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102-507: (8 more unnamed species) Anomalocaris ("unlike other shrimp", or "abnormal shrimp") is an extinct genus of radiodont , an order of early-diverging stem-group arthropods . It is best known from the type species A. canadensis, found in the Stephen Formation (particularly the Burgess Shale ) of British Columbia , Canada . The other named species A. daleyae is known from the somewhat older Emu Bay Shale of Australia . Other unnamed Anomalocaris species are known from China and

204-594: A holothurian . In 1966, the Geological Survey of Canada began a comprehensive revision of the Burgess Shale fossil record, led by Cambridge University paleontologist Harry B. Whittington . In the process of this revision, Whittington and his students Simon Conway Morris and Derek Briggs would discover the true nature of Anomalocaris and its relatives, but not without contributing to the history of misinterpretations first. In 1978, Conway Morris recognized that

306-804: A horseshoe crab . Bands of setal blades with wrinkling lanceolate blades may have increased the surface area, suggesting they were gills , providing the animal's respiratory function. Abundance of the remains of scleritzed structures such as disarticulated frontal appendages and head sclerite complexes, suggest that mass moulting events may have occurred among radiodonts, a behavior which also has been reported in some other Cambrian arthropods such as trilobites . Radiodonts had diverse feeding strategies, which could be categorized as raptorial predators , sediment sifters, or suspension, filter feeders . For example, raptorial predators like Anomalocaris and Amplectobeluids might have been able to catch agile prey by using their raptorial frontal appendages;

408-618: A hurdiid radiodont in recent analyses, as a species more closely related to euarthropods than other radiodonts (based on some putative euarthropod-like features found on Schinderhannes ). However, neither each of them were supported by later investigations. The radial mouthparts are not cycloneuralian-exclusive and more likely present result of convergent evolution or ecdysozoa n plesimorphy , since they also have been found in panarthropods such as tardigrade and some lobopodia ns; radiodonts lacking definitive euarthropod features such as trunk tergites and multiple head appendages, and

510-816: A 2007 calendar ISBN   0-7649-3622-0 of Knight's paintings is also currently available. Additionally, fantasy artist William Stout has compiled a series of Charles Knight Sketchbooks , which contain many rare and previously unpublished drawings and studies by Knight. Because Knight worked in an era when new and often fragmentary fossils were coming out of the American west in quantity, not all of his creations were based on solid evidence; dinosaurs such as his improbably-adorned Agathaumas (1897) for example, were somewhat speculative. His depictions of better-known ceratopsians as solitary animals inhabiting lush grassy landscapes were largely imaginative (the grasslands that feature in many of his paintings didn't appear until

612-431: A big influence on him. In 2012, a book about Knight and his art written by Richard Milner titled Charles R. Knight The Artist Who Saw Through Time was published. It starts with an introduction by Knight's granddaughter Rhoda. A website dedicated to Knight was created and maintained by Rhoda and features many of his paintings. An homage to the painter was also made in the 1998 IMAX feature film, T-Rex: Back to

714-615: A clade including upper stem (e.g. fuxianhuiids and bivalved arthropods) and crown Euarthropoda (e.g. Artiopoda , Chelicerata and Mandibulata ). This interpretation is supported by numerous arthropod groundplan found on radiodonts and opabiniids, such as stalked compound eyes , digestive glands, trunk appendages forming by dorsal and ventral elements (precursor of arthropod biramous appendages). Compared to opabiniids, which possess posterior mouth opening and fused frontalmost appendages (comparable to euarthropod posterior-facing labrum /hypostome complex), radiodonts on

816-671: A comparable environment; the shallow, tropical waters of Cambrian Australia. The Maotianshan Shale and the Emu Bay Shale are very close in proximity, being separated by a small landmass, far from the Burgess Shale. These two locations also included "Anomalocaris" kunmingensis and "Anomalocaris" briggsi respectively, species that previously attributed but taxonomically unlikely to be a member of Anomalocaris nor even Anomalocarididae. Radiodonta Anomalocarida Radiodonta (also known as radiodonts , radiodontans , radiodontids , anomalocarids , or anomalocaridids , although

918-546: A frequent contributor to National Geographic . He also wrote and illustrated several books of his own, such as Before the Dawn of History (Knight, 1935), Life Through the Ages (1946), Animal Drawing: Anatomy and Action for Artists (1947), and Prehistoric Man: The Great Adventure (1949). Additionally, Knight became a popular lecturer , describing prehistoric life to audiences across the country. Eventually, Knight began to retire from

1020-435: A group of lobopodians that bore robust frontal appendages and digestive glands, but no body flaps. Such intermediate forms between lobopodian and radiodont/euarthropod suggest that the total-group Arthropoda arose from a paraphyletic lobopodian grade, alongside the other two extant panarthropod phyla Tardigrada and Onychophora . Previous studies may suggest radiodonts as a group other than stem-arthropods, such as

1122-399: A head shield, dorsal carapace or H-element, was shaped like a laterally-elongated oval, with a distinct rim on the outer edge. The remaining two lateral sclerites, known as P-elements, were also ovoid, but connected by a bar-like outgrowth. The P-elements were previously misinterpreted as two huge compound eyes. Two large frontal appendage were positioned in front of the mouth, at the front of

