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  • Trilobites
  • Trilobites are an extinct group of arthropods that first appeared early in the Cambrian Period, and met their demise at the end of the Permian Period. (trilobites.com)
  • Trilobites were stunningly complex and beautiful animals, which is why their fossilized remains are extremely sought-after by serious fossil collectors. (trilobites.com)
  • And due to their unique anatomy and bizarre body designs, trilobites are also admired by untrained amateurs. (trilobites.com)
  • Fossil trilobites have been found in Native American excavations - they were drilled and used in ritualistic jewelry hundreds of years ago. (trilobites.com)
  • It is not that unusual to find enrolled trilobites in the fossil record. (trilobites.com)
  • Trilobites had remarkably sophisticated eyes for ancient, "primitive" creatures. (trilobites.com)
  • Although some trilobites were blind, many had large, compound eyes, much like modern insects, with hundreds of individual lenses. (trilobites.com)
  • Despite all these changes and adaptations, trilobites did not stray far away from their original body plan during millions of years of evolution. (trilobites.com)
  • Tracks and trails of trilobites have long been recognized as trace fossils. (trilobites.com)
  • Trilobites are favorites of fossil collectors everywhere due to their unique design and varied forms of preservation. (trilobites.com)
  • The eyes were 30 times as powerful as those of trilobites, long thought to have had the most advanced eyes of any contemporary species. (wikipedia.org)
  • One of the best-known groups of fossil animal are the trilobites ('three-lobed'), this name deriving from the distinctive three-lobed structure of their body, which consists of the cephalon (head shield), the thorax, and the pygidium (tail shield). (blogspot.co.uk)
  • They were initially deemed to be ancient, three-lobed clam-like seashells (and were duly dubbed Concha triloba ), because these particular trilobite fossils showed only the animals' dorsal side (thereby concealing the fact that trilobites actually possessed legs - lots of legs, in fact! (blogspot.co.uk)
  • The matter remained contentious until American palaeontologist Charles D. Walcott resolved it in a very convincing manner - by skilfully and painstakingly using a hacksaw to open up no fewer than 3,500 fossils of curled-up trilobites, thereby revealing the presence of their jointed legs, and, in turn, these hitherto-baffling beasts' true nature as arthropods. (blogspot.co.uk)
  • During the lengthy course of their evolution, the trilobites became exceedingly successful, yielding a vast diversity of species (some 17,000 are currently recognised) as well as body forms and lifestyles before decreasing markedly in the Devonian, and finally dying out completely around 252 million years ago (in the mass extinction that occurred at the end of the Permian) - or did they? (blogspot.co.uk)
  • This is usually achieved in trilobites by having lines of weakness - or sutures - at strategic places on the body, which preferentially break. (blogspot.com)
  • genus
  • Some entomologists have suggested a relationship to the Baltic Eocene fossil ant genus Prionomyrmex based on morphological similarities, but this interpretation is not widely accepted by the entomological community. (wikipedia.org)
  • Anomalocaris ("abnormal shrimp") is an extinct genus of anomalocaridid, a family of animals thought to be closely related to ancestral arthropods. (wikipedia.org)
  • In 1960 Russian paleontologists described specimens they found in the Norilsky region of Siberia and labelled Opabinia norilica, but these fossils were poorly preserved, and Whittington did not feel they provided enough information to be classified as members of the genus Opabinia. (wikipedia.org)
  • Perhaps the best-known genus of eurypterid is Eurypterus, of which around 16 fossil species are known. (wikipedia.org)
  • Indeed, in the most famous genus, North America 's Stegosaurus , their brain was only the size of a walnut whereas their body was the size of a van! (blogspot.nl)
  • closely related
  • However other finds, most notably Anomalocaris, suggested that it belonged to a group of animals that were closely related to the ancestors of arthropods and of which the living animals onychophorans and tardigrades may also be members. (wikipedia.org)
