and slightly rounded. The maximum width is slightly dorsal of the middle. The dorsum has a slight to moderate impression. The siphuncle starts off central for the first half whorl then becomes marginodorsal in the succeeding two whorls, then subdorsal at maturity. As with '' Trocholites'', the dorsal siphuncle in ''Discoceras'' probably indicates an orientation during life that places the back of the living chamber high in the shell.''Discoceras'', p K360 in Vol K of the ''Treatise on Invertebrate Paleontology'' in the section on the Trocholitidae, pp K359-K362, in the Chapter on the Tarphycerida by Furnish and Glenister starting with page K343. ''Discocer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trocholites
''Trocholites'' is a tarphycerid genus in the family Trocholitidae from the Middle and Late Ordovician with a gradually expanding, weakly ribbed shell; whorls in contact, dorsum slightly impressed; cross section depressed, venter and sides rounded; siphuncle close to but not at the dorsal margin. The dorsal siphuncle of ''Trocholites'', and the Trocholitidae is somewhat anomalous and may indicate something about the orientation of the shell during life; placing the last septum high rather than midway or low, typical of most. The prevailing location in most coiled cephalopods is central or ventral, extremely ventral in most ammonoids. '' Trochoceras'', of similar name, is a member of the Rutoceratidae in the Nautilida, and therefore only very distantly related back through the Bassleroceratidae The Bassleroceratidae is a family of gradually expanding, smooth ellesmerocerids with a slight to moderate exogastric curvature, subcircular to strongly compressed cross section, and ven ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Litoceras
''Litoceras'' is a trocholitid (Tarphycerida) genus that has been found in the Lower and Middle Ordovician of Newfoundland. Whorls in ''Litoceras'' have a broadly rounded cross section with its width greater than its height. Litoceras somewhat resembles the tarphyceratid ''Pionoceras'' from the same time, except for 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 ... being dorsal and in the center. Species Species within the genera ''Litoceras'' include: * '' Litoceras calciferum'' (Billings, 1865) * '' Litoceras versutum'' (Billings, 1865) * '' Litoceras whiteavsi'' Hyatt, 1894 References *Furnish, W.M and Glenister, Brian F (1964); Nautiloidea -Tarphycerida in the Treatise on Invertebrate Paleontology, Part L, Nautiloidea, Geological Society of America and Uni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tarphyceratidae
The Tarphyceratidae are tightly coiled, evolute Tarphycerida with ventral siphuncles. The dorsum is characteristically impressed where the whorl presses against the venter of the previous. The Tarphyceratidae are derived from ''Bassleroceras'' or possibly from some member of the Estonioceratidae. Tarphyceratids vary in form and siphuncle position. The siphuncle may be subcentral as in ''Centrotarphyceras''; intermediary as in '' Tarphyceras'', or subventral as in '' Campbelloceras''. Cross sections vary. ''Tarphyceras'' and ''Campbelloceras'' are rounded. ''Centrotarphyceras'' is subquadrate with broadly rounded flanks and a slightly rounded venter. ''Eurystomites'' is subquadrate and slightly compressed, with the maximum width closer to the dorsum. ''Pionoceras'' is subrounded and slightly depressed with the maximum width closer to the venter. The dorsal impression in ''Tarphyceras'' and ''Eurystomites'' is broad and deep and in ''Pionoceras'' and ''Centrotarphyceras'', broad an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Curtoceras
''Curtoceras'' is a genus in the tarphycerid family Trocholitidae found widespread in the late Early and Middle Ordovician of North America and northern Europe. ''Curtoceras'' has a shell that is gradually expanded, with half the fully mature body chamber divergent from the preceding volution. Whorl sections are near equidimentional with the inner margin (dosum) moderately impressed. The surface may be smooth or weakly ribbed. The siphuncle is ventral in the initial chamber and becomes dorsal after one volution. With the exception of the dorsal siphuncle, ''Curtoceras'' is somewhat similar to the tarphyceratid '' Campbelloceras'' See also *List of nautiloids References *Furnish, W.M. and Glenister, Brian F 1964; Nautiloidea -Tarphycerida, in 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, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beekmanoceras
''Beekmanoceras'' is a small cephalopod from the Middle Canadian Epoch of New York with a loosely coiled, gyroconic, shell in which the whorls are not in contact and the siphuncle is on the inner or concave side of the whorl. Furnish and Glenister (1964) placed ''Beekmanoceras'' in the Trocholitidae (Tarphycerida), interpreting the curvature to be ventral side convex, i.e. exogastastric and the siphuncle to be dorsal. Flower (1964) included ''Beekmanoceras'' in the Ellesmeroceratidae believing the siphuncle to be ventral and the curvature to be endogastric with the ventral side concave. Structural details of the genotype ''Beekmanoceras priscum'' the only species known, are obscure, allowing for different interpretations (ibid). A few things can be said however. No other trocholitids are known to have an openly coiled gyroconic shell which casts doubt on that placement. On the other hand, no endogastric forms are known for sure to have developed the kind of gyroconic coiling found ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hardmanoceras
''Hardmanoceras'' is a tarphycerid genus belonging to the Trocholitidae from the upper Lower Ordovician to possibly the lower Middle Ordovician, found in Western Australia. ''Hardmanoceras'' is like ''Discoceras ''Discoceras'' is an extinct marine cephalopod mollusk, a member of the Trocholitidae in the Tarphycerida. It is distinct from '' Discosorus'', It is characterized by closely coiled, gradually expanding shells with a subquadrate cross section, ...'' but prominently ribbed and with a depressed whorl section. The body, or living, chamber is long, 1 1/8 volutions long. The ultimate portion is slightly divergent, not an uncommon characteristic of tarphycerids. ''Harmanoceras'' was named by Teichert and Glenister in 1952. The type us ''Hardmanoceras lobatum''. References * W.M Furnish and Brian H Glenister, 1964. Nautiloidea-Tarphycerida. Treatise on Invertebrate Paleontology, Part K, Mollusca 3. Teichert and Moore, eds. Geol Soc of America and Univ Kansas Press. ... [...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] |
Cephalopod Families
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology. Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids. The class now contains two, only distantly related, extant subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish; and Nautiloidea, represented by ''Nautilus'' and ''Allonautilus''. In the Coleoidea, the molluscan shell has been internalized or is absent, whereas in the Nautiloidea, the external shell remains. About 800 living species of cephalopods have been ident ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Cephalopod Families")