|
Planaterga
Planaterga is a clade of prosomapod euchelicerates including several synziphosurid genera (mainly bunodids and pseudoniscids) and the group Dekatriata (which in turn includes arachnids, chasmataspidids and eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 Myr, million yea ...s). Planaterga is defined by the opisthosoma with tergites broadest at third or fourth and lacking enlarged axial nodes, carapace (prosomal dorsal shield) with reduced genal spines, as well as somite VII (first opisthosomal segment) with reduced appendages and microtergite. References Middle Ordovician first appearances {{Chelicerata-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dekatriata
Dekatriata is a clade of planatergan chelicerates including the groups Arachnida, Chasmataspidida, Eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 million years ago. The group is l ...a and additionally two stem-genera '' Winneshiekia'' and '' Houia''. Dekatriata is defined by an opisthosoma with 13 segments as groundplan (the number proposed to be secondarily reduced in most arachnid orders) and fused, plate-like appendages on the first opisthosomal segment (somite VII). References Middle Ordovician first appearances {{Chelicerata-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), 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 Celtic Britons, 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 (geology), rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed Stratum, 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 Union of Geological Sciences, Intern ... [...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] |
Pasternakevia
''Pasternakevia'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Pasternakevia'' was regarded as part of the clade Planaterga. Fossils of the single and type species, ''P. podolica'', have been discovered in deposits of the Silurian period in Podolia, Ukraine. The prosoma of ''Pasternakevia'' covered by a smooth, semicircular carapace with rounded genal cornua (posterolateral corner of carapace). Within the 10-segmented opisthosoma, tergite of the first segment is reduced and usually hidden under the preceding carapace, while the second one is significantly arched and well-developed. All but the first tergite possess well-developed pleurae (lateral extension). A complete telson The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on accou ... is yet to be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bembicosoma
''Bembicosoma'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Bembicosoma'' was regarded as part of the clade Planaterga. Fossils of the single and type species, ''B. pomphicus'', have been discovered in deposits of the Silurian period in the Pentland Hills, Scotland (in the United Kingdom). ''Bembicosoma'' had been tentatively assigned as an eurypterid (sea scorpion) before its synziphosurine affinities revealed. The prosoma of ''Bembicosoma'' covered by a short, semicircular carapace without evidence of ophthalmic ridges. Within the 10-segmented opisthosoma The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma (cephalothorax). It is a distinctive feature of the subphylum Chelicerata (arachnids, horseshoe crabs and others). Although it is similar in most respects to a ..., the first segment is nearly as wide as the carapace but reduced in length while the second segment is the largest. The dorsal surfac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bunaia
''Bunaia'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Bunaia'' was tentatively placed as part of the clade Planaterga. The genus contains at least one species: ''Bunaia woodwardi'' from the Silurian period in Svalbard, Norway. Only a few morphological information of ''B''. ''woodwardi'' had been confirmed, as the species known only from poorly preserved specimens compose of semicircular carapace, fragments of opisthosoma and disarticulated telson. The placement of ''"Bunaia" heintzi'' (known only by a single carapace from the Silurian period in the United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...) within this genus had been questioned and required further investigation. References Synziphosurina Silurian first appea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bunodidae
Bunodidae is an extinct family of synziphosurine chelicerates that lived in the Silurian. Bunodidae is classified inside the clade Planaterga alongside Pseudoniscidae and Dekatriata ( chasmataspidids, eurypterids and arachnids). Bunodidae is composed by two genera, '' Bunodes'' (the type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal f ...) and '' Limuloides''. References Synziphosurina Planaterga Silurian first appearances Silurian arthropods Silurian extinctions Prehistoric arthropod families {{Chelicerata-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudoniscidae
Pseudoniscidae is an extinct Family (biology), family of synziphosurine chelicerates that lived in the Silurian. Pseudoniscidae is classified inside the clade Planaterga, alongside Bunodidae and Dekatriata (Chasmataspidida, chasmataspidids, Eurypterid, eurypterids and Arachnid, arachnids). Pseudoniscidae is composed by two genera, ''Cyamocephalus'' and ''Pseudoniscus'' (the type genus). References Synziphosurina Planaterga Silurian first appearances Silurian arthropods Silurian extinctions Prehistoric arthropod families {{Chelicerata-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, the equivalent Latin term ''cladus'' (plural ''cladi'') is often used in taxonomical literature. The common ancestor may be an individual, a population, or a species (extinct or extant). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over the last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic. Some of the relationships between organisms ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prosomapoda
Prosomapoda is a clade of euchelicerates including the groups Xiphosura (horseshoe crabs) and Planaterga (a group comprising bunodids, pseudoniscids, chasmataspidids, eurypterids and arachnids), as well as several basal synziphosurid genera. The clade is defined by the lack of exopods (outer branches) of prosomal appendage II-V in the adult instar, where in contrast the exopods of appendage II-V are well-developed in the non-prosomapod euchelicerates '' Offacolus'' and ''Dibasterium ''Dibasterium'' is an extinct genus of euchelicerate, a group of chelicerate arthropods. Fossils of the single and type species, ''D. durgae'', have been discovered in the Coalbrookdale Formation of the Middle Silurian period (Homerian age) in ...''. References Middle Ordovician first appearances {{Chelicerata-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chelicerate
The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mites, among many others), as well as a number of extinct lineages, such as the eurypterids (sea scorpions) and chasmataspidids. The Chelicerata originated as marine animals in the Middle Cambrian period; the first confirmed chelicerate fossils, belonging to '' Sanctacaris'', date from 508 million years ago. The surviving marine species include the four species of xiphosurans (horseshoe crabs), and possibly the 1,300 species of pycnogonids (sea spiders), if the latter are indeed chelicerates. On the other hand, there are over 77,000 well-identified species of air-breathing chelicerates, and there may be about 500,000 unidentified species. Like all arthropods, chelicerates have segmented bodies with jointed limbs, all covered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synziphosurina
Synziphosurina is a paraphyletic group of chelicerate arthropods previously thought to be basal horseshoe crabs (Xiphosura). It was later identified as a grade composed of various basal euchelicerates, eventually excluded form the monophyletic Xiphosura ''sensu stricto'' and only regarded as horseshoe crabs under a broader sense ('Xiphosura' ''sensu lato''). Synziphosurines survived at least since early Ordovician to early Carboniferous in ages, with most species are known from the in-between Silurian strata. File:20200920 Synziphosurina dorsal segmentation.png, Dorsal morphology and variation of opisthosomal segmentation across synziphosurines. While ''Weinbergina'' and ''Willwerathia'' being exceptionally large, most synziphosurines are small arthropods with body length ranging only about a few centimeters long. The body of synziphosurine composed of a prosoma covered by a dome-like carapace (prosomal dorsal shield) and an opisthosoma with usually unfused 9-11 segments expre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