  • There has been much debate as to which arthropod group is most closely related to the Myriapoda. (wikipedia.org)
  • Later discoveries of similar animals and the development of new theoretical approaches led to the conclusion that many of the "weird wonders" were evolutionary "aunts" or "cousins" of modern groups-for example that Opabinia was a member of the lobopods, a group which includes the ancestors of the arthropods, and that it may have been closely related to the modern tardigrades. (wikipedia.org)
  • antennae
  • On closer inspection the mite has no antennae, no wings, 4 pairs of legs, an unsegmented abdomen, and simple eyes. (walterreeves.com)
  • Whereas an insect such as a bee will have 3 body parts, 2 compound eyes, 2 antennae, 4 wings, 3 pairs legs, and a segmented abdomen. (walterreeves.com)
  • The head bears two pairs of antennae, usually one median eye and two lateral eyes, and three pairs of biting mouthparts-the mandibles and the two pairs of maxillae. (encyclopedia.com)
  • The mandibles, clypeus (one of the sclerites that make up the "face" of an arthropod or insect), antennae and legs are pale yellow. (wikipedia.org)
  • The hairs on the body are yellow, erect and long and abundant, but on the antennae and legs they are shorter and suberect (standing almost in an erect position). (wikipedia.org)
  • Myriapods have a single pair of antennae and, in most cases, simple eyes. (wikipedia.org)
  • This xiphosuran chelicerate shows many typical arthropod features both externally and internally, (c) comparison of the structure of the arthropod brain, for example, that of L. polyphemus and a crustacean and (d) might suggest that the chelicerae of the former are homologous to the second antennae of the latter, but this is far from clear. (els.net)
  • Trilobite
  • Bearing in mind how zoologically familiar they are today and how their taxonomic identity as arthropods is indisputable, it may come as something of a surprise to learn that the first trilobite fossils to attract notable scientific attention, during the 1700s, incited considerable controversy as to what type of creature they represented, resulting in some exceedingly bizarre notions being aired in all seriousness. (blogspot.co.uk)
  • thorax
  • the segments tend to be fused together in groups to create distinct body regions such as head, thorax, and abdomen. (scholastic.com)
  • The legs, eyes and mouth are all located on the prosoma and it serves as both a head and a thorax. (wikipedia.org)
  • The isopod body plan consists of a head (cephalon), a thorax (pereon) with eight segments (pereonites), and an abdomen (pleon) with six segments (pleonites), some of which may be fused. (wikipedia.org)
  • eurypterids
  • The body of eurypterids is segmented, as in all arthropods, and may be divided into two basic parts. (berkeley.edu)
  • Eurypterids are believed to have undergone ecdysis, making their significance in ecosystems difficult to assess, because it can be difficult to tell a fossil moult from a true fossil carcass. (wikipedia.org)
  • Behind the head, eurypterids had twelve body segments. (wikipedia.org)
  • Based on the isolated fossil remains of a large chelicera (claw) from the Klerf Formation of Germany, J. rhenaniae has been estimated to have reached a size of around 2.5 metres (8.2 ft), potentially 2.6 metres (8.5 ft), which would make Jaekelopterus the largest known arthropod ever discovered, surpassing other large arthropods such as fellow giant eurypterids Acutiramus and Pterygotus and the giant millipede Arthropleura. (wikipedia.org)
  • The morphology and body construction of Jaekelopterus and other eurypterids in the Pterygotidae suggests they were adapted to a completely aquatic lifestyle. (wikipedia.org)
  • The chelicerata originated as marine animals, possibly in the Cambrian period, but the first confirmed chelicerate fossils, eurypterids, date from 445 million years ago in the Late Ordovician period. (wikipedia.org)
  • Crabs
  • Horseshoe crabs are commonly known by biologists around the world as a living fossil because they have remained practically unchanged in terms of shape and size for millions of years. (wikipedia.org)
  • Horseshoe crabs are marine arthropods of the family Limulidae, suborder Xiphosurida, and order Xiphosura. (wikipedia.org)
  • Because of their origin 450 million years ago, horseshoe crabs are considered living fossils. (wikipedia.org)