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1224-407: A hitherto unknown phylum ; cycloneuralia n worms undergone convergent with arthropods (based on the cycloneuralian-like radial mouthparts); stem chelicerate euarthropods alongside megacheira ns also known as great appendage arthropods (based on the similarity between radiodont frontal appendages, megacheiran great appendages and chelicerae ); or Schinderhannes bartelsi , which resolved as

1326-454: A large diversity of nektonic and pelagic soft-bodied animals. It probably would have not hunted benthic animals like trilobites, considering the possibility of damaging the frontal appendages on the substrate while trying to grab prey from seafloor at speed. Instead, other animals such as other radiodonts (e.g. Hurdia , Cambroraster , Titanokorys , Stanleycaris ) and artiopods (e.g. Sidneyia ) would have been benthic predators in

1428-479: A length of 8.3 cm (3.3 in) An isolated frontal appendage of a hurdiid with a length less than half that of the juvenile Lyrarapax is known, but it is not known whether this specimen pertains to an adult. The largest known Cambrian radiodont was Amplectobelua , reaching lengths of up to 90 cm (35 in) based on an incomplete specimen. Anomalocaris canadensis was also relatively large, estimated up to 34.2–37.8 cm (13.5–14.9 in) long, and

1530-440: A mural featuring Tyrannosaurus and Triceratops . This confrontation scene between a predator and its prey became iconic and inspired a huge number of imitations, establishing these two dinosaurs as "mortal enemies" in the public consciousness . The Field Museum's Alexander Sherman said, "It is so well loved that it has become the standard encounter for portraying the age of dinosaurs". Knight's work also found its way to

1632-443: A nonmineralized cuticle typically most robust in the jaws and claws. The body is subdivided into two tagmata , much like the prosoma and opisthosoma of chelicerate arthropods. Typically, the front part shows no external segmentation, bears one pair of preoral claws, a pair of prominent eyes, and ventral jaws with radiating teeth. Some forms have additional rows of teeth and three or four postoral gnathobasic limb pairs. The trunk

1734-569: A predatory lifestyle. In the case of A. canadensis , its outstanding size amongst Burgess Shale fauna also make it one of the first apex predators known to exist. However, the long-standing idea that Anomalocaris fed on hard-bodied animals, especially its ability to penetrate mineralized exoskeleton of trilobites, has been questioned, with many recent studies considering it more likely that Anomalocaris exclusively hunted soft-bodied prey. Some Cambrian trilobites have been found with round or W-shaped "bite" marks, which were identified as being

1836-516: A revolutionary idea to put entire skeletons of dinosaurs on display. Originally, fossils were kept out of the public's eye and were then stored in store room shelves for study by scientists only. But Osborn had the idea of creating these new exhibits for the public. He assembled a team of himself, Knight, and Dr. William Diller Matthew . Knight sketched the skeletons while Matthew and Osborn mounted them. Cope died shortly after Knight met with him after he became impressed by Knight's sketches. The museum

1938-463: A row, forming bands of gill -like structures known as setal blades, covered the dorsal surface of each body segment. At least in Aegirocassis , each of the lanceolate blades are covered in wrinkles. The ventral flaps may be homologous to the endopod of the biramous limbs of euarthropods and lobopodous limbs (lobopods) of gilled lobopodians , and the dorsal flaps and setal blades may be homologous to

2040-409: A scissor-like slicing or grasping motion. Oral cones of radiodonts may have been used for suction and/or biting. Together with the great variety of frontal appendages in different species of radiodonts, differentiation of oral cones between species suggests preferences of different diets as well. For example, the triradial oral cone of Anomalocaris with irregular, tuberculated toothplates and

2142-944: A small opening may have been adapted to small and nektonic prey, while the rigid tetraradial oral cones of Peytoia , Titanokorys , Hurdia , and one isolated oral cone attributed to Cambroraster with a larger opening and sometimes additional tooth plates may have been capable to consume larger food items relative to their body size and probably benthic or endobenthic prey. Priapulida [REDACTED] and relatives Onychophora [REDACTED] Tardigrada [REDACTED] Lobopodian grade ( paraphyletic ) [REDACTED] Siberiid lobopodians [REDACTED] Pambdelurion [REDACTED] Kerygmachela [REDACTED] Opabiniidae [REDACTED] Radiodonta [REDACTED] Euarthropoda [REDACTED] Most phylogenetic analyses suggest that radiodonts, alongside opabiniids ( Opabinia and Utaurora ), are stem-group arthropods just basal to deuteropoda ,

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2244-412: A tail fan in some species, may have helped steering and/or stabilizing the animal during locomotion. In Anomalocaris , morphology of the tail fan even suggests it could rapidly change its swimming direction efficiently. On the other hand, some hurdiids have features significantly specialized for a nektobenthic lifestyle, such as Cambroraster with its dome-like H-element similar to the carapace of

2346-464: A tale of humor, error, struggle, frustration, and more error, culminating in an extraordinary resolution that brought together bits and pieces of three "phyla" in a single reconstructed creature, the largest and fiercest of Cambrian organisms. Anomalocaris fossils were first collected in 1886 by Richard G. McConnell of the Geological Survey of Canada (GSC). Having been informed of rich fossils at

