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The armoured dinosaur Polacanthus foxi from the Lower Cretaceous of the Isle of Wight

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... It is, however, known from fragmentary remains, primarily the partial holotype skeleton (Mantell, 1833;Pereda-Suberbiola, 1993). By contrast, various specimens have been referred to Polacanthus foxii including several individuals from the Wessex Formation (Barremian) of the Isle of Wight, U.K., and from the Arcillas de Morella and Golmayo formations of Spain (Blows, 1987;Pereda-Suberbiola, 1993;Pereda-Suberbiola et al., 2007;Gasulla et al., 2011), as well as the Lower Greensand of the Isle of Wight (Blows, 2015). In combination, this material represents much of the skeleton, including partial skulls that have been attributed to the taxon (Norman and Faiers, 1996). ...
... Remarks-The combination of vertebrae in the synsacrum (character 1 of Pereda-Suberbiola et al. [2007]) varies intraspecifically, and possibly ontogenetically, within ankylosaurs (Arbour and Currie, 2013a), and the use of isolated osteoderms for diagnoses (character 5 of Pereda-Suberbiola et al. [2007]) is problematic for taxonomy given their variable morphology and the dearth of comparative specimens with armor preserved in situ; it is currently unknown whether isolated osteoderms vary intraspecifically, sexually, or with ontogeny in ankylosaurs. Additionally, the holotype of Polacanthus does not preserve a scapula (character 2 of Pereda-Suberbiola et al. [2007]) and thus this character cannot be autapomorphic for the taxon; this character was presumably included in previous diagnoses as a result of the suggested synonymy of Hoplitosaurus with Polacanthus (Blows, 1987;Pereda-Suberbiola, 1994), although this synonymy is not currently accepted (e.g., Thompson et al., 2012;Arbour and Currie, 2016). ...
... These articles attributed the name to Richard Owen, but there is no previous mention of Polacanthus in any publication by Owen, and moreover, Owen had apparently wanted to call the specimen 'Eucanthus vectianus', although this name was never formally published (Blows, 1983). It has been suggested that the author of the anonymous articles was William Fox, who discovered the specimen (Blows, 1987;Pereda-Suberbiola, 1994) and wanted to name the taxon after himself but could not do so due to professional etiquette; however, there is no proof for this speculation. The name Polacanthus was mentioned in a presentation by Fox at the British Association for the Advancement of Science in 1865, with an abstract published a year later (Fox, 1866); these also attributed the name to Owen. ...
Article
Ankylosaurs, dinosaurs possessing extensive body armor, were significant components of terrestrial ecosystems from the Middle Jurassic–latest Cretaceous. They diversified during the Early Cretaceous, becoming globally widespread. The Lower Cretaceous Wealden Supergroup (Berriasian–Aptian) of Britain has produced abundant ankylosaur material, with three currently recognized taxa: Hylaeosaurus armatus (Grinstead Clay Formation, West Sussex); Polacanthus foxii (Wessex Formation, Isle of Wight); and Horshamosaurus rudgwickensis (Weald Clay Group, West Sussex). However, these taxa are poorly understood; the initial descriptions of Hylaeosaurus and Polacanthus date from the 1800s and subsequent referrals of specimens have been based largely on provenance rather than morphological comparisons. This has led to uncertainty over the definitions of these taxa and the compositions of their hypodigms. Here, we redescribe the holotypes of Hylaeosaurus and Polacanthus, provide comparisons between these taxa, and use this information to assess the taxonomy of all ankylosaur specimens from the British Wealden Supergroup. We conclude that Hylaeosaurus and Polacanthus are valid, distinct taxa, which can be diagnosed by a combination of autapomorphies and a unique combination of characters. However, in both cases, we restrict their hypodigms to the holotypes. ‘Horshamosaurus rudgwickensis’ is a nomen dubium (an indeterminate nodosaurid dinosaur) and the majority of ankylosaur specimens from the Wealden Supergroup are taxonomically indeterminate. Hylaeosaurus and Polacanthus are separated stratigraphically, with Hylaeosaurus from the Valanginian of the Weald Sub-basin and Polacanthus from the Barremian of the Wessex Sub-basin. This separation supports the hypothesis of distinct lower and upper dinosaur faunas in the Wealden Supergroup of Britain.
... As in the polacanthids Mymoorapelta and Hoplitosaurus the ribs are triangular in cross section; however, this occurs only distally in the rib shaft of Gargoy- leosaurus (GILMORE 1914, KIRKLAND & CARPENTER 1994. Proximally the dorsal ribs are T-shaped, with flanges projecting both anteriorly and posteriorly from the shaft, or L-shaped, with a single flange projecting posterior to the shaft; this is also the case for Polacanthus, and many other ankylosaurs (EATON 1960, COOMBS 1978, BLOWS 1987, KIRKLAND & CARPENTER 1994. Distally the flanges taper, eventually merging with the rib shaft. ...