  • the modern horseshoe crabs look almost identical to prehistoric genera such as the Jurassic Mesolimulus, and are considered to be living fossils. (wikipedia.org)
  • gills
  • Eyes = Gut == Gills Opabinia looked so strange that the audience at the first presentation of Whittington's analysis laughed. (wikipedia.org)
  • As in other arthropods, a true endoskeleton is absent, but the body does have an endoskeletal structure made up of cartilaginous plates that support the book gills. (wikipedia.org)
  • Xiphosurans have well-developed circulatory systems, with numerous arteries that send blood from the long tubular heart to the body tissues, and then to two longitudinal sinuses next to the gills. (wikipedia.org)
  • carapace
  • It had a large bivalved carapace and a segmented body terminating into a pair of tail flaps. (wikipedia.org)
  • The mangrove horseshoe crab grows up to 40 centimeters in length (including the tail), and its whole body is protected by a hard, dark brown carapace. (wikipedia.org)
  • Xiphosurans have up to four eyes, located in the carapace. (wikipedia.org)
  • segments
  • The main part of the body was typically about 5 millimetres (0.20 in) wide and had 15 segments, on each of which there were pairs of lobes (flaps) pointing downwards and outwards. (wikipedia.org)
  • Millipedes differ from the other groups in having their body segments fused into pairs, giving the appearance that each segment bears two pairs of legs, while the other three groups have a single pair of legs on each body segment. (wikipedia.org)
  • They are distinguished by the fusion of each pair of body segments into a single unit, giving the appearance of having two pairs of legs per segment. (wikipedia.org)
  • Segments tend to be grouped into body regions or tagmata. (els.net)
  • All arthropods are built from many such segments, which may be modified in various ways. (els.net)
  • stalks
  • Each individual eye facet can be made out on the tiny eye stalks, allowing researchers to analyze how the animal viewed and interpreted the world around it. (nbcnews.com)
  • The stalks, which allowed the eye structures to rest above the animal's body, were probably also moveable, so the crustacean would have had an even larger range of view . (nbcnews.com)
  • The eye stalks had specialized sensors that faced inward, toward the space between the two stalks. (nbcnews.com)
  • Anomalocaris had a large head, a single pair of large, compound eyes on stalks comprising approximately 16,000 lenses, and an unusual disk-like mouth. (wikipedia.org)
  • large
  • Prionomyrmex ants are characterised by their large size, slender bodies, elongated mandibles and powerful stingers. (wikipedia.org)
  • Workers are strictly nocturnal (active mainly at night) but navigate by vision, relying on large compound eyes. (wikipedia.org)
  • Anomalocaridids also had large compound eyes, a feature that they share with arthropods. (wikipedia.org)
  • The eyes have a very large range of view, with different parts of the eyes equipped with particularly sized and spaced facets. (nbcnews.com)
  • Exceptions include the large and well-developed compound eyes of Scutigera The mouthparts lie on the underside of the head, with an "epistome" and labrum forming the upper lip, and a pair of maxillae forming the lower lip. (wikipedia.org)
  • The stomach secretes digestive enzymes, and is attached to an intestine and two large caeca that extend through much of the body, and absorb the nutrients from the food. (wikipedia.org)
  • The eyes are large and well developed, the mandibles are subtriangular but poorly preserved, and a sting is present on examined A. systenus fossils. (wikipedia.org)
  • As on land and in the air, marine invertebrates have a large variety of body plans, and have been categorised into over 30 phyla. (wikipedia.org)
  • Arthropods exhibit unparalleled diversity and abundance along with a correspondingly large ecological impact. (els.net)
  • earliest
  • The earliest horseshoe crab fossils are found in strata from the late Ordovician period, roughly 450 million years ago. (wikipedia.org)
  • Global but exclusively marine in distribution, this taxonomic class of arthropods was one of the earliest, with the first-known representatives in the fossil record dating back approximately 540-520 million years to the early Cambrian Period (though it is suspected that there may well have been earlier forms as yet unrepresented by documented fossils dating as far back as 700 million years, to the pre-Cambrian). (blogspot.co.uk)
