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Silurian Eurypterids
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] |
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] |
Ordovician–Silurian Extinction Events
The Late Ordovician mass extinction (LOME), sometimes known as the end-Ordovician mass extinction or the Ordovician–Silurian extinction, is the first of the "big five" major mass Extinction event, extinction events in Earth's history, occurring roughly 445 million years ago (Ma). It is often considered to be the second-largest-known extinction event just behind the end-Permian mass extinction, in terms of the percentage of Genus, genera that became extinct. Extinction was global during this interval, eliminating 49–60% of marine genera and nearly 85% of marine species. Under most tabulations, only the Permian–Triassic mass extinction exceeds the Late Ordovician mass extinction in biodiversity loss. The extinction event abruptly affected all major taxonomic groups and caused the disappearance of one third of all brachiopod and bryozoan families, as well as numerous groups of conodonts, trilobites, echinoderms, corals, bivalves and graptolites. Despite its taxonomic severity, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osteichthyan
Osteichthyes ( ; ), also known as osteichthyans or commonly referred to as the bony fish, is a Biodiversity, diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes (cartilaginous fish) and the extinct placoderms and acanthodians, which have endoskeletons primarily composed of cartilage. The vast majority of extant taxon, extant fish are members of Osteichthyes, being an extremely diverse and abundant group consisting of 45 order (biology), orders, over 435 family (biology), families and 28,000 species. The group is divided into two main clades, the ray-finned fish (Actinopterygii, which makes up the vast majority of extant fish) and the lobe-finned fish (Sarcopterygii, which gave rise to all land vertebrates, i.e. tetrapods). The oldest known fossils of bony fish are about 425 million years old from the late Silurian, which are also transitional fossils showing a dentition, tooth pattern th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cartilaginous Fish
Chondrichthyes (; ) is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fish'', which have skeletons primarily composed of bone tissue. Chondrichthyes are aquatic vertebrates with paired fins, paired nares, placoid scales, conus arteriosus in the heart, and a lack of opercula and swim bladders. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates. The class is divided into two subclasses: Elasmobranchii (sharks, rays, skates and sawfish) and Holocephali ( chimaeras, sometimes called ghost sharks, which are sometimes separated into their own class). Extant chondrichthyans range in size from the finless sleeper ray to the over whale shark. Anatomy Skeleton The skeleton is cartilaginous. The notochord is gradually replaced by a vertebral column during development, e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acanthodian
Acanthodii or acanthodians is an extinct class of Gnathostomata, gnathostomes (jawed fishes). They are currently considered to represent a paraphyletic Evolutionary grade, grade of various fish lineages Basal (phylogenetics), basal to extant taxon, extant Chondrichthyes, which includes living sharks, Batoidea, rays, and chimaeras. Acanthodians possess a mosaic of features shared with both Osteichthyes, osteichthyans (bony fish) and chondrichthyans (cartilaginous fish). In general body shape, they were similar to modern sharks, but their Epidermis (skin), epidermis was covered with tiny rhomboid platelets like the scales of holosteians (gars, bowfins). The popular name "spiny sharks" is because they were superficially shark-shaped, with a streamlined body, paired Fish fin, fins, a strongly upturned tail, and stout, largely immovable bony spines supporting all the fins except the tail—hence, "spiny sharks". However, acanthodians are not true sharks; their close relation to modern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Placoderm
Placoderms (from Ancient Greek πλάξ [''plax'', ''plakos''] 'Plate (animal anatomy), plate' and δέρμα [''derma''] 'skin') are vertebrate animals of the class (biology), class Placodermi, an extinct group of prehistoric fish known from Paleozoic fossils during the Silurian and the Devonian geological period, periods. While their endoskeletons are mainly cartilaginous, their head and thorax were covered by articulated armour (zoology), armoured plates (hence the name), and the rest of the body was scale (zoology), scaled or naked depending on the species. Placoderms were among the first jawed fish (their fish jaw, jaws likely Evolution, evolved from the first pair of gill arches), as well as the first vertebrates to have true tooth, teeth. They were also the first fish clade to develop pelvic fins, the second set of paired fins and the homology (biology), homologous precursor to hindlimbs in tetrapods. 380-million-year-old fossils of three other genera, ''Incisoscutum'', ''M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnathostomata
Gnathostomata (; from Ancient Greek: (') 'jaw' + (') 'mouth') are jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all extant vertebrates, including all living bony fishes (both ray-finned and lobe-finned, including their terrestrial tetrapod relatives) and cartilaginous fishes, as well as extinct prehistoric fish such as placoderms and acanthodians. Most gnathostomes have retained ancestral traits like true teeth, a stomach, and paired appendages ( pectoral and pelvic fins, limbs, wings, etc.). Other traits are elastin, horizontal semicircular canal of the inner ear, myelinated neurons, and an adaptive immune system which has discrete secondary lymphoid organs (spleen and thymus) and uses V(D)J recombination to create antigen recognition sites, rather than using genetic recombination in the variable lymphocyte receptor gene. It is now assumed that Gnathostomata evolved from ancestors that already possessed two pairs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexapoda
The subphylum Hexapoda (from Greek for 'six legs') or hexapods comprises the largest clade of arthropods and includes most of the extant arthropod species. It includes the crown group class Insecta (true insects), as well as the much smaller clade Entognatha, which includes three classes of wingless arthropods that were once considered insects: Collembola (springtails), Protura (coneheads) and Diplura (two-pronged bristletails). The insects and springtails are very abundant and are some of the most important pollinators, basal consumers, scavengers/ detritivores and micropredators in terrestrial environments. Hexapods are named for their most distinctive feature: a three-part body plan with a consolidated thorax and three pairs of legs. Most other arthropods have more than three pairs of legs. Most recent studies have recovered Hexapoda as a subgroup of Pancrustacea. Morphology Hexapods have bodies ranging in length from 0.5 mm to over 300 mm which are divided ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arachnids
Arachnids are arthropods in the class Arachnida () of the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaroons. Adult arachnids have eight legs attached to the cephalothorax. In some species the frontmost pair of legs has converted to a sensory function, while in others, different appendages can grow large enough to take on the appearance of extra pairs of legs. Almost all extant arachnids are terrestrial, living mainly on land. However, some inhabit freshwater environments and, with the exception of the pelagic zone, marine environments as well. They comprise over 110,000 named species, of which 51,000 are species of spiders. The term is derived from the Greek word (''aráchnē'', 'spider'), from the myth of the hubristic human weaver Arachne, who was turned into a spider. Morphology Almost all adult arachnids have eight legs, unlike adult insects whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myriapods
Myriapods () are the members of subphylum Myriapoda, containing arthropods such as millipedes and centipedes. The group contains about 13,000 species, all of them terrestrial. Although molecular evidence and similar fossils suggests a diversification in the Cambrian Period, the oldest known fossil record of myriapods dates between the Late Silurian and Early Devonian, with '' Pneumodesmus'' preserving the earliest known evidence of air-breathing on land. Other early myriapod fossil species around the similar time period include '' Kampecaris obanensis'' and '' Archidesmus'' sp. The phylogenetic classification of myriapods is still debated. The scientific study of myriapods is myriapodology, and those who study myriapods are myriapodologists. Anatomy Myriapods have a single pair of antennae and, in most cases, simple eyes. Exceptions are the two classes of symphylans and pauropods, the millipede order Polydesmida and the centipede order Geophilomorpha, which are all ey ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nature Communications
''Nature Communications'' is a peer-reviewed, open access, scientific journal published by Nature Portfolio since 2010. It is a multidisciplinary journal that covers the natural sciences, including physics, chemistry, earth sciences, medicine, and biology. The journal has editorial offices in London, Berlin, New York City, and Shanghai. The founding editor-in-chief was Lesley Anson, followed by Joerg Heber, Magdalena Skipper, and Elisa De Ranieri. the editors are Nathalie Le Bot for health and clinical sciences, Stephane Larochelle for biological sciences, Enda Bergin for chemistry and biotechnology, and Prabhjot Saini for physics and earth sciences. Starting October 2014, the journal only accepted submissions from authors willing to pay an article processing charge. Until the end of 2015, part of the published submissions were only available to subscribers. In January 2016, all content became freely accessible. Starting from 2017, the journal offers a deposition ser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glomeromycota
Glomeromycota (often referred to as glomeromycetes, as they include only one class, Glomeromycetes) are one of eight currently recognized division (mycology), divisions within the Kingdom (biology), kingdom Fungi, with approximately 230 described species. Members of the Glomeromycota form arbuscular mycorrhizas (AMs) with the thalli of bryophytes and the roots of vascular plant, vascular land plants. Not all species have been shown to form AMs, and one, ''Geosiphon pyriformis'', is known not to do so. Instead, it forms an endocytobiotic association with ''Nostoc'' cyanobacterium, cyanobacteria. The majority of evidence shows that the Glomeromycota are dependent on land plants (''Nostoc'' in the case of ''Geosiphon'') for carbon and energy, but there is recent circumstantial evidence that some species may be able to lead an independent existence. The arbuscular mycorrhizal species are terrestrial and widely distributed in soils worldwide where they form symbioses with the roots of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
