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Phragmoceratidae
The Phragmoceratidae is a family of extinct nautiloid cephalopods from the Order Discosorida that lived during the latter part of the Silurian. Diagnosis Phragmoceratids are characterized by generally compressed, upwardly curved endogastric shells with slit-like apertures for egress and ventral siphuncles with broadly expanded segments, thick connecting rings, and small to vestigial bullettes. Phragmoceratids are morphologically similar in regards to their constricted apertures to the more cylindrical and orthoconic Mandaloceratidae, also discosorids, and to the oncocerid Hemiphragmoceratidae Hemiphragmoceratidae is a family of endogastrically brevconic oncocerids characterized by elaborately visored apertures in which the hyponomic sinus in mature specimens is on a spout-like process and there may be lateral and dorsal salients. (S ... (Sweet 1964); both which also come from the Silurian. Derivation The Phragmoceratidae are derived from the Ordovician Cyrtogomphocerat ... [...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] |
Hemiphragmoceratidae
Hemiphragmoceratidae is a family of endogastrically brevconic oncocerids characterized by elaborately visored apertures in which the hyponomic sinus in mature specimens is on a spout-like process and there may be lateral and dorsal salients. (Sweet 1964, Flower 1950). Shells are compressed with the apical portion curved and the anterior straight. Siphucles are nummuloideal with expanded spheroidal segments and continuously actinosiphonate interiors. The Hemiphragmoceratidae are probably descended from the Oncoceratidae and are known from the middle and upper Silurian but may range into the middle Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ... (Sweet 1964). They are similar with regards to their constricted and ornate apertures to the middle Silurian exogastric Trime ... [...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] |
Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out. One important event in this period was the initial establishment of terrestrial life in what is known as the Silurian-Devonian Terrestrial Revolution: vascular plants emerged from more primitive land plants, dikaryan fungi started expanding and diversifying along with glomeromycotan fungi, and three groups of arthropods (myriapods, arachnids and hexapods) became fully terrestrialized. A significant evolutionary milestone during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silurian First Appearances
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out. One important event in this period was the initial establishment of terrestrial life in what is known as the Silurian-Devonian Terrestrial Revolution: vascular plants emerged from more primitive land plants, dikaryan fungi started expanding and diversifying along with glomeromycotan fungi, and three groups of arthropods (myriapods, arachnids and hexapods) became fully terrestrialized. A significant evolutionary milestone during th ... [...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] |
Actinocerida
The Actinocerida are an order of generally straight, medium to large cephalopods that lived during the early and middle Paleozoic, distinguished by a siphuncle composed of expanded segments that extend into the adjacent chambers, in which deposits formed within contain a system of radial canals and a narrow space along the inner side of the connecting ring known as a paraspatium. (Teichert 1964) Septal necks are generally short and cyrtochoanitic, some being recumbent, some hook shaped. Most grew to lengths of about but some, like the Huroniidae of the Silurian grew significantly larger. Ecology The Actinocerida inhabited shallow to quite deep waters, where they alternated between swimming and lying on the bottom. They were predatory, and able to control their buoyancy to a greater degree than their contemporaries. Derivation The derivation of the Actinocerida remains enigmatic. They first appear late in the Early Ordovician (Cassinian Stage, late Floian) with the Georginida ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthocerida
Orthocerida is an order of extinct Orthoceratoid cephalopods also known as the Michelinocerida that lived from the Early Ordovician () possibly to the Late Triassic (). A fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous (). They were most common however from the Ordovician to the Devonian. Shell form 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. The internal structure of the shell consists of concavo-convex chambers linked by a centrally-placed tube called a siphuncle. There is a tendency for the chambers to develop cameral deposits, which were used as ballast to balance the long gas-filled shell. Depending on the family, the siphuncle has orthochoanitic (short and straight) or cyrtochoanitic (outwardly curved) septal necks, which protrude from the septa. The shell surface may be (depending on the specie ... [...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] |
Oncocerida
The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian (early Carboniferous; one possible member is known from the Early Permian), in which the connecting rings are thin and siphuncle segments are variably expanded (Flower, 1950). At present the order consists of some 16 families, a few of which, such as the Oncoceratidae, Brevicoceratidae, and Acleistoceratidae contain a fair number of genera each while others like the Trimeroceratidae and Archiacoceratidae are represented by only two or three (Sweet, 1964). Physical characteristics The shells of oncocerids are primarily somewhat compressed cyrtoconic brevicones. More advanced forms include gyrocones, serpenticones, torticones, and elongate orthocones and cyrtocones, reflective of the different families and genera (Flower, 1950; Sweet, 1964). The siphuncle in the Oncocerida is commonly located at or near the ventral margin. Connecting rings are mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oncocerid
The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian (early Carboniferous; one possible member is known from the Early Permian), in which the connecting rings are thin and siphuncle segments are variably expanded (Flower, 1950). At present the order consists of some 16 families, a few of which, such as the Oncoceratidae, Brevicoceratidae, and Acleistoceratidae contain a fair number of genera each while others like the Trimeroceratidae and Archiacoceratidae are represented by only two or three (Sweet, 1964). Physical characteristics The shells of oncocerids are primarily somewhat compressed cyrtoconic brevicones. More advanced forms include gyrocones, serpenticones, torticones, and elongate orthocones and cyrtocones, reflective of the different families and genera (Flower, 1950; Sweet, 1964). The siphuncle in the Oncocerida is commonly located at or near the ventral margin. Connecting rings are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Museum (Prague)
The National Museum (NM) (Czech: ''Národní muzeum'') is a Czech museum institution intended to systematically establish, prepare, and publicly exhibit natural scientific and historical collections. It was founded in 1818 by Kašpar Maria Šternberg. Historian František Palacký was also strongly involved in the foundation of the museum. The National Museum houses nearly 14 million items from the areas of natural history, history, arts, music and librarianship, which are located in dozens of museum buildings. The main building of the National Museum has been renovated in 2011–2019, and permanent exhibitions are gradually being opened from Spring 2020. Origins After the French Revolution, royal and private collections of art, science and culture were made available to the public. The beginnings of the museum can be seen as far back as 1796 when the private Society of Patriotic Friends of the Arts was founded by Count Casper Sternberk-Manderschied and a group of other prominen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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