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Mandibulate
Mandibulata, termed "mandibulates", is a clade of arthropods that comprises the extant subphyla Myriapoda (millipedes and others), Crustacea and Hexapoda (insects and others). Mandibulata is currently believed to be the sister group of the clade Arachnomorpha, which comprises the rest of arthropods (Chelicerata and Trilobita). The mandibulates constitute the largest and most varied arthropod group. The name "Mandibulata" refers to the mandibles or jaws, which are the characterizing feature of its member arthropods. Molecular phylogenetic studies suggest that the living arthropods are related as shown in the cladogram below. Crustaceans do not form a monophyletic group as insects and other hexapods have evolved from within them. See also * Atelocerata *Marrellomorpha *Myriochelata *Pancrustacea Pancrustacea is the clade that comprises all crustaceans and hexapods. This grouping is contrary to the Atelocerata hypothesis, in which Myriapoda and Hexapoda are sister taxa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acheronauta
''Acheronauta'' is a genus of extinct vermiform arthropod that lived in the early Silurian (Telychian-Sheinwoodian stages) Waukesha Biota, Waukesha biota fossil site in southeast Wisconsin. This arthropod was first discovered alongside the biota in 1985, but wasn't fully described until October 2022. This creature was recognized and described as a possible early Mandibulata, mandibulate (the grouping of arthropods including crustaceans and Hexapoda, hexapods). This description is very important as much of the fauna of the biota remain undescribed, and it's discovery has allowed for Paleontology, paleontologists to get a better grasp of the diversity of the arthropod fauna at the site. Multiple phylogenetic analyses were preformed, and it seems that this arthropod forms a previously undiscovered clade with the Devonian stem-arthropod ''Captopodus'', and the somewhat enigmatic group Thylacocephala. ''Acheronauta'' has been assessed as a possible Basal (phylogenetics), basal mandibul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hymenocarina
Hymenocarina is an order of extinct arthropods known from the Cambrian. They possess bivalved carapaces, typically with exposed posteriors. Members of the group are morphologically diverse and had a variety of ecologies, including as filter feeders and as predators. Recent research has generally considered them to be stem or crown group members of Mandibulata, due the presence of mandibles in at least some species. Taxonomy Hymenocarines are characterized by the combination of following characters: bivalved, convex carapace covering cephalothoracic region; cephalothorax bearing multisegmented antennules and rounded mandibles, alongside post-maxillular limbs with spiny, subdivided basis and endopods with well-developed terminal claws; absence of appendages between antennules and mandibles; median sclerite and lobate protrusions located between compound eyes; posterior tagma (abdomen) with ring-like segments and terminated by a pair of well-developed caudal rami. Based on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropoda
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arthropod cuticle, cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. Arthropods are bilaterally symmetrical and their body possesses an exoskeleton, external skeleton. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. Some species have wings. They are an extremely diverse group, with up to 10 million species. The haemocoel, an arthropod's internal cavity, through which its haemolymph – analogue of blood – circulates, accommodates its interior Organ (anatomy), organs; it has an open circulatory system. Like their exteriors, the internal or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thylacocephala
The Thylacocephala (from the Greek or ', meaning " pouch", and or ' meaning "head") are a unique grouping of extinct probable mandibulate arthropods, that have been considered by some researchers as having possible crustacean affinities. As a class they have a short research history, having been erected in the early 1980s. They typically possess a large, laterally flattened carapace that encompasses the entire body. The compound eyes tend to be large and bulbous, and occupy a frontal notch on the carapace. They possess three pairs of large raptorial limbs, and the abdomen bears a battery of small swimming limbs. Inconclusive claims of thylacocephalans have been reported from the lower lower Cambrian ('' Zhenghecaris''), but later study considered that genus as radiodont or arthropod with uncertain systematic position. The oldest unequivocal fossils are Upper Ordovician and Lower Silurian in age. As a group, the Thylacocephala survived to the Santonian stage of the Upper C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fuxianhuiida
Fuxianhuiida is an extinct clade of arthropods from the Cambrian of China. All currently known species are from Cambrian Series 2 aged deposits in Yunnan Province, including the Chengjiang biota. They are generally considered to be close to the base of Euarthropoda, but have also been considered to be early mandibulates. Many specimens are known with exceptional soft tissue preservation, including preserved guts and neural tissue, which given their basal phylogenetic position makes them important in understanding the evolution of arthropoda as a whole. They reach a size of up to 15 cm, and are interpreted as benthic predators and scavengers. The fuxianhuiid exoskeleton is unmineralised, and the number of tergites ranges from 15 to over 40. The cephalon is covered by a head shield and contains stalked eyes connected by the anterior sclerite, antennae, a butterfly shaped hyposome and a posterior facing mouth. Fuxianhuiids possess specialized post-antennal appendages with se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euthycarcinoidea
