• Cambrian
  • 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)
  • 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)
  • 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)
  • In 2011, six fossils of compound eyes dated to the Cambrian period (515 million years ago) were recovered from an archaeological dig at Emu Bay on Kangaroo Island, Australia. (wikipedia.org)
  • Waptia fieldensis is an extinct species of arthropod from the Middle Cambrian Burgess Shale Lagerstätte of Canada. (wikipedia.org)
  • Opabinia regalis is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte of British Columbia, Canada. (wikipedia.org)
  • 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)
  • 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)
  • 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)
  • 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 first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period (521 million years ago), and they flourished throughout the lower Paleozoic era before beginning a drawn-out decline to extinction when, during the Devonian, all trilobite orders except the Proetids died out. (wikipedia.org)
  • Morphological similarities between early trilobites and other Cambrian arthropods (e.g. the Burgess shale fauna and the Maotianshan shales fauna) make analysis of ancestral relationships difficult. (wikipedia.org)
  • However, that trilobites share a common ancestor with other arthropods before the Ediacaran-Cambrian boundary is still reasonable to assume. (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)
  • 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)
  • The small shelly fauna are a very mixed collection of fossils found between the Late Ediacaran and Middle Cambrian periods. (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)
  • Arthropods have remained the dominant component of animal species diversity beginning with their earliest recognition in the Early Cambrian. (blogspot.fr)
  • The first eyes appeared about 543 million years ago - the very beginning of the Cambrian period - in a group of trilobites called the Redlichia. (newscientist.com)
  • Trilobites
  • 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)
  • Trilobites form one of the earliest known groups of arthropods. (wikipedia.org)
  • By the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. (wikipedia.org)
  • Most lifestyles expected of modern marine arthropods are seen in trilobites, with the possible exception of parasitism (where scientific debate continues). (wikipedia.org)
  • The earliest trilobites known from the fossil record are redlichiids and ptychopariid bigotinids dated to some 540 to 520 million years ago. (wikipedia.org)
  • Morphological similarities between trilobites and early arthropod-like creatures such as Spriggina, Parvancorina, and other "trilobitomorphs" of the Ediacaran period of the Precambrian are ambiguous enough to make detailed analysis of their ancestry far from compelling. (wikipedia.org)
  • Evidence suggests that significant diversification had already occurred before trilobites were preserved in the fossil record, easily allowing for the "sudden" appearance of diverse trilobite groups with complex derived characteristics (e.g. eyes). (wikipedia.org)
  • 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)
  • Correctly recognizing the arthropod nature of the fossil, zoologist James DeKay in 1825 assigned its taxonomic classification as Genus Eurypterus and its species designation as remipes, although he thought it was a crustacean. (blogspot.fr)
  • 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)
  • Their apparent dual respiratory system (four pairs of book gills housed within branchial chambers) have led some paleontologists to suggest that eurypterids made forays onto land, an evolutionary transition that many arthropods ultimately made. (blogspot.fr)
  • Arthropods, the phylum to which eurypterids belong, are thought to have evolved from annelids (segmented worms) 500 to 600 million years ago, although several members of the Neoproterozoic Ediacara biota may represent the earliest ancestors. (blogspot.fr)
  • Burgess Shale
  • The first fossils of Anomalocaris were discovered in the Ogygopsis Shale by Joseph Frederick Whiteaves, with more examples found by Charles Doolittle Walcott in the famed Burgess Shale. (wikipedia.org)
  • Based on the number of individuals, Waptia fieldensis is the third most abundant arthropod from the Burgess Shale Formation, with thousands of specimens collected. (wikipedia.org)
  • Waptia fieldensis was one of the first fossils discovered by Charles D. Walcott from the Burgess Shale in August 1909. (wikipedia.org)
  • Charles Doolittle Walcott found in the Burgess Shale nine almost complete fossils of Opabinia regalis and a few of what he classified as Opabinia media, and published a description of all of these in 1912. (wikipedia.org)
  • A re-analysis of fossils from the Burgess Shale lagerstätte increased interest in the issue when it revealed animals, such as Opabinia, which did not fit into any known phylum. (wikipedia.org)
  • 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)
  • 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)
  • And their appearance in the fossil record is strikingly sudden - trilobite ancestors from 544 million years ago don't have eyes. (newscientist.com)
  • eurypterid
  • The eurypterid shown above ( Pterygotus ) has unusually large compound eyes. (berkeley.edu)
  • Jason Dunlop of the University of Manchester has reported finding slit-like structures and book lungs on some eurypterid fossils. (berkeley.edu)
  • He recognized the arthropod nature of the first-ever described eurypterid specimen, found by Dr. S. L. Mitchill. (wikipedia.org)
  • As with the xiphosurans, the eurypterid body can be divided into two primary sections. (wikipedia.org)
  • Jaekelopterus is currently the largest known eurypterid and the largest known arthropod. (wikipedia.org)
  • Eurypterus remipes was eventually designated the official fossil of the State of New York in 1984, an appropriate choice, attributable to its abundance (more than 10,000 specimens have been recovered), and since the majority of productive eurypterid-bearing regions of the world are found within the state's borders. (blogspot.fr)