... The anatomical position of the tendons is difficult to determine. Tendons were found associated with the dorsal and caudal vertebrae in Sauropelta and Minmi, with the caudal vertebrae in Polacanthus, and with the dorsal and distal caudal vertebrae in Ankylosaurus (BROWN 1908, OSTROM 1970, BLOWS 1987, MOLNAR & FREY 1987. OSTROM (1970) suspected that the tendons extended from the anterior or middorsals to as least the midtail. ...
... Each individual row contains scutes of roughly the same size. The large, solid spines in the anterior dorsal region of Gastonia and Polacanthus are absent in Gargoyleosaurus (BLOWS 1987, GASTON et al. 2001. ...
... Among eurypodans, ossified tendons are preserved attached to the sides of the neural spines of the dorsal series of some ankylosaurs and have also been recorded as present along the caudal series, particularly in the clubtailed ankylosaurids (Vickaryous et al., 2004: 383). Some nodosaurids have also been described as having caudal ossified tendons (Blows, 1987;Pereda-Suberbiola, 1993). Ossified tendons are rarely reported in stegosaurs but have been reported in the basal stegosaur Huayangosaurus (Maidment et al., 2006) and in the more derived stegosaurid Hesperosaurus . ...
... Nodosaurid ankylosaurs develop similar shallow and long haemal arches, but the ends of adjacent haemal arches do not interdigitate as they do in ankylosaurids (Coombs, 1978a: fig. 8) and there is no terminal tail club, although large osteoderms have been reported towards the distal end of the tail in some taxa (Blows, 1987). ...
Article
Scelidosaurus fossils were first discovered during the commercial quarrying of the Liassic sea-cliffs between Charmouth and Lyme Regis in Dorset during the late 1850s. The original specimens included a well-preserved skull embedded in a block of argillaceous limestone (marlstone). Shortly after this skull was retrieved, a series of more-or-less contiguous marlstone slabs were recovered, containing most of the skeleton of the same animal (NHMUK R1111). After rudimentary (hammer and chisel) mechanical preparation, Owen published descriptions of this material (Owen, 1861, 1863). These two monographs have been the sole references pertaining to the anatomy of Scelidosaurus for >150 years. The skeleton of the lectotype of Scelidosaurus harrisonii (NHMUK R1111) has since been extracted from the surrounding matrix using an acid-immersion technique. Some additional specimens held in the collections of the Natural History Museum London, the Bristol City Museum and the Sedgwick Museum in Cambridge provide anatomical material that allows detailed description of this taxon, for which we have had, until now, a surprisingly poor understanding. Axial skeleton: The axial skeleton of Scelidosaurus comprises eight cervical, 16 dorsal, four sacral and > 40 caudal vertebrae. During ontogeny, the posterior centrum articular surface of the 16th dorsal vertebra develops a firm, ligament-bonded junction with the succeeding sacral centrum. Apart from the atlas rib, which is single headed, double-headed ribs are present throughout the presacral vertebral series, and none shows any indication of fusion to its associated vertebra. However, those ribs attached to cervical vertebrae 2–4 were evidently bound firmly by connective tissue to rugose diapophyses. The last two (presacral) dorsal ribs show merger of the capitulum and tuberculum, meaning that they are separated by only a step. The angulation and arching of the dorsal ribs suggest that these animals had a broad (barrel-like) torso. Intercostal uncinate plates were present, attached to the posterior margins of some of the largest dorsal ribs. Their attachment sites are clearly marked, and these plates might have been composed of calcified cartilage in larger individuals. The sacral vertebrae fuse progressively during ontogeny, in an anterior-to-posterior sequence. The sacral ribs are long and robust, and tilt the iliac blade outward dorsally. A sacricostal ‘yoke’ (created by the fusion of the distal ends of adjacent sacral ribs) never forms. The base of the tail has a unique ball-and-socket-style joint between the centra of caudal vertebrae 1 and 2 in only one skeleton. This might have permitted powerful, but controlled, movements of the tail as a defensive weapon (or increased flexibility at the base of the tail, which might have been necessary for reproduction). Caudal ribs are initially long, blade-shaped projections that gradually decrease in size and become stub-like remnants that persist as far back as the midtail (approximately caudal vertebra 25). Haemal arches (chevrons) disappear nearer to the distal end of the tail (approximately caudal vertebra 35). Ossified tendons are preserved as epaxial bundles that are clustered in the ‘axillary’ trough (between the neural spine and transverse processes on either side of the midline). Ossified tendons are restricted to the dorsal and sacral region. Flattened ossified tendons are fused to the sides of sacral neural spines. In life, the ossified tendons might have formed a low-angled trellis-like arrangement. Appendicular skeleton: The pectoral girdle comprises a long scapula, with a distally expanded blade. The proximal portion is expanded and supports an oblique promontory, forming an acromial process anteriorly and a thick, collar-like structure posteriorly above the glenoid. Between these two features is a shallow basin, bordered ventrally by a sutural edge for the coracoid. The scapula–coracoid suture remains unfused in large (5-m-long) individuals. The coracoid bears a discrete foramen and forms a subcircular dished plate, with the shallowest