2448-1013: A typical radial arrangement. Three head sclerite ( carapace ) complex formed by a central H-element (anterior sclerite or head shield) and a pair of P-elements (lateral sclerites) cover the dorsal and laterovental surface of the animal's head. The P-elements may connect to each other as well as the H-element by a narrow anterior extension (P-element neck or 'beak'). The head sclerites are small and ovoid in Anomalocarididae and Amplectobeluidae , but often enlarged in Hurdiidae , corresponded to their distinct body shapes (streamlined in Anomalocarididae/Amplectobeluidae but often compact in Hurdiidae). The head bore two stalked compound eyes , which may have had mobility, and are located between

2550-578: A typical reptile. Knight often restored extinct mammals, birds and marine reptiles in very dynamic action poses, but his depictions of large dinosaurs as ponderous swamp-dwellers destined for extinction reflected more traditional concepts (Paul, 1996). In his catalogue to Life through the Ages (1946), he reiterated views that he had written earlier (Knight, 1935), describing the great beasts as "slow-moving dunces" that were "unadaptable and unprogressive" while conceding that small dinosaurs had been more active. Some of his pictures are now known to be wrong, such as

2652-749: Is metameric , typically with about 13 segments laterally developing imbricating lobes for swimming and gills for respiration, and may end in a prominent three-part tail. Some forms have gnathobasic trunk limbs. In 2014, the clade Radiodonta was defined phylogenetically as a clade including any taxa closer to Anomalocaris canadensis than Paralithodes camtschaticus . In 2019, it was redefined morphologically as animal bearing head carapace complex with central (H-) and lateral (P-) elements; outgrowths (endites) from frontal appendages bearing auxiliary spines; and reduced anterior flaps or bands of lamellae (setal blades) and strong tapering of body from anterior to posterior. Most radiodonts were significantly larger than

2754-465: Is composed of multiple body segments, each associated with pairs of flaps and gill-like structures (setal blades). The anterior structures on the head are a pair of frontal appendages which have been referred to as 'claws', 'grasping appendages', 'feeding appendages', or 'great appendages' in previous studies (the last term is discouraged since the homology between frontal appendages and the original, morphologically distinct megacheiran great appendages

2856-692: Is known to have pediform trunk appendages (legs). The trunk has numerous body segments ( somites ), tapering from anterior to posterior, with the anterior three or four segments significantly constricted into a neck region. The trunk appendages were fin-like body flaps ('lateral flaps' or 'lobes' in some studies), usually one pair of ventral flaps per body segment, each slightly overlapping the one more anterior to it, but additional, non-overlapping sets of small dorsal flaps may occur in some Hurdiid species. The flaps may have numerous vein-like structures (referred to as 'strengthening rays', 'flap rays', 'tranverse rods', 'transverse lines' or 'veins' ). The flaps on

2958-408: Is larger than A. canadensis , with the largest known appendage measuring up to 18.3 cm (7.2 in) long, which would have belonged to an individual between 34.8–51.2 cm (1.14–1.68 ft) long. Anomalocaris propelled itself through the water by undulating the flexible flaps on the sides of its body. Each flap sloped below the one more posterior to it, and this overlapping allowed

3060-620: Is more capable to prey on smaller (2–5 cm in diameter), active, soft-bodied animals (e.g. vetulicolian ; free-swimming arthropods like isoxyids and hymenocarines ; Nectocaris ). Bicknell et al. (2023) examined the frontal appendages of Anomalocaris , suggesting it was an active nektonic apex predator. Postured with the frontal appendages outstretched, Anomalocaris would have been able to swim with maximized speed, similar to modern predatory water bugs . Its eyes would be suitable to hunt prey in well-lit waters. Anomalocaris would have hunted various free-swimming animals since there are

3162-531: Is questionable. ). They are sclerotized (hardened) and arthropodized (segmented), bearing ventral endites (spines) on most of their podomeres (segmental units), and the endites may bear additional rows of auxiliary spines on their anterior and posterior margins. The frontal appendage consists of two regions: the shaft ('peduncle', 'base' or 'promixal region' in some studies) and the distal articulated region (also referred to as 'claw' ). A triangular region covered by soft cuticle (arthrodial membrane) may occur on

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3264-741: The Carnegie Museums in Pittsburgh , the Smithsonian Institution , and Yale's Peabody Museum of Natural History , among others. Knight also created sculptures of animals both living and extinct. Several zoos , such as the Bronx Zoo , the Lincoln Park Zoo , and the Brookfield Zoo , also approached Knight to paint murals of their living animals, and Knight enthusiastically complied. Knight

3366-471: The Cenozoic ). Although Knight sometimes made musculoskeletal studies of living animals, he did not do so for his dinosaur restorations, and he restored many dinosaurs with typical reptilian-like limbs and narrow hips (Paul, 1996). In the 1920s, studies by the celebrated palaeontologists Alfred Romer and Gerhard Heilmann (Heilmann, 1926) had confirmed that dinosaurs had broad avian-like hips rather than those of

3468-520: The Early Devonian member Schinderhannes bartelsi from Germany. The name Radiodonta (Latin for radius "spoke of a wheel" and Greek for odoús "tooth") refers to the radial arrangement of tooth plates (oral cone) surrounding the mouth, although these features are suggested to be absent in some radiodont species. The original diagnosis of order Radiodonta in 1996 is as follows: Radiodontids are bilaterally symmetrical, elongate arthropods with

3570-538: The Natural History Museum of Los Angeles County which portrayed some of the birds and mammals whose remains had been found in the nearby La Brea Tar Pits . The following year, Knight began a 28- mural series for Chicago 's Field Museum of Natural History , a project which chronicled the history of life on earth and took four years to complete. At the Field Museum, he produced one of his best-known pieces,

