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Fusulinida
The Fusulinida is an extinct order within the Foraminifera in which the tests are traditionally considered to have been composed of microgranular calcite. Like all forams, they were single-celled organisms. In advanced forms the test wall was differentiated into two or more layers. Loeblich and Tappan, 1988, gives a range from the Lower Silurian to the Upper Permian, with the fusulinid foraminifera going extinct with the Permian–Triassic extinction event. While the latter is true, a more supported projected timespan is from the Mid-Carboniferous period. Taxonomy Thirteen superfamilies are presently recognised, based on taxa (families) included in the three superfamilies given in the Treatise. Three are based on families in the Parathuramminacea, 1964, and nine families in the Endothyracea, 1964. The Fusulinacea remains the same in both sources (Treatise 1964 and Loeblich and Tappan, 1988). The term fusulinata has traditionally been used to refer to all palaeozoic forami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microgranular
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Globothalamea
Globothalamea comprises a class of multichambered foraminifera based in part on SSU rDNA evidence; the other is Tubothalamea. Six orders are included, which vary notably in composition, wall structure, and chamber arrangement. The Lituolida, Loftusiida, and Textulariida (as emended) have tests (shells) of agglutinated matter, glued together by various cements, but differ in chamber arrangement, wall structure, and complexity. In contrast the Carterinida, Robertinida and Rotaliida, with buliminids lumped into the Rotaliida, have calcareous tests. Those of rotaliid genera, which vary considerably, are of perforate hyaline (glassy) calcite. in contrast the Carterinida have tests composed of bundled calcite spicules. The Robertida differ in being composed, instead, of aragonite. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotaliida
The Rotaliida are an order of Foraminifera, characterized by multilocular tests (shells) composed of bilamellar perforate hyaline lamellar calcite that may be optically radial or granular. In form, rotaliid tests are typically enrolled, but may be reduced to biserial or uniserial, or may be encrusting with proliferated chambers. Chambers may be simple or subdivided by secondary partitions; the surface is smooth, papillate, costate, striate, or cancellate; the aperture is simple or with an internal toothplate, entosolenian tube, or hemicylindrical structure; it may have an internal canal or stolen systems. Rotaliids are primarily oceanic benthos, although some are common in shallower estuarine waters. They also include many important fossils, such as the nummulitids. Taxonomy The Rotaliida are now divided into the following superfamilies: [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scanning Electron Microscope
A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface topography and composition. The electron beam is scanned in a raster scan pattern, and the position of the beam is combined with the intensity of the detected signal to produce an image. In the most common SEM mode, secondary electrons emitted by atoms excited by the electron beam are detected using a secondary electron detector ( Everhart–Thornley detector). The number of secondary electrons that can be detected, and thus the signal intensity, depends, among other things, on specimen topography. Some SEMs can achieve resolutions better than 1 nanometer. Specimens are observed in high vacuum in a conventional SEM, or in low vacuum or wet conditions in a variable pressure or environmental SEM, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyphyly
A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of convergent evolution. The arrangement of the members of a polyphyletic group is called a polyphyly .. ource for pronunciation./ref> It is contrasted with monophyly and paraphyly. For example, the biological characteristic of warm-bloodedness evolved separately in the ancestors of mammals and the ancestors of birds; "warm-blooded animals" is therefore a polyphyletic grouping. Other examples of polyphyletic groups are algae, C4 photosynthetic plants, and edentates. Many taxonomists aim to avoid homoplasies in grouping taxa together, with a goal to identify and eliminate groups that are found to be polyphyletic. This is often the stimulus for major revisions of the classification schemes. Researchers concerned m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permian–Triassic Extinction Event
The Permian–Triassic extinction event (also known as the P–T extinction event, the Late Permian extinction event, the Latest Permian extinction event, the End-Permian extinction event, and colloquially as the Great Dying,) was an extinction event that occurred approximately 251.9 Million years ago, million years ago (mya), at the boundary between the Permian and Triassic geologic periods, and with them the Paleozoic and Mesozoic eras. It is Earth's most severe known extinction event, with the extinction of 57% of Family (biology), biological families, 62% of genera and 81% of marine biology, marine species, (previous estimates of 90–96% marine species extinction were due to historical conflation with the End-Capitanian mass extinction event, end-Capitanian mass extinction which occurred 7–10 million years earlier) and 70% of terrestrial vertebrate species. It is also the greatest known mass extinction of insects. It is the greatest of the "Big Five" mass extinctions of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Upper Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the sixth and last period of the Paleozoic Era; the following Triassic Period belongs to the Mesozoic Era. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the region of Perm in Russia. The Permian witnessed the diversification of the two groups of amniotes, the synapsids and the sauropsids (reptiles). The world at the time was dominated by the supercontinent Pangaea, which had formed due to the collision of Euramerica and Gondwana during the Carboniferous. Pangaea was surrounded by the superocean Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior. Amniotes, which could better cope with these drier conditions, rose to dominance in place of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lower Silurian
The Silurian ( ) is a geologic period and system spanning 23.5 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 third and shortest period of the Paleozoic Era, and the third of twelve periods of the Phanerozoic Eon. 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 full ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