  • Looking like a mix between a scorpion and a lobster on steroids, the extinct eurypterid (you-RIP-ter-id) or "sea scorpion" was the largest known arthropod, an immense and diverse menagerie of both aquatic and terrestrial invertebrate animals that also includes insects, lobsters, crabs, centipedes, scorpions, spiders and mites. (blogspot.fr)
  • 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)
  • They are segmented animals, united by a common body plan comprising 20 body segments (rarely 21), and divided into a head, thorax, and abdomen. (wikipedia.org)
  • 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)
  • gills
  • The biramous limb of arthropods may then have arisen through fusion of anomalocaridid lateral lobes and gills. (wikipedia.org)
  • 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)
  • phylum
  • When the first thorough examination of Opabinia in 1975 revealed its unusual features, it was thought to be unrelated to any known phylum, although possibly related to a hypothetical ancestor of arthropods and of annelid worms. (wikipedia.org)
  • The idea of body plans originated with vertebrates, which were grouped into one phylum. (wikipedia.org)
  • Insects or Insecta (from Latin insectum ) are hexapod invertebrates and the largest group within the arthropod phylum . (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)
  • Uncommon for chelicerates, horseshoe crabs have two compound eyes. (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)
  • lobes
  • Additional characters conventionally attributed to mushroom bodies include the presence of inhibitory feedback pathways from proximal to more distal levels of the lobes and calyx ( Leitch and Laurent, 1996 ). (elifesciences.org)
  • The body was flanked with a series of flexible swimming lobes. (wikipedia.org)
  • It propelled itself through the water by undulating the flexible lobes on the sides of its body. (wikipedia.org)
  • Each lobe sloped below the one more posterior to it, and this overlapping allowed the lobes on each side of the body to act as a single "fin", maximizing the swimming efficiency. (wikipedia.org)
  • Opabinia was a soft-bodied animal, averaging about 5.7 cm in length (excluding proboscis), and its segmented body had lobes along the sides and a fan-shaped tail. (wikipedia.org)
  • 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)
  • 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)
  • meaning "three lobes") are a fossil group of extinct marine arachnomorph arthropods that form the class Trilobita. (wikipedia.org)
  • primitive
  • Overall, the body structure of Prionomyrmex shows that it is more primitive than Myrmecia. (wikipedia.org)
  • Owing to its body structure, Nothomyrmecia is regarded to be the most primitive ant alive and a 'living fossil', stimulating studies on its morphology, behaviour, ecology, and chromosomes. (wikipedia.org)
  • Fuxianhuia 's body is understandably primitive, which is par for the prehistoric course, given that it lived some 290 million years before the dinosaurs emerged. (scientificamerican.com)
  • 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)
  • Chelicerates
  • Fossil Taxa and Relationships of Chelicerates" pp. 303-311 in G. D. Edgecombe (ed. (berkeley.edu)
  • Chelicerates' bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the prosoma or cephalothorax, and the rear tagma is called the opisthosoma or abdomen. (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)
  • 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)
  • 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 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)
  • 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)
  • 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)
  • Smart, large eyes with good vision. (prezi.com)
  • 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)
  • prosoma
  • The front portion is the prosoma , where the legs are attached and the eyes and mouth are located. (berkeley.edu)
  • The basic body plan of a horseshoe crab consists of three parts: the prosoma, the opisthosoma and the telson. (wikipedia.org)
  • 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)
  • telson
  • There are a few fossils in which part of the intestine is preserved, and this ends in an opening between the final tergite and the telson, on the underside of the tail. (berkeley.edu)
  • A long telson is present at the end of the body. (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)
  • segments
  • 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)
  • 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)
  • Another major group of arthropods, however, called the branchiopods (which includes brine shrimp and Daphnia water fleas ) that emerged later, have much simpler brains with only two optic neuropils that are not connected like those in Fuxianhuia . (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)
  • morphological
  • No previously described crustacean possesses a mushroom body as defined by strict morphological criteria although crustacean centers called hemiellipsoid bodies, which serve functions in sensory integration, have been viewed as evolutionarily convergent with mushroom bodies. (elifesciences.org)
  • The striking morphological similarities of the eyes of Waptia fieldensis to that of extant mysid shrimp make it very likely that they were capable of producing true visual images or were at least sensitive to motion. (wikipedia.org)
  • myriapod
  • The oldest unequivocal myriapod fossil is of the millipede Pneumodesmus newmani, from the late Silurian (428 million years ago). (wikipedia.org)
  • ventral
  • Scientists believe the two ventral eyes aid in the orientation of the horseshoe crab when swimming. (wikipedia.org)
  • evolutionary
  • The study of these fossils has facilitated important contributions to biostratigraphy, paleontology, evolutionary biology, and plate tectonics. (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)
  • 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)
  • 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 fossil is less than one meter long, although this specimen appears to be a juvenile, and it is possible that Bambiraptor is really just a juvenile Saurornitholestes. (wikia.com)
  • 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)
  • 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)
  • 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)
  • 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)