  • The earliest widely accepted animal fossils are the rather modern-looking cnidarians (the group that includes jellyfish, sea anemones and Hydra), possibly from around 580 Ma The Ediacara biota, which flourished for the last 40 million years before the start of the Cambrian, were the first animals more than a very few centimetres long. (wikipedia.org)
  • absent
  • Although originally interpreted as an anomalocaridid-like arthropod, some recent studies suggest that it may represent an anomalocaridid: if so it would extend the group's record by some hundred million years: the non-mineralised anomalocaridid structure means they are absent from the intermediate fossil record. (wikipedia.org)
  • anomalocaridids
  • Its discovery was astonishing because previously, anomalocaridids were known only from exceptionally well-preserved fossil beds (Lagerstätten) from the Cambrian, 100 million years earlier. (wikipedia.org)
  • Anomalocaridids, such as Anomalocaris, were organisms thought to be distantly related to the arthropods. (wikipedia.org)
  • The Anomalocaridids comprise a group of very early marine animals known primarily from fossils found in Cambrian deposits in China, United States, Canada, Poland and Australia. (wikipedia.org)
  • group
  • One classification scheme has Schinderhannes classified basally to the crown arthropods, but closer to that group than Anomalocaris. (wikipedia.org)
  • The new findings are based on a three-inch-long fossil arthropod known as Fuxianhuia protensa, found in what is now China's Yunnan Province and were described online October 10 in Nature ( Scientific American is part of Nature Publishing Group). (scientificamerican.com)
  • The group has the open circulatory system typical of arthropods, in which a tube-like heart pumps blood through the hemocoel, which is the major body cavity. (wikipedia.org)
  • Arthropods include the only invertebrate group to evolve flight. (els.net)
  • structures
  • Known as mushroom bodies, these structures help to form and store memories. (elifesciences.org)
  • Exquisitely preserved fossils, discovered in Sweden in the 1970s, include six tiny stalked eye structures, each less than 0.01 inches (a third of a millimeter) long. (nbcnews.com)
  • But not even the labyrinthine structures in the eye present an insurmountable barrier to evolution. (scientificamerican.com)
  • ventral
  • Scientists believe the two ventral eyes aid in the orientation of the horseshoe crab when swimming. (wikipedia.org)
  • Also, a pair of ventral eyes is located near the mouth, as well as a cluster of photoreceptors on the telson. (wikipedia.org)
  • segment
  • a pair of each can arise from each body segment. (scholastic.com)
  • Beneath each body segment was a pair of two-branched legs. (trilobites.com)
  • The body ended with what looked like a single conical segment bearing three pairs of overlapping lobes that pointed up and out, forming a tail like a V-shaped double fan. (wikipedia.org)
  • abdomen
  • Their bodies are covered with a tough cuticle, but do not contain any crystalline biominerals, and are divided into an anterior prosoma and a posterior opisthosoma, or abdomen. (wikipedia.org)
  • Typically
  • Typically, arthropods have reproductive systems that are either distinctly male or female, and therefore reproduce sexually. (scholastic.com)
  • The name "millipede" is a compound word formed from the Latin roots millia ("thousand") and pes (gen. pedis) ("foot"), although millipedes typically have between 36 and 400 legs. (wikipedia.org)
  • suggests
  • The fossil record of myriapods reaches back into the late Silurian, although molecular evidence suggests a diversification in the Cambrian Period, and Cambrian fossils exist which resemble myriapods. (wikipedia.org)
  • Historically body plans were thought of as having evolved in rapidly during the Cambrian explosion, but a more nuanced understanding of animal evolution suggests a gradual development of body plans throughout the early Palaeozoic and beyond. (wikipedia.org)
  • Mayer G, Whitington PM, Sunnucks P and Pflüger H‐J (2010) A revision of brain composition in Onychophora (velvet worms) suggests that the tritocerebrum evolved in arthropods. (els.net)
  • ancestors