3672-585: The Stephen Formation in British Columbia, McConnell climbed Mount Stephen on 13 September 1886. He found abundant trilobites, along with two unknown specimens. In August 1891, Henri-Marc Ami , Assistant Palaeontologist at GSC, collected many trilobites and brachiopod fossils, along with 48 more of the unknown specimens. The fifty specimens were examined and described in 1892 by GSC paleontologist Joseph Frederick Whiteaves . Whiteaves interpreted them as

3774-586: The United States . Like other radiodonts, Anomalocaris had swimming flaps running along its body, large compound eyes , and a single pair of segmented, frontal appendages , which in Anomalocaris were used to grasp prey. Estimated to reach 34.2–37.8 cm (13.5–14.9 in) long excluding the frontal appendages and tail fan, Anomalocaris is one of the largest animals of the Cambrian, and thought to be one of

3876-567: The Woolly Mammoth . All of these have been reproduced in numerous places and have inspired many imitations. Knight's work for the museum was not without critics, however. Although he spent considerable time at zoos studying the movements and habits of living animals, many curators argued that his work was more artistic than scientific, and protested that he did not have sufficient scientific expertise to render prehistoric animals as precisely as he did. While Knight himself agreed that his murals for

3978-488: The American Museum of Natural History is 1897's Leaping Laelaps , which was one of the few pre-1960s images to present dinosaurs as active, fast-moving creatures (thus anticipating the " Dinosaur Renaissance " theories of modern paleontologists like Robert Bakker ). Other familiar American Museum paintings include Knight's portrayals of Agathaumas , Allosaurus , Apatosaurus , Brontosaurus , Smilodon , and

4080-556: The Burgess Shale in relatively great numbers. In the Burgess Shale, Anomalocaris is more common in the older sections, notably the Mount Stephen trilobite beds . However, in the younger sections, such as the Phyllopod bed , Anomalocaris could reach much greater sizes—roughly twice the size of its older, trilobite bed relatives. These rare giant specimens have previously been referred to a separate species, Anomalocaris gigantea ; however,

4182-702: The Burgess Shale. Specimens of Anomalocaris have been found worldwide spanning from Cambrian Stage 3 to the Guzhangian . Aside from the Burgess Shale and Emu Bay Shale, fossils have been found in the Chengjiang Biota , Hongjingshao Formation , Balang Formation and the Kaili Formation of China, as well as the Eagar Formation and Weeks Formation in the United States. Anomalocaris canadensis lived in

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4284-402: The Cambrian hurdiid Titanokorys approached around 50 cm (20 in) long. The body of a radiodont could be divided into two regions: head and trunk. The head is composed of only one body segment known as the ocular somite, covered by sclerites (head carapace complex), bore arthropodized frontal appendages, ventral mouthparts (oral cone), and stalked compound eyes . The tapering trunk

4386-555: The Hall of the Age of Man were "primarily a work of art," he insisted that he had as much paleontological knowledge as the museum's own curators. In 1900, Knight married Annie Humphrey Hardcastle and had a daughter named Lucy. After Knight established a reputation at the American Museum of Natural History, other natural history museums began requesting paintings for their own fossil exhibits. In 1925, for example, Knight produced an elaborate mural for

4488-433: The L.A. County Museum I vividly remember a beautiful Knight mural on one of the walls depicting the way the tar pits would have looked in ancient times. This, plus a picture book about Knight's work my mother gave me, were my first encounters with a man who was to prove an enormous help when the time came for me to make three-dimensional models of these extinct beings". Paleoartist Gregory S. Paul has also mentioned Knight as

4590-400: The abdomens of phyllocarid crustaceans , and gave the full scientific name Anomalocaris canadensis . He describes the crustacean characters: Body or abdominal segments, which, in all the specimens collected, are abnormally flattened laterally, a little higher or deeper than long, broader above than below, the pair of ventral appendages proceeding from each, nearly equal in height or depth to

4692-404: The armour of trilobites. A. canadensis was suggested to have been capable of feeding on organisms with hard exoskeletons due to the short, robust spines on its frontal appendages. However, this conclusion is solely based on the comparison with the fragile frontal appendages of suspension feeding radiodonts (e.g. Echidnacaris and Houcaris spp.). The typical lack of damage to the endites on

4794-474: The arthropod stem lineage. The constricted neck region with feeding appendicular structures of some radiodont may also shed light on the origin of the sophisticated arthropod head, which was formed by the fusion of multiple anterior body segments. Basal deuteropods that possess a mixture of radiodont/opabiniid characters like Kylinxia and Erratus , may represent intermediate forms between radiodonts, opabiniids and other euarthropods. Taxa just basal to

4896-458: The brain composed of only one brain segment originating from the ocular somite, the protocerebrum. The nerves of the frontal appendages and compound eyes arose from the anterior and lateral regions of the brain. Based on Moysiuk & Caron 2022, the frontal appendage nerves arose from the ventral deutocerebrum, the second brain segment. The previous "frontal appendage nerves" actually represent median eye nerve. In both interpretations, posterior to

