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Psiloceras
''Psiloceras'' is an extinct genus of ammonite. ''Psiloceras'' is among the earliest known Jurassic ammonites, and the appearance of the earliest ''Psiloceras'' species form the definition for the base of the Jurassic. Unlike most earlier ammonites, which had complex shell shapes and ornamentation, ''Psiloceras'' had a smooth shell. Taxonomy Almost all ammonites, with the sole exemption of a few members of the family Psiloceratidae, including ''Psiloceras'' were wiped out at the Triassic–Jurassic extinction event (201.3 million years ago). Most authors assume that ''Psiloceras'' descended from the Phyllocerataceae. ''P. spelae'' is probably the earliest species of ''Psiloceras''. Biostratigraphic significance The International Commission on Stratigraphy (ICS) has assigned the First Appearance Datum of the ''Psiloceras spela''-group as the defining biological marker for the start of the Hettangian, 201.3 ± 0.2 million years ago, the earliest stage of the Jurassic, with the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blue Lias
The Blue Lias is a formation (stratigraphy), geological formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassic times, between 195 and 200 million years ago. The Blue Lias is famous for its fossils, especially ammonites. Its age corresponds to the Rhaetian to lower Sinemurian stages of the geological timescale, thus fully including the Hettangian stage. It is the lowest of the three divisions of the Lower Jurassic period and, as such, is also given the name ''Lower Lias''. stratigraphy, Stratigraphically it can be subdivided into three Geological unit#Lithostratigraphic units, members: the Wilmcote Limestone, Saltford Shale and Rugby, Warwickshire, Rugby Limestone. Lithology and facies The Blue Lias comprises decimetre scale alternations of clay, argillaceous limestone and mudstone. These alternations are caused by short ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hettangian Life
The Hettangian is the earliest age (geology), age and lowest stage (stratigraphy), stage of the Jurassic Geological time scale, Period of the geologic timescale. It spans the time between 201.3 ± 0.2 annum, Ma and 199.3 ± 0.3 Ma (million years ago). The Hettangian follows the Rhaetian (part of the Triassic Period) and is followed by the Sinemurian. In European stratigraphy the Hettangian is a part of the time span in which the Lias Group, Lias was deposited. An example is the British Blue Lias, which has an upper Rhaetian to Sinemurian age. Another example is the lower Lias from the Northern Limestone Alps where well-preserved but very rare ammonites, including ''Alsatites'', have been found. Stratigraphic definitions The Hettangian was introduced in the literature by Swiss palaeontologist, Eugène Renevier, in 1864. The stage takes its name from Hettange-Grande, a town in north-eastern France, just south of the border with Luxembourg on the main road from Luxembourg City to M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jurassic Ammonites
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. The Jurassic constitutes the second and middle period of the Mesozoic, Mesozoic Era as well as the eighth period of the Phanerozoic, Phanerozoic Eon and is named after the Jura Mountains, where limestone strata from the period were first identified. The start of the Jurassic was marked by the major Triassic–Jurassic extinction event, associated with the eruption of the Central Atlantic magmatic province, Central Atlantic Magmatic Province (CAMP). The beginning of the Toarcian Age started around 183 million years ago and is marked by the Toarcian Oceanic Anoxic Event, a global episode of Anoxic event, oceanic anoxia, ocean acidification, and elevated global temperatures associated with extinctions, likely caused by the eruption of the Kar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hettangian
The Hettangian is the earliest age and lowest stage of the Jurassic Period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma (million years ago). The Hettangian follows the Rhaetian (part of the Triassic Period) and is followed by the Sinemurian. In European stratigraphy the Hettangian is a part of the time span in which the Lias was deposited. An example is the British Blue Lias, which has an upper Rhaetian to Sinemurian age. Another example is the lower Lias from the Northern Limestone Alps where well-preserved but very rare ammonites, including '' Alsatites'', have been found. Stratigraphic definitions The Hettangian was introduced in the literature by Swiss palaeontologist, Eugène Renevier, in 1864. The stage takes its name from Hettange-Grande, a town in north-eastern France, just south of the border with Luxembourg on the main road from Luxembourg City to Metz. The base of the Hettangian Stage (which is also the base of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Psiloceratidae
Psiloceratidae is an extinct family of cephalopods belonging to the ammonite subclass. Description The Psiloceratidae are evolute, smooth or with blunt primary ribbing. The venter is rounded and generally smooth, in some feebly keeled. Sutures are simple with phylloid saddle endings in some. The aptychus is single, found in sutu in Psiloceras Genera * ''Badouxia'' Guex and Taylor, 1976 * ''Caloceras'' * ''Discamphiceras'' * ''Euphyllites'' Wahner, 1898 * ''Franziceras'' Buckman, 1923 * ''Kammerkaroceras'' * ''Laqueoceras'' * ''Murihikuites'' Stevens, 2004 * ''Paradiscamphiceras'' Taylor, 1988 * ''Paraphylloceras'' Salfeld, 1919 * ''Psiloceras'' * ''Psilophyllites'' Distribution Fossils of species within this genus have been found in the Triassic rocks of Canada, in the Jurassic rocks of Argentina, Austria, Canada, China, France, Germany, Hungary, Mexico, New Zealand, Spain), United Kingdom, United States, as well as in the Cretaceous of Australia and Russia. References * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Global Boundary Stratotype Sections And Points
