|
Yohoia
''Yohoia'' is an extinct genus of megacheiran arthropod from the Cambrian period that has been found as fossils in the Burgess Shale formation of British Columbia, Canada. It has been placed among the arachnomorpha, a group of arthropods that includes the chelicerates and possibly the trilobites. Fossils range in size from 7 to 23 mm. 711 specimens of ''Yohoia'' are known from the Greater Phyllopod bed, where they comprise 1.35% of the community. ''Yohoia'' is one of the "great appendage" arthropods. All taxa have a single pair of large pre-oral jointed limbs with branched spiny ends for grasping, impaling, or filtering food items. "Great appendage" arthropods have been seen as a polyphyletic group where the appendage has independently evolved, or as a Class Megacheira including ''Yohoia'' (with ''Leanchoilia'', ''Alalcomenaeus'', ''Oestokerkus'', ''Fortiforceps'', ''Jianfengia'', ''Yawunik'') defined as euarthropods, plus the radiodonts, defined as a sister group to arthro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megacheira
Megacheira ("great hands") is an extinct class of predatory arthropods that possessed a pair of great appendages, hence the class name as well as the common name "great appendage arthropods". Their taxonomic position is controversial, with studies either considering them stem-group euarthropods, or stem-group chelicerates. Most of them were found in marine environments throughout the world from the lower to middle Cambrian. Megacheirans were important components of several faunas, including the Burgess, Wheeler and Maotianshan Shales Lagerstatten. Homology of great appendages The homology between megacheiran great appendages and cephalic appendages of other arthropods had been discussed for decades. There is controversy over whether they are homologous to both dinocaridid (radiodonts and gilled lobopodians) frontal appendages, the frontalmost appendages of ''Isoxys'' and chelicerates' chelicerae. Based on neuroanatomical evidences, many studies support their homology to ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Burgess Shale Fossils
The fossils of the Burgess Shale, like the Burgess Shale itself, formed around 505 million years ago in the Mid Cambrian period. They were discovered in Canada in 1886, and Charles Doolittle Walcott collected over 65,000 specimens in a series of field trips up to the alpine site from 1909 to 1924. After a period of neglect from the 1930s to the early 1960s, new excavations and re-examinations of Walcott's collection continue to reveal new species, and statistical analysis suggests that additional discoveries will continue for the foreseeable future. Stephen Jay Gould's book '' Wonderful Life'' describes the history of discovery up to the early 1980s, although his analysis of the implications for evolution has been contested. The fossil beds are in a series of shale layers, averaging and totalling about in thickness. These layers were deposited against the face of a high undersea limestone cliff. All these features were later raised up above current sea level during the cr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great Appendage
Great appendages are claw-like appendages which attach to the heads of the "great appendage arthropods", a name usually refers to Megacheira, a class of extinct arthropod characterized by a pair of "short-great appendages" bearing in front of the animal's head. In general, megacheiran's great appendage have 6 segments, with the two proximal segments forming a peduncle and the four finger-like distal segments forming a claw, both connected by an elbow joint. Great appendages have been interpreted as raptorial limbs involved in predation, with those of some genera such as ''Yohoia'' being structurally comparable to the raptorial maxillipeds of mantis shrimp. The great appendages of leanchoilid megacheirans such as ''Leanchoilia'' and ''Yawunik'' have elongated flagella, suggesting a sensory role alongside predatory function. Radiodonta, Radiodont's frontal appendages have controversial relationships to those of the megacheirans. They have been suggested to be Homology (biology), ho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alalcomenaeus
''Alalcomenaeus'' is one of the most widespread and longest-surviving arthropod genera of the Early and Middle Cambrian. Known from over 300 specimens in the Burgess Shale and the Chengjiang biota. it is a member of the group Megacheira. Morphology ''Alalcomenaeus'' had three median eyes; two stalked, more lateral eyes; a triflagellate great appendage; and two more head appendages posterior to that. Like its body appendages, these were biramous—their inner branch was spiny, segmented, flexible and leg-like, while the outer portion had a large surface area and resembled a flap. ''Alalcomenaeus'' reached about 6 cm in length, although many smaller specimens are known. Its head was covered with a shield, and its eleven body segments were also covered with an exoskeleton. Its body terminated with a paddle-like telson ("tail") which probably helped to propel the organism; this ended with long flat spikes in the plane of the tail fin. Ecology The organism probably swam, waft ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arachnomorpha
Arachnomorpha is a proposed subdivision or clade of Arthropoda, comprising the group formed by the trilobites and their close relatives (Artiopoda), Megacheira (which may be paraphyletic) and chelicerates. Under this proposed classification scheme, Arachnomorpha is considered the sister group to Mandibulata (including insects, crustaceans and myriapods). The arachnomorph concept has been challenged by suggestions that the artiopods are more closely related to mandibulates, forming the clade Antennulata instead. There is no consensus as to assigning Arachnomorpha a formal Linnean rank. Classification Arachnomorpha Lameere, 1890 Arachnata Paulus, 1979, = Palaeopoda Packard, 1903*†Trilobita Walch, 1771 *†Megacheira Hou & Bergstrom, 1997 *†Strabopida Hou & Bergström, 1997 *† Aglaspida Walcott, 1911 *† Cheloniellida Broili, 1932 *Chelicerata Heymons 1901 **Family † Sanctacarididae Legg & Pates, 2017 **Class Pycnogonida Latreille, 1810 **Clade Euchelicerata Weygoldt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chelicerata