4998-459: The brain was a pair of apparently unfused ventral nerve cords which ran through the animal's neck region. Radiodonts were interpreted as nektonic or nektobenthic animals, with their morphology suggesting an active swimming lifestyle. The muscular, overlapping ventral flaps may have propelled the animal through the water, possibly by moving in a wave-like formation resembling modern rays and cuttlefish . Pairs of dorsal flaps, which make up

5100-433: The constricted neck region. It is difficult to distinguish lobes near the tail, making an accurate count difficult. For the main trunk flaps, the type species A. canadensis had 13 pairs. Anomalocaris had an unusual disk-like mouth known as oral cone. The oral cone was composed of several plates organized triradially. Three of the plates were quite large. Three to four medium sized plates could be found between each of

5202-413: The continuously juxtaposed Peytoia , Laggania and frontal appendages ( Anomalocaris and "appendage F") actually represented a single group of enormous creatures. The two genera have now been placed into the order Radiodonta and are commonly known as radiodonts or anomalocaridids. Since Peytoia was named first, it is the accepted correct name for the entire animal. However, the original frontal appendage

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5304-536: The corrections done in 1996 and 2012. It is the type genus of Anomalocarididae , a family which previously included all radiodonts but recently only Anomalocaris and a few closely-related taxa. From the start, Anomalocaris fossil was misidentified, followed by a series of misidentifications and taxonomic revisions. As Stephen Jay Gould , who popularised the Cambrian explosion in his 1989 book Wonderful Life , appropriately described: [The story of Anomalocaris is]

5406-486: The cover of his 1991 book Bully for Brontosaurus and another in his 1996 book Dinosaur in a Haystack . Though many other paleoartists have equaled Knight (perhaps Zdeněk Burian ) Knight's paintings still remain very popular among dinosaur and paleontology enthusiasts. A commemorative edition of Knight's 1946 book Life Through the Ages ISBN   0-253-33928-6 was recently published by Indiana University Press , and

5508-752: The creature with the former name. Gould writes in his 1989 book Wonderful Life , "Not since the Lord himself showed his stuff to Ezekiel in the valley of dry bones had anyone shown such grace and skill in the reconstruction of animals from disarticulated skeletons. Charles R. Knight, the most celebrated of artists in the reanimation of fossils, painted all the canonical figures of dinosaurs that fire our fear and imagination to this day". Other admirers have included special effects artist Ray Harryhausen , who writes in his autobiography An Animated Life , "Long before Obie ( Willis O'Brien ), myself, and Steven Spielberg , he put flesh on creatures that no human had ever seen. […] At

5610-496: The earliest examples of an apex predator , though others have been found in older Cambrian lagerstätten deposits. Since the original description in late 19th century, the frontal appendages were the only known fossilized parts and misidentified as the body parts of other animals. Its radiodont affinity was revealed in 1980s, specifically in a 1985 journal article by Harry B. Whittington and Derek Briggs . The trunk and mouth were reconstructed after another radiodont genus until

5712-490: The earliest large predators, but they also included sediment sifters and filter feeders. Some of the most famous species of radiodonts are the Cambrian taxa Anomalocaris canadensis , Hurdia victoria , Peytoia nathorsti , Titanokorys gainesi , Cambroraster falcatus and Amplectobelua symbrachiata . The later surviving members include the subfamily Aegirocassisinae from the Early Ordovician of Morocco and

5814-526: The endites. The tail was a large tail fan, composed of three pairs of large, lateral fin-shaped lobes and one terminal lobe-like tailpiece. Previous studies suggest the tail fan was used to propel it through Cambrian waters, while further hydrodynamic study rather suggest it was more adapted to provide steering function. The gills of the animal, in the form of long, thin, hair-like structures known as lanceolate blades, were arranged in rows forming setal blades. The setal blades were attached by their margin to

5916-427: The evolution of jointed legs or hardened exoskeletons. This specimen was later identified as that of a new species of Anomalocaris , A. daleyae . Numerous species have been previously referred to Anomalocaris , but subsequent analyses have doubted this generic assignment, and reclassified them within different genera. In 2021, " A. " saron and " A. " magnabasis were reassigned to the new genus Houcaris in

6018-415: The exite and gill-bearing dorsal flaps of the former taxa. The trunk may end either with a tail fan compose of 1 to 3 pairs of blades, a pair of long furcae, an elongated terminal structure, or a featureless blunt tip. Traces of muscles , digestive system and nervous system were described from some radiodont fossils. Pairs of well-developed muscles were connected to the ventral flaps located at

6120-518: The family Tamisiocarididae in 2023. For the time in which it lived, Anomalocaris was gigantic. A complete specimen of A. canadensis , ROMIP 51211, is measured up to 20.5 cm (8.1 in) long (17.4 cm (6.9 in) long when excluding the frontal appendages and tail fan). The largest frontal appendage is measured up to 18 cm (7.1 in) long when extended, and this specimen of A. canadensis would have reached up to 34.2–37.8 cm (1.12–1.24 ft) in body length excluding

6222-403: The family Tamisiocarididae , but subsequent analysis suggests that H. saron is a member of the family Amplectobeluidae instead and that H ? magnabasis (recovered as a sister taxon of Amplectobeluidae) does not form a monophyletic clade with other species of Houcaris . In the same year, " A. " pennsylvanica was reassigned to the genus Lenisicaris . In 2022, specimen ELRC 20001 that

