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Bickmorites
''Bickmorites'' is an extinct nautiloid cephalopod genus known from the upper Ordovician to the middle Silurian of North America and northern Europe (Norway). ''Bickmorites'' has a gyroconic shell, coiled such that whorls are not in contact, although close. The surface is strongly ribbed; ribs slant dorso-ventrally toward the apex. The siphuncle is narrow, located slightly ventral of the center. Septal necks are straight, making the siphuncle orthochoanitic. ''Bickmorites'' seems to bridge the temporal gap between the Upper Ordovivian barrandeoceratid '' Antiplectoceras'' and the Middle Silurian barrandoeceratids ''Gasconsoceras'', ''Laureloceras'', and ''Savageoceras''. See also * List of nautiloids This list of nautiloids is a comprehensive listing of all genera that have ever been included in the subclass Nautiloidea, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered in ... References * Walter C. S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Nautiloids
This list of nautiloids is a comprehensive listing of all genera that have ever been included in the subclass Nautiloidea, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (''nomina dubia''), or were not formally published (''nomina nuda''), as well as junior synonyms of more established names, and genera that are no longer considered nautiloids. Most of the listed genera are found in Part K of the ''Treatise on Invertebrate Paleontology''. Some, added since the year of publication (1964) are found simply in various scientific journals and special publications. The named genera are based on type specimens which are housed in various museums and other academic institutions worldwide, available to interested researchers. Note that ''Allonautilus'' and ''Nautilus'' are the only extant genera. A *†'' Acanthonautilus'' *†'' Acaroceras'' *†''Acleistoceras'' *†'' Acrosphaerorthoceras'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic 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 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 beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed 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 Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier C ... [...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 d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nautiloid
Nautiloids are a group of marine cephalopods ( Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and '' Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded species. They flourished during the early Paleozoic era, when they constituted the main predatory animals. Early in their evolution, nautiloids developed an extraordinary diversity of shell shapes, including coiled morphologies and giant straight-shelled forms (orthocones). Only a handful of rare coiled species, the nautiluses, survive to the present day. In a broad sense, "nautiloid" refers to a major cephalopod subclass or collection of subclasses (Nautiloidea ''sensu lato''). Nautiloids are typically considered one of three main groups of cephalopods, along with the extinct ammonoids (ammonites) and living coleoids (such as squid, octopus, and kin). While ammonoids and coleoids are monophyletic clades with exclusive ancestor-descendan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cephalopod
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 i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gasconsoceras
''Gasconsoceras'' is a genus of nautiloid cephalopods belonging to the tarphyceroid family Barrandeoceratidae, known from Middle Silurian marine strata in 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 .... Shells of ''Gasconsoceras'' are rapidly enlarging gyrocones and serpenticones covered by fine transverse and longitudinal striae and prominent dorsal and lateral transverse ribs. A fair degree of mobility is indicated by the deep hyponomic sinus. Other than being between center and venter, the siphuncle is poorly known. References Prehistoric nautiloid genera Silurian cephalopods {{paleo-nautiloidea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laureloceras
''Laureloceras'' is a genus of the tarphycerid family Plectoceratidae that lived during the Middle Silurian in what is now North America. The shell of ''Laureloceras'' is a smooth, slender, compressed cyrtocone or gyrocone with the venter more narrowly rounded than the dorsum. Sutures are transverse but may form broad lateral lobes. The siphuncle is subventral - close to the outer rim; necks are straight, connecting rings slightly expanded into the chambers. Cameral and siphonal deposits are lacking. ''Laureloceras'' was previously included in the Barrandeoceratidae (Flower, 1950, Sweet, 1964) but was removed (Flower, 1984) primarily on the bases of the subventral siphuncle (Barrandeoceratid siphuncles are central - subcentral. Reassignment to the Tarphycerida from the Barrandeocerida is based on barrandeoceratid taxa being polyphyletic (having more than one common ancestor). Barrandeocerina The Barrandeocerina comprise a suborder of Early Paleozoic nautiloid cephalopods, primi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Savageoceras
The genus ''Savageoceras'' is a barrandeoceratid first known from the Middle Silurian of Illinois consisting of rapidly enlarging, depressed cyrtocones with a trapezoidal section; ventral side wider and flatter than dorsal; sides converging on dorsum. Sutures have slight lateral and ventral lobes and ventrolateral saddles. The surface is covered by transverse striae and has rib-like rings that are more prominent at the ventrolateral shoulders but otherwise vaguely defined. The siphuncle is central; interior unknown. References * Sweet, W.C. Nautiloidea - Barrandeocerida. ''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 Soc. of America and Univ. of Kansas press. {{Taxonbar, from=Q7427790 Prehistoric nautiloid gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prehistoric Nautiloid Genera
Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use of symbols, marks, and images appears very early among humans, but the earliest known writing systems appeared 5000 years ago. It took thousands of years for writing systems to be widely adopted, with writing spreading to almost all cultures by the 19th century. The end of prehistory therefore came at very different times in different places, and the term is less often used in discussing societies where prehistory ended relatively recently. In the early Bronze Age, Sumer in Mesopotamia, the Indus Valley Civilisation, and ancient Egypt were the first civilizations to develop their own scripts and to keep historical records, with their neighbors following. Most other civilizations reached the end of prehistory during the following Iron Age. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Ordovician First Appearances
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Silurian Extinctions
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 t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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