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 Opiliones, harvestmen, scorpions, spiders, Solifugae, solifuges, Parasitiformes, ticks, and Acariformes, 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 Burgess Shale, 508 million years ago. The surviving marine species include the four species of xiphosurans (horseshoe crabs), and possibly the 1,300 species of Pycnogonida, 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 arth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiodonta
Radiodonta is an extinct Order (biology), order of stem-group arthropods that was successful worldwide during the Cambrian period. They may be referred to as radiodonts, radiodontans, radiodontids, anomalocarids, or anomalocaridids, although the last two originally refer to the family Anomalocarididae, which previously included all species of this order but is now restricted to only a few species. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and used for a variety of functions. Radiodonts included the earliest large predators known, but they also included sediment sifters and filter feeders. Some of the most famous species of radiodonts are the Cambrian taxa ''Anomalocaris, Anomalocaris canadensis'', ''Hurdia, Hurdia victoria'', ''Peytoia nathorsti'', ''Titanokorys gainesii, Titanokorys gainessii, Cambroraster, Cambroraster falcatus'' and ''Amplectobelua, Amplectobelua symbrachiata'', the Ordovician ''Aegirocassis, Aegiroca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Doolittle Walcott
Charles Doolittle Walcott (March 31, 1850February 9, 1927) was an American paleontologist, administrator of the Smithsonian Institution from 1907 to 1927, and director of the United States Geological Survey.Wonderful Life (book) by Stephen Jay Gould published in 1989, Chapter 4 He is famous for his discovery in 1909 of well-preserved fossils, including some of the oldest soft-part imprints, in the Burgess Shale of British Columbia, Canada. Early life Charles Doolittle Walcott was born on March 31, 1850 in New York Mills, New York. His grandfather, Benjamin S. Walcott, moved from Rhode Island in 1822. His father, also Charles Doolittle Walcott, died when Charles Jr. was only two. Walcott was the youngest of four children. He was interested in nature from an early age, collecting minerals and bird eggs and, eventually, fossils. He attended various schools in the Utica area but left at the age of eighteen without completing high school, the end of his formal education. His intere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yawunik
''Yawunik'' is an extinct genus of Cambrian megacheiran ("Great appendage" arthropod) known from the Burgess Shale in Canada (Marble Canyon locality). The type species has been named ''Yawunik kootenayi'' after the Kootenay, both a geographic area (and National Park, where the fossil was found) and North American First Nation, also known as the Ktunaxa. Yawunik is the name of a primordial sea monster in Ktunaxa mythology. The fossil dates back to 508 million years ago. Description ''Yawunik'' had large size for megacheiran, up to long not including great appendage. It had four eyes, in the anteriormost position of the head, and lateral eyes are larger. ''Yawunik'' differs from other leanchoilid such as ''Leanchoilia ''Leanchoilia'' is an megacheiran arthropod known from Cambrian deposits of the Burgess Shale in Canada and the Chengjiang biota of China. It was about long and had long, whip-like feelers mounted on frontal arm-like appendages. Its internal o ...'' by havi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taxa Named By Charles Doolittle Walcott
In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and given a particular ranking, especially if and when it is accepted or becomes established. It is very common, however, for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion. If a taxon is given a formal scientific name, its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping. Initial attempts at classifying and ordering organisms (plants and animals) were set forth in Carl Linnaeus's system in '' Systema Naturae'', 10th edition (1758), as well as an unpublished work by Bernard and Antoine Laurent de Jussieu. The idea of a unit-based system of biological classification was first made widely available in 1805 in the i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Burgess Shale Animals
__NOTOC__ Burgess may refer to: People and fictional characters * Burgess (surname), a list of people and fictional characters * Burgess (given name), a list of people Places * Burgess, Michigan, an unincorporated community *Burgess, Missouri, United States * Burgess, South Carolina, United States *Burgess, Virginia, United States *Burgess Township, Bond County, Illinois, United States *Burgess Park, London, England *Burgess Field Oxford, England *Burgess Hill, Sussex, England *Mount Burgess, Canadian Rockies *Burgess Branch, a tributary of Missisquoi River, Vermont, United States Other uses *Burgess (title), a political official or representative *Burgess Company, an American airplane manufacturer *Burgess GAA, an athletic club in Ireland See also *Burgess House (other), several buildings named *Burgess model, or Concentric zone model, a theoretical model in urban geography *Burgess reagent, used in organic chemistry *Burgess Shale, a fossil-bearing formation near Mount ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prehistoric Arthropod Genera
Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use of symbols, marks, and images appears very early among humans, but the earliest known writing systems appeared 5000 years ago. It took thousands of years for writing systems to be widely adopted, with writing spreading to almost all cultures by the 19th century. The end of prehistory therefore came at very different times in different places, and the term is less often used in discussing societies where prehistory ended relatively recently. In the early Bronze Age, Sumer in Mesopotamia, the Indus Valley Civilisation, and ancient Egypt were the first civilizations to develop their own scripts and to keep historical records, with their neighbors following. Most other civilizations reached the end of prehistory during the following Iron Age. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
