|
Blakeoceras
''Blakeoceras'' is a nautiloid cephalopod from the Oncocerida family Nothoceratidae with a curved shell that lived in shallow seas from the Silurian to the Middle Devonian in what has become Europe. The shell of ''Blakeoceras'' is moderately curved (cyrtoconic) with the ventral side on the outer curvature (exogastric) Chambers in the phragmocone are short and wide, separated by straight, close spaced septa. Body chamber short. Siphuncle ventro-marginal, with internal, radial actinosiphonate deposits and concave segments. ''Blakeocers'' is similar to ''Perimecoceras'' in general form but is more broadly expanded and has a proportionally shorter body chamber. '' Conostichoceras'' is less strongly curved and widens more laterally. '' Turnoceras'' is more strongly curved and has a much greater expansion. ''Conostichoceras'' and ''Turnoceras'' are also more breviconic (shorter). ''Blakeoceras'' is an early nothoceratid possibly derived from ''Perimecoceras'' which has its or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perimecoceras
''Perimecoceras'' is a genus of nothoceratids, nautilitoids in the order Oncocerida, with a slowly expanding, compressed, cyrtoconic shell, known from the Upper Silurian of central Europe. ''Perimecoceras'' is similar in general form to the oncoceratid genus '' Oonoceras'' from which it may have been derived, but differs in having a longer body chamber in proportion and in having concave segments to its siphuncle. It as also the most likely ancestral nothoceratid, probably giving rise to '' Blakeoceras'' and other Nothoceratidae. ''Perimecoceras'' probably lived on the sea floor, body chamber horizontal, phragmocone behind arched upward away from the bottom, using a combination of crawling and jet-swimming as it moved about. References * Sweet, W.C. 1964; Nautiloidea -Oncocerida; 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nothoceratidae
Nothoceratidae is a family of nautiloid cephalopods in the orthoceratoid order Oncocerida in which shells are exogastrically or endogastrically breviconic, planospiral, or torticonic; often with a constricted or visored aperture; and a siphuncle commonly composed of concave segments and occupied by actinosiphonate deposits. Some ten genera have been described which lived during the time between the Early Silurian and Late Devonian. The ancestral form is probably '' Perimecoceras'' which is known from the Upper Silurian of central Europe and which is similar in external form the ''Oonoceras'' from the Oncoceratidae. Genera *'' Blakeoceras'' *'' Bolloceras'' *'' Conostichoceras'' *'' Cyrthoceratites'' *'' Lorieroceras'' *'' Metaphragmoceras'' *'' Mutoblakeoceras'' *'' Nothoceras'' *'' Paraconradoceras'' *'' Perimecoceras'' *'' Tafilaltoceras'' *'' Turnoceras'' References * Sweet, W. C. 1964; Nautiloidea -Oncocerida; Treatise on Invertebrate Paleontology The ''Treatise ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conostichoceras
''Conostichoceras'' is a genus of exogastric, breviconic oncocerids included in the family Nothoceratidae, known from the Middle Devonian of central Europe and Upper Devonian of Australia.Sweet, W.C. 1964. Nautiloidea-Oncocerida Treatise on Invertebrate Paleontology part K. It probably lived on and swum above the sea floor. Morphology ''Conostichoceras'', named by Foeste, 1926, produced a depressed exogastric breviconic shell with short, wide chambers and large living chamber, similar to ''Blakeoceras'' and '' Turnoceras'' but differing details especially of the siphuncle. The siphuncle is ventral; nummuloidal in the adapical half of the phragmocone but with concave profiles in the adoral half, and is actinosiphonate. The sides of the living chamber in the adult converge slightly on the aperture. Taxonomy In its broader taxonomy ''Conostichoceras'' belongs to a group of nautiloid cephalopods known as the Nautilitoidea, a superorder that includes the orders Oncocerida, Tarphy ... [...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] |
Middle Devonian Genus Extinctions
Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (other) * Middle Brook (other) * Middle Creek (other) * Middle Island (other) * Middle Lake (other) * Middle Mountain, California * Middle Peninsula, Chesapeake Bay, Virginia * Middle Range, a former name of the Xueshan Range on Taiwan Island * Middle River (other) * Middle Rocks, two rocks at the eastern opening of the Straits of Singapore * Middle Sound, a bay in North Carolina * Middle Township (other) * Middle East Music * "Middle" (song), 2015 * "The Middle" (Jimmy Eat World song), 2001 * "The Middle" (Zedd, Maren Morris and Grey song), 2018 *"Middle", a song by Rocket from the Crypt from their 1995 album ''Scream, Dracula, Scream!'' *"The Middle", a song by Demi Lovato from their debut album ''Don't Forget'' *"The Middle", a song by ... [...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] |
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] |
Oncoceratidae
Oncoceratidae is a family of nauatiloid cephalopods in the order Oncocerida established by Hyatt, 1884, that range from the Middle Ordovician to the Upper Silurian. Diagnosis Oncoceratidae are characterized by generally compressed, cyrtoconic, and breviconic shells with an exogastric curvature such that the ventral profile is convex or more so than dorsal, and in which the siphuncle is generally empty and located ventral of the center. In primitive forms, the siphuncle in early growth stages is composed of tubular segments with almost straight suborthochoanitic septal necks, but becomes cyrtochoanitic with expanded segments in the later growth stages, and is expanded and cyrtochoanitic throughout in advanced forms. In a few advanced forms, the siphuncle is actinosiphonate. (Flower 1950, Sweet 1964) Evolution The Oncoceratidae first appeared early in the Middle Ordovician (Sweet 1964) simultaneously with the Graciloceratidae, Tripteroceratidae, and Valcouroceratidae, deri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turnoceras
''Turnoceras'' is a genus of Devonian cephalopods belonging to the oncocerid family Nothoceratidae. Its shell is broadly expanding and exogastrically curved such that the flattened dorsum is on longitudinally concave side. Aperture unconstricted with no hyponomic sinus for the water jet funnel. siphuncle along the outer, ventral, side, with radial, plate-like actinosiphonate deposits occupying the interior. ''Conostichoceras'' is similar externally, but has a siphuncle with a trapezoidal aspect to its siphuncle segments. ''Perimecoceras'' has similar concave siphuncle segments but is tubular in form. References * Sweet, W.C. 1964; Nautiloidea -Oncocerida; 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 ; Geological Society of A ... [...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] |
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, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phragmocone
The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae. In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a siphuncle which determines buoyancy by means of gas exchange. Despite this benefit, such a large shell adds to the mass of the animal, and hence is disadvantageous in catching fast-moving prey. Some nautiloids, such as the Silurian Ascocerida, dropped the phragmocone upon maturity, presumably to increase speed and maneuverability. They thus became the early Paleozoic equivalent of coleoids. The early coleoids and belemnoids adopted a different approach: the phragmocone was retained but became internal and reduced. In general the shell in cephalopods tends to be vestigial or absent. Fossil record Being the only biomineralised part of most cephalopods, the phragmocone is typically the only part to enter the fossil record. It is somet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
