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Discosoridae
Discosoridae comprise a family of endogastric discosorids, (Cephalopoda, Nautiloidea), with endocones in the siphuncle, ranging from the Middle Silurian to Middle Devonian. Shell morphology The shell in the Discosoridae is conical, expanding variably with respect to genus. Curvature tends to be slight with the ventral or siphuncular side slightly concave in profile (the endogastric condition), and the opposite dorsal side arched or convex in profile (another endogastric condition). The siphuncle is composed of broadly rounded segments the increase rapidly in size toward the aperture, with growth. Expansion is commonly greater than that of the shell itself, and lies ventral of the center. Septal necks are short, brims long and recumbent. Connecting rings are thin and poorly known. Bullettes at the apical end of the connecting rings, which grasp the periphery of the previous septal foramina and connect to the inside of the previous septal necks, are never swollen. Endocones a ... [...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] |
Discosorus
''Discosorus'', a genus of the Discosorida and member of the family Discosoridae. Not to be confused with ''Discoceras''. ''Discosorus'' consists of rapidly expanding endogastric brevicones, mostly known from isolated siphuncles composed of broadly expanded segments that increase rapidly in size. Septal necks are recumbent, connecting rings thin, bullettes small. The siphuncle interior is occupied by endocones produced by layered annular deposits expanded back toward the apex, leaving a central tube running down the middle. The short phragmocone is poorly known. ''Discosorus'' is found in the Middle Silurian of eastern and arctic North America and as part of the Discosoratidae is derived from the Lowoceratidae which forms a link in the Early Silurian from the Late Ordovician exogastric ''Faberoceras'' of the Westonoceratidae. See also *List of nautiloids References *Discosorus, pK336 in Vol K of the Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Konglungenoceras
''Konglungenoceras'' is a discorid from the lower Silurian of Europe (Norway) included in the Cyrtogomphoceratidae that lacks the septal foramina grasping bullettes at the adapical end of the connecting rings. shells are endogastric and strongly compressed, such that the ventral or siphuncle side is curved inward and the dorso-ventral height is greater than the width. Endosiphuncular deposits in the apical portion of the siphuncle consist of thick overlapping parietal laminae that form endocones, similar to those is ''Discosorus'' and '' Alpenoceras''. Although included in the Cyrtogomphoceratidae, derivation undetermined, siphuncle characters as well as stratigraphic position are suggestive of the Discosoridae Discosoridae comprise a family of endogastric discosorids, (Cephalopoda, Nautiloidea), with endocones in the siphuncle, ranging from the Middle Silurian to Middle Devonian. Shell morphology The shell in the Discosoridae is conical, expanding va .... References *Curt ... [...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] |
Kayoceras
''Kayoceras'' is a genus of middle Silurian nautiloid cephalopods, known from Iowa and Illinois, belonging to the Discosoridae. Related genera include ''Discosorus'', '' Endodiscosorus'', and '' Stokesoceras''. ''Kayoceras'' has a short, breviconic shell, like ''Discosorus'', but with a more central siphuncle. Derivation is probably from ''Discosorus'', through an evolutionary shifting of the siphuncle position, which has its origin in the 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 Ca ..., possibly through '' Tuyloceras''. References * Curt Teichert, 1964. Nautiloidea -Discosorida; Treatise on Invertebrate Paleontology, Part K. Geological Society of America and University of Kansas Press. ''Kayoceras'', Paleobiology database. Prehistoric nautiloid genera Disc ... [...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] |
Devonian Animals
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, where rocks from this period were first studied. The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. The arthropod groups of myriapods, arachnids and hexapods also became well-established early in this period, after starting their expansion to land at least from the Ordovician period. Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fishes. The placoderms began dominating al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silurian Animals
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 durin ... [...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] |