Euthycarcinoidea are an enigmatic group of extinct possibly amphibious arthropods that ranged from Cambrian to Triassic times. Fossils are known from Europe, North America, Argentina, Australia and Antarctica. Description The euthycarcinoid body was divided into a cephalon (head), preabdomen, and postabdomen. The cephalon consisted of two segments and included mandibles, antennae and presumed eyes. The preabdomen consisted of five to fourteen tergites, each having up to three somites. Each somite had in turn a pair of uniramous, segmented legs. The postabdomen was limbless and consisted of up to six segments and a terminal tail spine. Affinities Due to its particular combination of characteristics, the position of the Euthycarcinoidea within the Arthropoda has been ambiguous; previous authors have allied euthycarcinoids with crustaceans (interpreted as copepods, branchiopods, or an independent group), with trilobites, or the merostomatans (horseshoe crabs and sea scorpions, no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphatocopina
Phosphatocopina (alternatively Phosphatocopida) is an extinct group of bivalved arthropods known from the Cambrian period. They are generally sub-milimetric to a few millimetres in size, and are typically found 3-dimensionally preserved in Orsten-type phosphatized preservation. Description The phosphatized bivalved carapace covered the entire body. In some species, spines were present on the carapace. The head either bore a pair of stalked eyes or a pair of dome-shaped medial eyes. The first appendage pair, dubbed the "antennulae", were uniramous, with the remaining appendage pairs being biramous. The endopods of the biramous limbs had prominently developed endites, while the exopods were typically annulated, and bore setae. The earliest larval stages of phosphatocopines are known as "head larva", due to them only having the four pairs of cephalic appendages. Ecology Phosphatocopines are generally thought to have been nektobenthic (swimming close to the sediment), and ha ... [...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 The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquilonifer
''Aquilonifer spinosus'' is an extinct species of arthropod from the Silurian period. It is known from a single fossil specimen found in the Wenlock Series Lagerstätte of Herefordshire, England, in rocks about 430 million years old. The 1 cm long specimen is a stem-group mandibulate, not directly related to any living species. The many-legged, eyeless adult has ten unusual tethered appendages, interpreted as juveniles attached to the parent, in a unique form and previously unknown brooding behaviour. Etymology "Aquilone" is Italian for "toy kite", and the suffix "–ifer" means "to carry". "Spinosus" means "spiny" in Latin. Its discoverers have nicknamed it "the kite runner ''The Kite Runner'' is the first novel by Afghan-American author Khaled Hosseini. Published in 2003 by Riverhead Books, it tells the story of Amir, a young boy from the Wazir Akbar Khan district of Kabul. The story is set against a backdrop ...". References Silurian arthropods of Euro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mandible (arthropod Mouthpart)
250px, The mandibles of a bull ant The mandible (from la, mandibula or mandĭbŭ-lum, a jaw) of an arthropod is a pair of mouthparts used either for biting or cutting and holding food. Mandibles are often simply called jaws. Mandibles are present in the extant subphyla Myriapoda (millipedes and others), Crustacea and Hexapoda (insects etc.). These groups make up the clade Mandibulata, which is currently believed to be the sister group to the rest of arthropods, the clade Arachnomorpha (Chelicerata and Trilobita). Unlike the chelicerae of arachnids, mandibles can often be used to chew food. Mandibulates also differ by having antennae, and also by having three distinct body regions: head, thorax and abdomen. (The cephalothorax (or prosoma) of chelicerates is a fusion of head and thorax.) Insects Insect mandibles are as diverse in form as their food. For instance, grasshoppers and many other plant-eating insects have sharp-edged mandibles that move side to side. Most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Phylogenetics
Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to determine the processes by which diversity among species has been achieved. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree. Molecular phylogenetics is one aspect of molecular systematics, a broader term that also includes the use of molecular data in taxonomy and biogeography. Molecular phylogenetics and molecular evolution correlate. Molecular evolution is the process of selective changes (mutations) at a molecular level (genes, proteins, etc.) throughout various branches in the tree of life (evolution). Molecular phylogenetics makes inferences of the evolutionary relationships that arise due to molecular evolution and results in the construction of a phylogenetic tree. History The theoretical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