  • This development set the first arthropods apart from their soft-bodied ancestors, and may be what allowed some early arthropods to crawl out of the water without drying out in the open air or sagging under their own weight. (scholastic.com)
  • arisen
  • In the 1970s there was an ongoing debate about whether multi-celled animals appeared suddenly during the Early Cambrian, in an event called the Cambrian explosion, or had arisen earlier but without leaving fossils. (wikipedia.org)
  • specimen
  • The specimen had no wings and small portions of its legs and eyes were faintly preserved. (wikipedia.org)
  • Macabeemyrma ovata is known only from a single fossil specimen: a mostly complete adult queen, preserved as a compression fossil in fine-grained shale. (wikipedia.org)
  • If the proportions between body length and chelicerae match those of other giant pterygotids, such as Acutiramus and Pterygotus where the ratio between claw size and body length is relatively consistent, the specimen of Jaekelopterus that possessed the chelicera in question would have measured 233 and 259 (average 246) centimetres in length. (wikipedia.org)
  • The holotype specimen is a partial queen which is incomplete, with one forewing and the head fairly preserved, and the other isolated body portions indistinct. (wikipedia.org)
  • early
  • The oldest arachnid fossil dates to the Silurian period 420 mya, while the oldest insect fossil dates to the early Devonian 407 mya. (walterreeves.com)
  • The organism has also prompted novel hypotheses about the classification of early arthropods. (wikipedia.org)
  • Henningsmoenicaris scutula was an early crustacean just a few millimeters long with compound eyes. (nbcnews.com)
  • Later the discovery of a whole series of similar lobopod animals, some with closer resemblances to arthropods, and the development of the idea of stem groups suggested that the Early Cambrian was a time of relatively fast evolution but one that could be understood without assuming any unique evolutionary processes. (wikipedia.org)
  • This early complexity -especially in the optic area-could help to explain the stunning diversity of visual abilities in modern day relatives, such as compound eye vision. (scientificamerican.com)
  • Studies on the chelicerae and compound eyes of Jaekelopterus have revealed that it was an active and powerful predator with high visual acuity and it likely represented an apex predator in the ecosystems of Early Devonian Euramerica. (wikipedia.org)
  • mandibles
  • These ants can be identified by their long slender bodies, powerful stingers and elongated mandibles. (wikipedia.org)
  • The ant has a long stinger, the body is slender and, like Prionomyrmex, has elongated mandibles. (wikipedia.org)
  • animals
  • The arthropods, or "joint-footed" animals, also fill every imaginable environment, from the deepest ocean trenches to the highest mountain peaks, from the frozen wasteland of Antarctica to the broiling Mojave Desert in the western United States. (scholastic.com)
  • Like all animals, arthropods need oxygen to survive. (scholastic.com)
  • Such animals combine the signals from both eyes to form an image in the brain. (nbcnews.com)
  • Older compound eyes have been found , but the fossils aren't complete enough to determine to this extent how the animals carrying them saw. (nbcnews.com)
  • The fluid-filled pseudocoelom of these animals can function as a hydrostatic skeleton , which can be useful in drilling through soil or a host's body tissue. (psu.edu)
  • Despite having relatively poor eyesight, the animals have the largest rods and cones of any known animal, about 100 times the size of humans', and their eyes are a million times more sensitive to light at night than during the day. (wikipedia.org)
  • ants
  • Fossil Prionomyrmecini ants were once found throughout Europe, possibly nesting in trees and preferring jungle habitats. (wikipedia.org)
  • Fossil Prionomyrmecini ants existed in Europe during the Eocene and Late Oligocene. (wikipedia.org)
  • Fossils of Avitomyrmex, along with other extinct Myrmeciinae ants were first studied and described by Bruce Archibald, Stefan Cover and Corrie Moreau of the Museum of Comparative Zoology in Cambridge, Massachusetts. (wikipedia.org)
  • species
  • The classification of the order Decapoda and overall the class Crustacea have always been a difficult task due to their morphological diversity and the lack of a fossil record amongst its species (Martin and Davis, 2001). (tolweb.org)
