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Gnathifera (phylum)
Gnathifera (from the Greek '' gnáthos'', “jaw”, and the Latin '' -fera'', “bearing”) is a clade of generally small spiralians characterized by complex jaws made of chitin. It comprises the phyla Gnathostomulida, Rotifera, Micrognathozoa, and Chaetognatha. It may also include the Cycliophora. Gnathiferans include some of the most abundant phyla. Rotifers are among the most diverse and abundant freshwater animals and chaetognaths are among the most abundant marine plankton. Description The most distinctive characteristic of gnathiferans is the presence of complex sclerotized mouthparts made of chitin. In most gnathiferans, the anus opens on the dorsal surface of the animal. In micrognathozoans and gnathostomulids, the anus is transient and only forms during defecation. Unlike other gnathiferans, in chaetognaths and ''Amiskwia'' the anus is located on the ventral surface in a subterminal position. Development All known gnathiferans are direct developers. Though gnathif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fortunian
The Fortunian age marks the beginning of the Phanerozoic Eon, the Paleozoic Era, and the Cambrian Period. It is the first of the two stages of the Terreneuvian series. Its base is defined as the first appearance of the trace fossil ''Treptichnus pedum'' million years ago. The top of the Fortunian which is the base of the Stage 2 of the Cambrian has not been formally defined yet, but will correspond to the appearance of an Archeocyatha species or "Small shelly fossils" approximately million years ago. The name Fortunian is derived from a part of the Burin Peninsula, the town of Fortune near the GSSP and Fortune Bay. GSSP The type locality (GSSP) of the Fortunian stage is in Fortune Head, at the northern edge of the Burin Peninsula, Newfoundland, Canada (). This GSSP coincides with the base of the Terreneuvian series, the Precambrian-Cambrian boundary and the beginning of the Phanerozoic. The outcrops show a carbonate-siliciclastic succession which is mapped as the Chapel Island F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seisonida
Seisonidae is a family of rotifers, found on the gills of ''Nebalia'', a marine crustacean. Peculiar among rotifers, males and females are both present and equal in size. Males and females are similar with paired gonads. It is considered to have diverged from the other rotifers early on, and in one treatment is placed in a separate class Seisonoidea. They have a large and elongate body with reduced corona. Their muscular system is similar to that of other rotifers: they have longitudinal muscles as well as open annular muscles. Species Two genera with total three species belong to Seisonidae: * '' Paraseison'' Plate, 1887 ** '' Paraseison annulatus'' (Claus, 1876) — ectoparasite of ''Nebalia'' * '' Seison'' Grube, 1861 ** '' Seison nebaliae'' Grube, 1861 – commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protoconodont
Protoconodonts are an extinct taxonomic group of conodonts or, possibly, Chaetognaths. Chaetognaths (also known as arrow worms) were thought possibly to be related to some of the animals grouped with the conodonts. The conodonts themselves, however, are thought to be related to the vertebrates. It is now thought that protoconodont elements (e.g., ''Protohertzina ''Protohertzina'' is a genus of conodonts ( protoconodonts or paraconodonts) or, possibly, Chaetognaths, found at the beginning of the Cambrian explosion. Protoconodonts are an extinct taxonomic group of conodonts.Zooproblematica and mollusca ... anabarica'' Missarzhevsky, 1973), are probably grasping spines of chaetognaths rather than the oropharyngeal elements of conodonts. Previously chaetognaths in the Early Cambrian were only suspected from these protoconodont elements (for example '' Phakelodus''), but the more recent discoveries of body fossils have confirmed their presence then. References * Middle and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ''zōḗ'' (), "life", meaning "ancient life" ). It is the longest of the Phanerozoic eras, lasting from , and is subdivided into six geologic periods (from oldest to youngest): # Cambrian # Ordovician # Silurian # Devonian # Carboniferous # Permian The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon and is followed by the Mesozoic Era. The Paleozoic was a time of dramatic geological, climatic, and evolutionary change. The Cambrian witnessed the most rapid and widespread diversification of life in Earth's history, known as the Cambrian explosion, in which most modern phyla first appeared. Arthropods, molluscs, fish, amphibians, reptiles, and synapsids all evolved during the Paleozoic. Life began in the ocean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1. It is considered by some to be an interglacial period within the Pleistocene Epoch, called the Flandrian interglacial.Oxford University Press – Why Geography Matters: More Than Ever (book) – "Holocene Humanity" section https://books.google.com/books?id=7P0_sWIcBNsC The Holocene corresponds with the rapid proliferation, growth and impacts of the human species worldwide, including all of its written history, technological revolutions, development of major civilizations, and overall significant transition towards urban living in the present. The human impact on modern-era Earth and its ecosystems may be considered of global si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "dawn") and (''kainós'', "new") and refers to the "dawn" of modern ('new') fauna that appeared during the epoch. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope Carbon-13, 13C in the atmosphere was exceptionally low in comparison with the more common isotope Carbon-12, 12C. The end is set at a major extinction event called the ''Grande Coupure'' (the "Great Break" in continuity) or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Popigai impact structure, Siberia and in what is now ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dominican Amber
Dominican amber is amber from the Dominican Republic derived from resin of the extinct tree ''Hymenaea protera''. Dominican amber differentiates itself from Baltic amber by being nearly always transparent, and it has a higher number of fossil inclusions. This has enabled the detailed reconstruction of the ecosystem of a long-vanished tropical forest.George Poinar, Jr. and Roberta Poinar, 1999. ''The Amber Forest: A Reconstruction of a Vanished World'', (Princeton University Press) Age A study in the early 1990s returned a date up to 40 million years old. However, according to Poinar, Dominican amber dates from Oligocene to Miocene, thus about 25 million years old. The oldest, and hardest of this amber comes from the mountain region north of Santiago. The ''La Cumbre'', ''La Toca'', ''Palo Quemado'', ''La Bucara'', and ''Los Cacaos'' mining sites in the ''Cordillera Septentrional'' not far from Santiago. Amber has also been found in the south-eastern Bayaguana/Sabana de la Mar a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Entoprocta
Entoprocta (), or Kamptozoa , is a phylum of mostly sessile aquatic animals, ranging from long. Mature individuals are goblet-shaped, on relatively long stalks. They have a "crown" of solid tentacles whose cilia generate water currents that draw food particles towards the mouth, and both the mouth and anus lie inside the "crown". The superficially similar Bryozoa (Ectoprocta) have the anus outside a "crown" of hollow tentacles. Most families of entoprocts are colonial, and all but 2 of the 150 species are marine. A few solitary species can move slowly. Some species eject unfertilized ova into the water, while others keep their ova in brood chambers until they hatch, and some of these species use placenta-like organs to nourish the developing eggs. After hatching, the larvae swim for a short time and then settle on a surface. There they metamorphose, and the larval gut rotates by up to 180°, so that the mouth and anus face upwards. Both colonial and solitary species also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyphyly
A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. 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 more with ecology than with system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aschelminth
The Aschelminthes (also known as Aeschelminthes, Nemathelminthes, Nematodes), closely associated with the Platyhelminthes, are an obsolete phylum of pseudocoelomate and other similar animals that are no longer considered closely related and have been promoted to phyla in their own right. The term Aschelminth is now generally only used as an informal name for any member of the approximately ten different invertebrate phyla formerly included within Aschelminthes. It is a polyphyletic group. Subdivisions Although invertebrate experts do not necessarily agree on these categorizations, groups that are generally incorporated into Aschelminthes include: * Acanthocephala * Chaetognatha * Cycliophora * Gastrotricha * Kinorhyncha * Loricifera * Nematoda * Nematomorpha * Priapulida * Rotifera In addition, Entoprocta and Tardigrada Tardigrades (), known colloquially as water bears or moss piglets, are a phylum of eight-legged segmented micro-animals. They were first described by the G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spiralia
The Spiralia are a morphologically diverse clade of protostome animals, including within their number the molluscs, annelids, platyhelminths and other taxa. The term ''Spiralia'' is applied to those phyla that exhibit canonical spiral cleavage, a pattern of early development found in most (but not all) members of the Lophotrochozoa. Distribution of spiralian development across phylogeny Members of the molluscs, annelids, platyhelminths and nemerteans have all been shown to exhibit spiral cleavage in its classical form. Other spiralian phyla (rotifers, brachiopods, phoronids, gastrotrichs, and bryozoans) are also said to display a derived form of spiral cleavage in at least a portion of their constituent species, although evidence for this is sparse. Lophotrochozoa within Spiralia Previously, spiral cleavage was thought to be unique to the Spiralia in the strictest sense—animals such as molluscs and annelids which exhibit classical spiral cleavage. The presence of spiral cleav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
