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Euarthropods
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, often 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 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 organs; it has an open circulatory system. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. Their nervous system is "ladder-lik ... [...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] |
Lobopodia
The lobopodians, members of the informal group Lobopodia (from the Greek language, Greek, meaning "blunt feet"), or the formally erected phylum Lobopoda Cavalier-Smith (1998), are panarthropods with stubby legs called lobopods, a term which may also be used as a common name of this group as well. While the definition of lobopodians may differ between literatures, it usually refers to a group of soft-bodied, worm-like fossil panarthropods such as ''Aysheaia'' and ''Hallucigenia''. The oldest near-complete fossil lobopodians date to the Lower Cambrian; some are also known from Ordovician, Silurian and Carboniferous Lagerstätten. Some bear toughened claws, plates or spines, which are commonly preserved as small carbonaceous fossil, carbonaceous or Small Shelly Fossils, mineralized microfossils in Cambrian strata. The grouping is considered to be paraphyletic, as the three living panarthropod groups (Arthropoda, Tardigrada and Onychophora) are thought to have evolved from lobopodian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erratus
''Erratus'' is an extinct genus of marine arthropod from the Cambrian of China. Its type and only species is ''Erratus sperare''. ''Erratus'' is likely one of the most basal known arthropods, and its discovery has helped scientists understand the early evolution of arthropod trunk appendages. Some of the stem-arthropods like radiodonts did not have legs, instead they had flap like appendages that helped them swim. ''Erratus'' on the other hand had not only flaps but also a set of primitive legs. It also supported the theory that the gills of aquatic arthropods probably evolved into the wings and lungs of terrestrial arthropods later in the Paleozoic. Fossils of ''Erratus'' have been found in the Chengjiang Lagerstätte of China, dating to around 520 million years ago. ''Erratus'' was a small, nektonic organism with a bivalved carapace that probably ate by deposit feeding or filter feeding. History of study The holotype consists of specimens XDBZ101 and XDBZ102. The paratype spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dinocaridida
DinocarididaGreek, "Terrible crabs" – sometimes informally spelt Dinocarida, but the second 'id' is linguistically correct – see is a proposed fossil taxon of basal arthropods that flourished in the Cambrian period with occasional OrdovicianVan Roy, P.; Briggs, D. E. G. (2011). "A giant Ordovician anomalocaridid". Nature 473 (7348): 510–513. doi:10.1038/nature09920. edit and Devonian records. Characterized by a pair of frontal appendages and series of body flaps, the name of Dinocaridids comes from Greek language, Greek, "deinos" and "caris" ("terrible crab"), referring to the suggested role of some of these members as the largest Marine life, marine Predation, predators of their time. Dinocaridids are occasionally referred to as the 'AOPK group' by some literatures, as the group compose of Radiodonta (''Anomalocaris'' and relatives), Opabiniidae (''Opabinia'' and relatives), ''Pambdelurion'' and ''Kerygmachela.'' It is most likely paraphyletic, with ''Kerygmachela'' and ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anomalocaris
''Anomalocaris'' ("unlike other shrimp", or "abnormal shrimp") is an extinct genus of Radiodonta, radiodont, an Order (biology), order of early-diverging stem-group arthropods. The first fossils of ''Anomalocaris'' were discovered in the ''Ogygopsis'' Shale of the Stephen Formation in British Columbia, Canada by Joseph Frederick Whiteaves, with more examples found by Charles Doolittle Walcott in the Burgess Shale unit of the Stephen Formation. Other closely related fossils have been found in the older Emu Bay Shale of Australia, as well as possibly elsewhere. Originally several fossilized parts discovered separately (the mouth, frontal appendages and trunk) were thought to be three separate creatures, a misapprehension corrected by Harry B. Whittington and Derek Briggs in a 1985 journal article. With a body length close to 40 centimetres, ''A. canadensis'' is thought to be one of the earliest examples of an apex predator, though others have been found in older Cambrian lagerstätte ... [...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] |
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] |
Kylinxia
''Kylinxia'' is a genus of extinct arthropod described in 2020. It was described from six specimens discovered in Yu'anshan Formation (Maotianshan Shales) in southern China. The specimens are assigned to one species ''Kylinxia zhangi.'' Dated to 518 million years, the fossils falls under the Cambrian period. Announcing the discovery on 4 November 2020 at a press conference, Zeng Han of the Nanjing Institute of Geology and Paleontology, said that the animal "bridges the evolutionary gap from ''Anomalocaris'' to true arthropods and forms a key ‘ missing link’ in the origin of arthropods," which was "predicted by Darwin’s evolutionary theory." The same day the formal description was published in ''Nature''. Discovery ''Kylinxia zhangi'' was discovered among the Maotianshan Shales from Yu'anshan Formation at Yunnan in southern China in 2019. Zeng Han, Zhao Fangchen, and Huang Diying of the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, made the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opabiniidae
Opabiniidae is an extinct family of bizarre marine stem-arthropods. Its type and best-known genus is ''Opabinia''. It also contains ''Utaurora''. Opabiniids closely resemble radiodonts, but their frontal appendages were basally fused into a proboscis. Opabiniids also distinguishable from radiodonts by setal blades covering at least part of the body flaps and serrated caudal rami. History of study Opabiniidae was named by Charles Doolittle Walcott in 1912, alongside its type species ''Opabinia''. Walcott interpreted Opabiniidae as a family of anostracan crustaceans, most closely related to Thamnocephalidae. ''Opabinia'' was restudied in the 1970s, and reinterpreted as a stranger animal. Stephen Jay Gould referred to ''Opabinia'' as a "weird wonder", and an illustration of ''Opabinia'' prompted laughter when it was first revealed at a paleontological conference. In 2022, a second opabiniid, ''Utaurora'', was identified. ''Myoscolex'' from Emu Bay Shale is sometimes suggested to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trilobite
Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period () and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described. By the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. Because trilobites had wide diversity and an easily fossilized exoskeleton, they left an extensive fossil record. The stu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trilobita
Trilobites (; meaning "three lobes") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the Atdabanian Stage (geology), stage of the Early Cambrian Period (geology), period () and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in Permian–Triassic extinction event, the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described. By the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. Because trilobites had ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Artiopoda
The Artiopoda is a grouping of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomorpha. Hou and Bergström used the name Lamellipedia as a superclass to replace Trilobitomorpha that was originally erected at the subphylum level, which they considered inappropriate. Trilobites, in part due to their mineralising exoskeletons, are by far the most diverse and long lived members of the clade, with most records of other members, which lack mineralised exoskeletons, being from Cambrian deposits. Description According to Stein and Selden (2012) artiopods are recognised by the possession of filiform antennulae, limbs with bilobate exopods, with the proximal lobe being elongate and bearing a lamella, while the distal lobe is paddle-shaped and setiforous (bearing hair-or bristle like structures). The limb endopod has se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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