  • The genus contains thirteen described species known from Late Cretaceous fossils found in Asia and Europe. (wikipedia.org)
  • All the species were based on fossils in the private collection of James Zigras and loaned to the American Museum of Natural History for paleoentomologists to study. (wikipedia.org)
  • Trogiomorpha is the smallest suborder of the Psocoptera sensu stricto (i.e. excluding Phthiraptera), with about 340 species in 7 families, ranging from the monospecific fossil family Archaeotropidae to the speciose Lepidopsocidae (over 200 species). (wikipedia.org)
  • Most species are herbivorous as nymphs, feeding on submerged leaves and benthic algae, but many are hunters of other aquatic arthropods. (wikipedia.org)
  • Most species have 20 body segments, bearing 11 pairs of leaf-like phyllopodia (swimming legs), and the body lacks a carapace. (wikipedia.org)
  • Phenotypic plasticity within taxa makes species-level identification difficult, and is further compounded by variation in the mode of reproduction. (wikipedia.org)
  • The septa of such species also enable them to change the shapes of individual segments, which facilitates movement by peristalsis ("ripples" that pass along the body) or by undulations that improve the effectiveness of the parapodia. (wikipedia.org)
  • In species with incomplete septa or none, the blood circulates through the main body cavity without any kind of pump, and there is a wide range of locomotory techniques - some burrowing species turn their pharynges inside out to drag themselves through the sediment. (wikipedia.org)
  • Since annelids are soft-bodied, their fossils are rare - mostly jaws and the mineralized tubes that some of the species secreted. (wikipedia.org)
  • The species was named after the two mountains connected by the Fossil Ridge containing the Burgess Shale locality, Mount Wapta and Mount Field of Yoho National Park, British Columbia, Canada. (wikipedia.org)
  • Because trilobites had wide diversity and an easily fossilized exoskeleton, an extensive fossil record was left behind, with some 17,000 known species spanning Paleozoic time. (wikipedia.org)
  • There are approximately 12,000 named species classified into 16 orders and around 140 families, making Diplopoda the largest class of myriapods, an arthropod group which also includes centipedes and other multi-legged creatures. (wikipedia.org)
  • The mouthparts or eyes are smaller or missing in some species and forms. (wikipedia.org)
  • absent
  • Although originally interpreted as an anomalocaridid-like arthropod, some recent studies suggest that it may represent an anomalocaridid: if so it would extend the group's record by some hundred million years: the non-mineralised anomalocaridid structure means they are absent from the intermediate fossil record. (wikipedia.org)
  • They generally possess compound eyes and a carapace, which may be a shell of two valves enclosing the trunk (as in most Cladocera), broad and shallow (as in the Notostraca), or entirely absent (as in the Anostraca). (wikipedia.org)
  • But he noted the almost absent trilobation of body and the difference in the number of segments in the thorax (10 in B. barriensis and 8 in Isotelus). (wikipedia.org)
  • segments
  • These segments are (hopefully) homologous with the segmentation present in all modern arthropods. (blogspot.ru)
  • The vetulicolian body comprises two parts: a voluminous anterior forebody, tipped with an anteriorly positioned mouth, and lined with a row of five round to oval-shaped features on each lateral side, which have been interpreted as gills - or at least openings in the vicinity of the pharynx, and a posterior section that primitively comprises seven segments, and functions as a tail. (wikipedia.org)
  • The body of a fairy shrimp is elongated and divided into segments. (wikipedia.org)
  • The nervous system consists of two nerve cords which run the length of the body, with two ganglia and two transverse commissures in most of the body segments. (wikipedia.org)
  • Most millipedes have very elongated cylindrical or flattened bodies with more than 20 segments, while pill millipedes are shorter and can roll into a ball. (wikipedia.org)
  • 2001
  • Classification of Crustacea is based on a variety of methods including the use of cladistics, molecular systematics, developmental genetics, sperm morphology, larval morphology and fossil record (Martin and Davis, 2001). (tolweb.org)