This is a list of Global Boundary Stratotype Sections and Points. Since 1977, Global Boundary Stratotype Sections and Points (abbreviated GSSPs) are internationally agreed upon reference points on stratigraphic sections of rock which define the lower boundaries of stages on the geologic time scale. They are selected by the International Commission on Stratigraphy based on multiple factors, but their accessibility and the degree to which they are representative of the same boundary on sections worldwide are among the most important. Since GSSPs require well-preserved sections of rock without interruptions in sedimentation, and since most are defined by different stages of animal life, defining them becomes progressively more difficult as one goes farther back in time. Organization of this list This list is divided first into the geologic eras of the Phanerozoic (the Cenozoic, the Mesozoic, and the Paleozoic) and then into the geologic periods of each era. Each period is marke ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triassic–Jurassic Extinction Event
The Triassic–Jurassic (Tr-J) extinction event (TJME), often called the end-Triassic extinction, marks the boundary between the Triassic and Jurassic periods, . It represents one of five major extinction events during the Phanerozoic, profoundly affecting life on land and in the oceans. In the seas, about 23–34% of marine genus, genera disappeared; Coral, corals, Bivalvia, bivalves, Brachiopod, brachiopods, Bryozoa, bryozoans, and Radiolaria, radiolarians suffered severe losses of diversity and Conodont, conodonts were completely wiped out, while marine vertebrates, Gastropoda, gastropods, and benthic foraminifera were relatively unaffected. On land, all Archosauromorpha, archosauromorph reptiles other than Crocodylomorpha, crocodylomorphs, dinosaurs, and pterosaurs became extinct. Crocodylomorphs, dinosaurs, pterosaurs, and mammals were left largely untouched, allowing them to become the dominant land animals for the next 135 million years. Plants were likewise significantly a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Commission On Stratigraphy
The International Commission on Stratigraphy (ICS), sometimes unofficially referred to as the International Stratigraphic Commission, is a daughter or major subcommittee grade scientific organization that concerns itself with stratigraphy, stratigraphical, geology, geological, and chronology, geochronological matters, worldwide. It is the largest subordinate body of the International Union of Geological Sciences (IUGS). The ICS is essentially a permanent working committee, working subcommittee, which meets far more regularly than the quadrennial meetings scheduled by the IUGS, when it meets as a congress or committee, membership of the whole. Aims One of its main aims, a project begun in 1974, is to establish a multidisciplinary standard and global geologic time scale that will ease paleontology, paleontological and geobiology, geobiological comparisons region to region by benchmarks with stringent and rigorous strata criteria called Global Boundary Stratotype Section and Points ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
First Appearance Datum
First appearance datum (FAD) is a term used by geologists and paleontologists to designate the first appearance of a species in the geologic record. FADs are determined by identifying the geologically oldest fossil discovered, to date, of a particular species. A related term is last appearance datum (LAD), the last appearance of a species in the geologic record. FADs are frequently used to designate segments in the geologic time scale. A given FAD can be used to define a Global Boundary Stratotype Section and Point (GSSP). For example, the beginning of the Tremadocian Stage of the Ordovician Period is marked by the first appearance of the conodont ''Iapetognathus fluctivagus'' in the geologic record. This occurs in bed 23 of the rock formation known as the Green Point section, located in western Newfoundland, as well as in geologically correlated strata in many parts of the world. However, diachronous FADs can be problematic for correlating chronostratigraphic units, particular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type (biology)
In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to anchor or centralizes the defining features of that particular taxon. In older usage (pre-1900 in botany), a type was a taxon rather than a specimen. A taxon is a scientifically named grouping of organisms with other like organisms, a set that includes some organisms and excludes others, based on a detailed published description (for example a species description) and on the provision of type material, which is usually available to scientists for examination in a major museum research collection, or similar institution. Type specimen According to a precise set of rules laid down in the International Code of Zoological Nomenclature (ICZN) and the ''International Code of Nomenclature for algae, fungi, and plants'' (ICN), the scientific name of every taxon is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