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6324-411: The feeding appendage of similar animal, referred to as "appendage F". Later, while clearing what he thought was an unrelated specimen, Harry B. Whittington removed a layer of covering stone to discover the unequivocally connected frontal appendage identical to Anomalocaris and mouthpart similar to Peytoia . Whittington linked the two species, but it took several more years for researchers to realize that

6426-463: The frontal appendages and tail fan. Previous body length estimation up to 1 m (3.3 ft) is unlikely based on the ratio of body parts (body length measured only about 2 times the length of frontal appendage in A. canadensis ) and the size of largest frontal appendage. A. daleyae (formerly A.  cf. canadensis or A.  aff. canadensis ) from the Emu Bay Shale of Australia

6528-535: The frontal appendages of A. canadensis (with damage only present on a single specimen) suggests that they were not used to grasp hard-shelled prey. As opposed to Peytoia whose oral cone is more rectangular with short protruding spines, the oral cone of A. canadensis has a smaller and more irregular opening, not permitting strong biting motions, and indicating a suction-feeding behavior to suck in softer organisms. Three-dimensional modelling of various radiodont frontal appendages also suggest that A. canadensis

6630-417: The gaps formed by the posterior regions of the H-element and P-elements. The compound eyes of Echidnacaris are exceptionally unstalked. Some species possess an additional median eye behind the H-element. Contrary to the original diagnosis, the division of body segments (segmental boundaries) can be visible externally and no known member of Radiodonta (except the putative radiodont Cucumericrus )

6732-543: The great popularizers of the prehistoric past", and as having influenced generations of museum-goers. Examples of Knight's work frequently appeared in dinosaur books published in the US during the first half of the twentieth century and countless other artists and illustrators borrowed heavily from Knight's conceptions of dinosaurs and other prehistoric animals. More recent works also include examples of Knight's paintings; for example, Stephen Jay Gould used one of Knight's paintings for

6834-409: The hard, calcified exoskeleton of trilobites. Rather, the coprolites may have been produced by different organisms, such as the trilobites of the genus Redlichia . Another suggested possibility was that Anomalocaris fed by grabbing one end of their prey in its oral cone while using its frontal appendages to quickly rock the other end of the animal back and forth. This produced stresses that exploited

6936-422: The head. Each frontal appendage of Anomalocaris usually had 14 podomeres (segmental units, at least 1 for shaft and 13 for distal articulated region), with each appendage being laterally-flattened (taller than wide). Most podomeres were tipped with a pair of endites (ventral spines). The endites themselves were both equipped with multiple auxiliary spines, which branches off from the anterior and posterior margin of

7038-418: The large plates, and several small plates between them. Most of the plates wrinkled and have scale-like tubercles near the mouth opening. Such an oral cone is very different from those of a typical hurdiid radiodont like Peytoia and Hurdia , which is smooth and tetraradial. As a shared character across radiodonts, Anomalocaris also had three sclerites on the top and side of its head. The top one, known as

7140-441: 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. ) is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and were used for a variety of functions. Radiodonts were among

7242-470: The lateral cavities of each body segment. Between the lateral muscles is a sophisticated digestive system, formed by a widening of the foregut and hindgut, both connected by a narrow midgut associated with six pairs of gut divercula (digestive glands). The brain of radiodonts was simpler than the three-segmented (compose of pro-, deuto- and tritocerebrum) brains of euarthropods , but further interpretations differ between studies. Based on Cong et al. 2014,

7344-432: The latter even bore a robust endite for holding prey like a pincer . With the smaller head carapace complex and large surface of arthrodial membranes, frontal appendages of these taxa had greater flexibility. Stout frontal appendages of sediment sifters like Hurdia and Peytoia have serrated endites with mesial curvature, which could form a basket-like trap for raking through sediment and passing food items towards

7446-430: The lobes on each side of the body to act as a single "fin", maximizing the swimming efficiency. The construction of a remote-controlled model showed this mode of swimming to be intrinsically stable, implying that Anomalocaris would not have needed a complex brain to manage balance while swimming. The body was widest between the third and fifth lobe and narrowed towards the tail, with additional three pairs of small flaps on

7548-1028: The megacheiran great appendages were considered to be deutocerebral, which could be non-homologous to the radiodont protocerebral frontal appendages; putative euarthropod characters found on the single Schinderhannes fossil is questionable and may present other radiodont-like structures. Caryosyntrips [REDACTED] Houcaris saron [REDACTED] "Anomalocaris" briggsi [REDACTED] Tamisiocaris [REDACTED] Laminacaris [REDACTED] Houcaris magnabasis [REDACTED] Anomalocaris [REDACTED] Lyrarapax [REDACTED] Amplectobelua [REDACTED] "Anomalocaris" kunmingensis [REDACTED] Ramskoeldia consimilis [REDACTED] Ramskoeldia platyacantha [REDACTED] Paranomalocaris [REDACTED] Peytoia [REDACTED] cf. Peytoia [REDACTED] Stanleycaris [REDACTED] Schinderhannes [REDACTED] Aegirocassis [REDACTED] Charles R. Knight Knight

7650-413: The morphology of the frontal appendages, especially those of the spines, always differs between species, it is one of the most important means of species identification. In fact, many radiodonts are only known from a handful of fossilized frontal appendages. The mouth is on the ventral side of the head, behind the attachment point of frontal appendages and is surrounded by a ring of tooth plates, forming