  • The general scientific consensus formerly (before 2001) considered them early limbless arthropods, but now considers them early deuterostomes. (wikipedia.org)
  • mistakenly
  • the fossils were mistakenly identified as "shrimp", but always with their "heads" missing), the mouth was thought to have been a fossilized jellyfish called Peytoia, and the body, thought to be a sponge named "Laggania" was not associated with either. (wikipedia.org)
  • known
  • They have been known to lift objects 85 times their own body weight. (blogspot.ru)
  • The smallest wasps are solitary chalcid wasps in the family Mymaridae, including the world's smallest known insect, with a body length of only 0.139 mm (0.0055 in), and the smallest known flying insect, only 0.15 mm (0.0059 in) long. (wikipedia.org)
  • Stoneflies are believed to be one of the most primitive groups of Neoptera, with close relatives identified from the Carboniferous and Lower Permian geological periods, while true stoneflies are known from fossils only a bit younger. (wikipedia.org)
  • Large groups of such particles are known to assemble themselves into thermodynamically stable, structurally well-defined arrays, quite reminiscent of one of the 7 crystal systems found in metallurgy and mineralogy (e.g. face-centered cubic, body-centered cubic, etc. (wikipedia.org)
  • The Protanisoptera, another ancestral group which lacks certain wing vein characters found in modern Odonata, lived from the Early to Late Permian age until the end Permian event, and are known from fossil wings from current day United States, Russia, and Australia, suggesting they might have been cosmopolitan in distribution. (wikipedia.org)
  • genus
  • In 2005 American paleoentomologists David Grimaldi and Michael Engel described a new Sphecomyrminae genus, Sphecomyrmodes based on a fossil found in Burmese amber. (wikipedia.org)
  • earliest
  • Palaeontologists disagree about whether some body fossils from the mid Ordovician, about 472 to 461 million years ago, are the remains of oligochaetes, and the earliest indisputable fossils of the group appear in the Tertiary period, which began 65 million years ago. (wikipedia.org)
  • The earliest sutured trilobite found so far (Lemdadella), occurs almost at the same time as the earliest Olenellina, however, implying that trilobite origin lies before the start of the Atdabanian, but without leaving fossils. (wikipedia.org)
  • thorax
  • Segmentation is usually indistinct, and the body is more or less evenly divided between the head and thorax , with little, if any, abdomen . (wikipedia.org)
  • A fertilised egg hatches into a nauplius: a one-eyed larva comprising a head and a telson , without a thorax or abdomen. (wikipedia.org)
  • The body can be divided into three distinct parts (tagmata) - head, thorax and abdomen. (wikipedia.org)
  • large
  • A large number of other arthropods are preserved in the amber with the ants, including several other hymenopteran families, a dermapteran, an orthopteran, seven dipterans, two arachnids, a myriapod, and a large blattodean. (wikipedia.org)
  • Adult dragonflies are characterized by large, multifaceted eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body. (wikipedia.org)
  • The smooth compound eyes are large and peculiarly well-developed. (wikipedia.org)
  • pous
  • The scientific Latin term octopus was derived from Ancient Greek ὀκτώπους or ὀκτά-, a compound form of ὀκτώ ( oktō , "eight") and πούς ( pous , "foot"), used for example by Alexander of Tralles (c. 525-c. 605) for the common octopus. (wikipedia.org)
  • early
  • they have been considered to represent stem- and crown-group arthropods, stem-group vertebrates, and early deuterostomes. (wikipedia.org)
  • group
  • Segmental composition and homologies of the head of stem-group Euarthropoda have been the foci of recent studies on arthropod origins. (biomedcentral.com)
  • abdomen
  • Their bodies are soft with a segmented abdomen. (wikipedia.org)
  • however, the wings of most dragonflies are held flat and away from the body, while damselflies hold the wings folded at rest, along or above the abdomen. (wikipedia.org)
  • During mating, the male grasps the female at the back of the head or on the prothorax, and the female curls her abdomen under her body to pick up sperm from the male's secondary genitalia at the front of his abdomen, forming the "heart" or "wheel" posture. (wikipedia.org)