7752-508: The mouthpart known as oral cone ('jaws' in previous studies ). 3 or 4 tooth plates might be enlarged, giving the oral cone a triradial (e.g. Anomalocaris , Echidnacaris ) or tetraradial (e.g. Hurdiidae , Lyrarapax ) appearance. The inner margin of tooth plates have spikes facing towards the mouth opening. Additional rows of internal tooth plates may occur in some hurdiid genera. Detail reconstruction of some amplectobeluid oral cones are speculative, but they possibly did not present

7854-399: The mouthparts of Laggania were identical to Peytoia , but concluded that Laggania was a composite fossil made up of Peytoia and the sponge Corralio undulata . In 1979, Briggs recognized that the fossils of Anomalocaris were appendages, not abdomens, and proposed that they were the walking legs of a giant arthropod, and that the feeding appendage Walcott had assigned to Sidneyia was

7956-399: The neck region (referred to as 'reduced flaps', 'neck flaps', 'head flaps', 'anterior flaps' or 'differentiated flaps' ) are significantly reduced. In some species, jaw-like feeding appendages called gnathobase-like structures (GLSs) arose from each of the bases of their reduced neck flaps. Numerous elongated blade-like extensions (referred to as lanceolate blades or lamellae ) arranged in

8058-454: The other Cambrian fauna, with typical body lengths of large taxa varying from 30 to 50 cm (12 to 20 in). The largest described radiodont is the Early Ordovician species Aegirocassis benmoulai , which may have grown up to 2 m (6.6 ft) long. A nearly complete specimen of a juvenile Lyrarapax unguispinus measured only 18 mm (0.71 in), making it among the smallest radiodont specimens known, though adults reached

8160-404: The other hand featured euarthropod-like dorsal sclerite (H-element) and arthropodization (frontal appendages) on their head regions, alongside cuticularized gut termini. The fact that both radiodonts and opabiniids lack exoskeleton on their trunk region suggests that the origin of compound eyes and arthropodization (segmented appendages) precede arthrodization (full set of trunk exoskeleton) in

8262-775: The public sphere to spend more time with his grandchildren, mostly his granddaughter Rhoda, who shared his passion for animals and prehistoric life. In his later years, his eyesight began to deteriorate and he painted less often. From 1944 to 1946 he painted his final series of paintings at the National History Museum of Los Angeles County. In 1951, he painted his last work, a mural for the Everhart Museum in Scranton, Pennsylvania . Two years later, on April 15, 1953, Knight died in New York City . Knight has been hailed as "one of

8364-613: The radiodont, opabiniid and euarthropod branch are ' gilled lobopodians ' like Pambdelurion and Kerygmachela , which occasionally united under the class Dinocaridida with opabibiids and radiodonts. They have body flaps, digestive glands, large (presumely compound) eyes and specialized frontal appendages like the former taxa, but their frontal appendages are not arthropodized nor fused, eyes sessile, gill-like structures less prominent, and certainly bore lobopod underneath each of their flaps. Taxa even basal to 'gilled lobopodians' are siberiids like Megadictyon and Jianshanopodia ,

8466-471: The resolution of the 3-centimetre-wide (1.2 in) eyes would have been rivalled only by that of the modern dragonfly , which has 28,000 lenses in each eye. Additionally, estimation of ecdysozoan opsins suggest that Anomalocaris may have had dichromatic color vision . The interpretation of Anomalocaris as an active predator is widely accepted throughout the history of research, as its raptorial frontal appendages and mid-gut glands strongly suggest

8568-508: The rest of his life. At the age of twelve, he enrolled at the Metropolitan Art School to become a commercial artist . In 1890, he was hired by church-decorating firm J. & R. Lamb to design stained-glass windows , and after two years with them, became a freelance illustrator for children's books and magazines , specializing in nature scenes. At this time, he met people like Rudyard Kipling and Arthur Conan Doyle . When Knight

8670-439: The same shape as the mouthparts of Peytoia (previously misidentified as those of Anomalocaris ). Stronger evidence that Anomalocaris ate trilobites comes from coprolite , which contain trilobite parts and are so large that the radiodonts are the only known organism from that period large enough to have produced them. However, since Anomalocaris lacks any mineralized tissue, it seemed unlikely that it would be able to penetrate

8772-420: The segment itself... The generic name Anomalocaris (from ανώμαλος , unlike,— καρίς , a shrimp, i.e. , unlike other other shrimps) [the species name referring to Canada] is suggested by the unusual shape of the uropods or ventral appendages of the body segments and the relative position of the caudal spine. In 1928, Danish paleontologist Kai Henriksen proposed that Tuzoia , a Burgess Shale arthropod which

8874-443: The top side of the animal, two setal blades per body segment. A divide ran down the middle, separating the gills. Based on fossilized eyes from the Emu Bay Shale , which belong to the species Anomalocaris daleyae, the stalked eyes of Anomalocaris were 30 times more powerful than those of trilobites, long thought to have had the most advanced eyes of any contemporary species. With one specimen having over 24,000 lenses in one eye,

8976-497: The tripod kangaroo-like posture of the hadrosaurs and theropods , whereas their spinal column was roughly horizontal at the hip; and the sauropods standing deeply in water whereas they were land-dwellers. Knight also drew dinosaur tails dragging on the ground, whereas they were held out approximately horizontally. The late Stephen Jay Gould was one of Knight's most well-known fans, notably refusing to refer to Brontosaurus as " Apatosaurus " because Knight had always referred to