  • fungi
  • Opportunistic infection may be caused by microbes ordinarily in contact with the host, such as pathogenic bacteria or fungi in the gastrointestinal or the upper respiratory tract, and they may also result from (otherwise innocuous) microbes acquired from other hosts (as in Clostridium difficile colitis) or from the environment as a result of traumatic introduction (as in surgical wound infections or compound fractures). (wikipedia.org)
  • adult
  • The adult common firecrest has a distinguishing face pattern showing a bright white supercilium (eyebrow) and black eye-stripe, and the juvenile usually shows enough of this face pattern to be readily distinguished from the plain-faced goldcrest. (hitchhikersgui.de)
  • An adult dragonfly's compound eyes have nearly 24,000 ommatidia each. (wikipedia.org)
  • eggs
  • the females deposit eggs on or in a host arthropod on which the larvae then feed. (wikipedia.org)
  • Oligochaetes are full hermaphrodites and produce a ring-like cocoon around their bodies, in which the eggs and hatchlings are nourished until they are ready to emerge. (wikipedia.org)
  • modern
  • Fossils of most modern mobile polychaete groups appeared by the end of the Carboniferous, about 299 million years ago. (wikipedia.org)
  • In addition to stabilising the body while swimming, a quick flick of the tail fan can rapidly propel the animal backwards, which may have functioned as a means of escaping predators like in modern shrimp. (wikipedia.org)
  • bacteria
  • Most of the DNA of the estimated 100 quadrillion cells in our bodies is not "ours," but belongs to cohabiting bacteria. (culanth.org)
  • Ten percent of our dry weight is bacteria, but there are ten of "their" cells in our body for every one of "ours," and we cannot make vitamin K or B12 without them. (culanth.org)
  • characteristic
  • They bear a fringe of long, slender filaments, all of which are directed towards the middle of the body, a characteristic shared by extant crustaceans. (wikipedia.org)
  • enrollment
  • Principal evolutionary trends from primitive morphologies, such as exemplified by Eoredlichia, include the origin of new types of eyes, improvement of enrollment and articulation mechanisms, increased size of pygidium (micropygy to isopygy), and development of extreme spinosity in certain groups. (wikipedia.org)
  • flaps
  • The flaps along its body could probably be moved in a wave-like formation, allowing it to swim quickly or to 'hover', as in Batoidea (rays) or cuttlefish. (wikipedia.org)
  • millimetres
  • So, even though it's only a few millimetres across, it immediately caught my eye. (blogspot.com)
  • Most earwigs are flattened (which allows them to fit inside tight crevices, such as under bark) with an elongated body generally 7-50 millimetres (0.28-1.97 in) long. (wikipedia.org)
  • seen
  • Paleontology portal Origin of claws seen in 390-million-year-old fossil Panda's Thumb: Schinderhannes bartelsi ScienceBlogs: Schinderhannes bartelsi, by PZ Myers showing a cladogram as proposed by G. Kühl et al. (wikipedia.org)
  • groups
  • Using diatom and chrysophyte fossil records, research groups led by Rick Battarbee (UK), Ingemar Renberg (Sweden), Don Charles (US), John Kingston (US), and John Smol (Canada) were able to clearly demonstrate that many northern lakes had rapidly acidified, in parallel with increased industry and emissions. (wikipedia.org)
  • example
  • Torgny Wiederholm and Bill Warwick, for example, used chironomid fossils to assess the impacts of increased nutrient loading (anthropogenic eutrophication) on lake communities. (wikipedia.org)
  • For example, a construct with impregnated pharmaceutical products can be placed into the body, which permits the prolonged release of a drug over an extended period of time. (wikipedia.org)
  • Opportunistic pathogens Opportunistic pathogens can cause an infectious disease in a host with depressed resistance (immunodeficiency) or if they have unusual access to the inside of the body (for example, via trauma). (wikipedia.org)
  • legs
  • Millipedes can be distinguished from the somewhat similar but only distantly related centipedes (class Chilopoda), which move rapidly, are carnivorous, and have only a single pair of legs on each body segment. (wikipedia.org)