9078-463: The validity of this species has been called into question, and is currently synonymized to A. canadensis . Other unnamed species of Anomalocaris live in vastly different environments. For example, Anomalocaris cf. canadensis (JS-1880) lived in the Maotianshan Shales , a shallow tropical sea or river delta in what is now modern China. Anomalocaris daleyae (Emu Bay Shale) lived in

9180-477: The ventral side between podomeres and provide flexibility. Their purported pre-ocular and protocerebral origin suggest they are homologous to the primary antennae of Onychophora and the labrum of Euarthropoda (all arose from ocular somite ), while subsequent studies also suggest a deutocerebral origin and homologous with the chelicerae of Chelicerata and the antennae or ' great appendages ' of other arthropods (all arose from post-ocular somite 1). Since

9282-573: The weaknesses of arthropod cuticles , causing the prey's exoskeleton to rupture and allowing the predator to access its innards. This behaviour was originally thought to have provided an evolutionary pressure for trilobites to roll up, to avoid being flexed until they snapped. The lack of wear on radiodont mouthparts suggests they did not come into regular contact with mineralized trilobite shells, and were possibly better suited to feeding on smaller, soft-bodied organisms by suction, since they would have experienced structural failure if they were used against

9384-489: The well-developed oral cone. Endites of frontal appendages from suspension/filter feeders like Tamisiocaris and Aegirocassis have flexible, densely-packed auxiliary spines, which could filter out organic components such as mesozooplankton and phytoplankton down to 0.5mm. Frontal appendages of Caryosyntrips , which are unusual for radiodonts in having the direction of endite-bearing surfaces opposing one another and may have been able to manipulate and crush prey in

9486-488: Was actually the only person in America allowed to paint Su Lin , a giant panda that lived at Brookfield Zoo during the 1930s. Although Knight's interest in animals and animal anatomy is well known, Knight also had an interest in botany . He often traveled to Florida and used the palm trees for his prehistoric paintings. While making murals for museums and zoos, Knight continued illustrating books and magazines, and became

9588-470: Was amazed by his watercolor paintings and the successful exhibits. J. P. Morgan (the famous banker), who was a patron to the museum, helped finance the restorations of prehistoric life. His paintings were hugely popular among visitors, and Knight continued to work with the museum until the late 1930s, painting what would become some of the world's most iconic images of dinosaurs, prehistoric mammals, and prehistoric humans. One of Knight's best-known pieces for

9690-406: Was around five or six years old. In later years he abandoned the practice of drawing from books altogether, and instead drew from life. Though legally blind because of astigmatism he inherited from his father and after his right eye was struck by a rock by a playmate, Knight pursued his artistic talents with the help of specially designed glasses which he used to paint inches from the canvas for

9792-526: Was born in Brooklyn , New York City on October 21, 1874. As a child, Knight was deeply interested in nature and animals, largely thanks to his father's passion for the outdoors and spent many hours copying the illustrations from his father's natural history books. His father also took him on trips to the American Museum of Natural History which fueled his knowledge for nature. Knight began drawing when he

9894-422: Was discovered by Charles Doolittle Walcott , who mistook it for a jellyfish and placed it in the genus Peytoia . Walcott also discovered a frontal appendage but failed to realize the similarities to Whiteaves' discovery and instead identified it as feeding appendage or tail of the coexisted Sidneyia . In the same publication in which he named Peytoia , Walcott named Laggania , a taxon that he interpreted as

9996-450: Was eighteen, his father died and he took the little money his father left him and left home. In his free time, Knight visited the American Museum of Natural History, attracting the attention of Dr. Jacob Wortman, who asked Knight to paint a restoration of an extinct hoofed mammal, Elotherium , whose fossilized bones were on display. Knight applied his knowledge of modern pig anatomy , and used his imagination to fill in any gaps. Wortman

10098-413: Was from a larger species distinct from Peytoia and " Laggania " and therefore retains the name Anomalocaris . In 2011, compound eyes of Anomalocaris were recovered from a paleontological dig at Emu Bay Shale on Kangaroo Island , Australia, proving that Anomalocaris was indeed an arthropod as had been suspected. The find also indicated that advanced arthropod eyes had evolved very early, before

10200-400: Was known only from the carapace, represented the missing front half of Anomalocaris . The artists Elie Cheverlange and Charles R. Knight followed this interpretation in their depictions of Anomalocaris . Not known to scientists at the time, the body parts of relatives of Anomalocaris had already been described but not recognized as such. The first fossilized mouth of such a kind of animal

10302-430: Was thrilled with the final result, and the museum soon commissioned Knight to produce an entire series of watercolors to grace their fossil halls. After a tour of Europe by visiting many museums and zoos, Knight returned home where he met two key people in the history of paleontology , Edward Drinker Cope and Henry Fairfield Osborn . Osborn then created the new Department of Vertebrate Paleontology at AMNH and he had

10404-425: Was treated as an unnamed species of Anomalocaris or whole-body specimen of A. saron got a new genus, Innovatiocaris . In 2023, "A". kunmingensis was reassigned to the new genus Guanshancaris in the family Amplectobeluidae . Multiple phylogenetic analyses also suggested that "A". briggsi (tamisiocaridid) was not a species of Anomalocaris either, and it was reassigned to the genus Echidnacaris in

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