of embayments along its posterior edge. Clavicles are present as small fusiform bones attached to the acromial process of the scapulae and leading edge of each coracoid. A sternum was reported as ‘some partially ossified element of the endoskeleton’ Owen (1863: 13), but subsequent preparation of the skeleton has removed all trace of this material. The humerus is relatively long and has a prominent rectangular and proximally positioned deltopectoral crest. The ulna is robust and tapers distally, but there is no evidence of an olecranon process. The radius is more rod-like and terminates distally in an enlarged, subcircular and convex articular surface for the carpus. The carpus is represented by an array of five discoid carpals. The manus is pentadactyl and asymmetrical, with short, divergent metacarpals and digits that terminate in small, arched and pointed unguals on digits 1–3 (only). The phalangeal formula of the manus is 2-3-4-3-2. The pelvis is dominated by a long ilium; the preacetabular process is arched, transversely broad, and curves laterally. In juveniles, this process is short and horizontal, but during ontogeny it increases considerably in length and becomes arched. The iliac blade is tilted laterally, meaning that its dorsal blade partly overhangs the femur. The acetabulum forms a partial cupola, and there is a curtain-like medial wall that reduces the acetabular fenestra to a comparatively low, triangular opening between the pubis and ischium. The postacetabular portion of the ilium is long and supports a brevis shelf. The ischium has a long, laterally compressed shaft that hangs almost vertically beneath the ilium, and there is no obturator process. The pubis has a long, narrow shaft and a relatively short, deep, laterally compressed prepubic process that twists laterally (its distal end lies almost perpendicular to the long axis of the ilium). The articular pad on the pubis for the femoral head faces posteriorly. The obturator foramen is not fully enclosed within the pubis, but its foramen is closed off posteriorly by the pubic peduncle of the ischium. The femur is stout and has a slightly medially offset femoral head, and the greater trochanter forms a sloping shoulder continuous with, and lateral to, the femoral head. The anterior (lesser) trochanter is prominent and forms a thick, thumb-shaped projection on the anterolateral corner of the femoral shaft. The fourth trochanter is pendent and positioned at midshaft. In larger individuals, it appears to become thickened and reinforced by becoming coated with metaplastic bone derived from the tendons attached to its surface. The distal end of the femoral shaft is slightly curved and expands to form condyles. There is a deep and broad posterior intercondylar groove, but the anterior intercondylar groove is barely discernible in juveniles and not much better developed in subadults. The tibia and fibula are shorter than the femur. The tibia is structurally dominant, and the shorter fibula is comparatively slender and bowed. The proximal tarsals are firmly bound by connective tissue to the distal ends of the tibia and fibula. The distal end of the tibia is stepped, which aids the firm interlock between the crus and proximal tarsals. There appear to be two roughly discoid tarsals (distal tarsals 3 and 4), and a rudiment of distal tarsal 5 appears to be sutured to the lateral margin of distal tarsal 4. Five metatarsals are preserved, but the fifth is a splint of bone attached to the proximal end of metatarsal 4. Metatarsals 2–4 are dominant, long and are syndesmotically interlocked proximally, but their shafts splay apart distally. Metatarsal 1 is much shorter than the other three, but it retains two functional phalanges (including a short, pointed ungual). The foot is anatomically tetradactyl but functionally tridactyl. The pedal digit formula is 2-3-4-5-0. The digits diverge, but each appears to curve medially along its length, creating the impression of asymmetry. This asymmetry is emphasized, because the three principal unguals are also twisted medially. The ungual of digit 2 is the largest and most robust of the three, whereas that of digit 4 is the smallest and least robust. The general girth of the torso and the displacement of the abdomen posteriorly (a consequence of the opisthopubic pelvic construction in this dinosaur) constrained the excursion of the hindlimb during the protraction phase of the locomotor cycle. The anterolateral displacement of the hindlimb during protraction is in accord with the freedom of motion that is evident at the acetabulum, the susceptibility of the hindlimb to torsion between and within its component parts, and the asymmetry of the foot. It is probable that thyreophorans (notably, ankylosaurs) used a similar oblique-parasagittal hindlimb excursion to accommodate their equally large and wide abdomens. This surmise accords with the structure of the pelves and hindlimbs of ankylosaurs. Derived stegosaurs might have obviated this ‘problem’, in part, because their hindlimbs were longer and their torsos and abdomens narrower and capable of being ‘stretched’ vertically to a greater extent. Nevertheless, the structure of their acetabula and hindlimbs indicates that the oblique-parasagittal style of hindlimb excursion remained a possibility and might be an evolutionary remnant of the locomotor style of basal, shorter-limbed stegosaurs. A reconstruction of the endoskeleton of Scelidosaurus is presented on the basis of this updated description. Although quadrupedal, this animal was only facultatively so, judged by its forelimb-to-hindlimb proportions and structure; it therefore betrays bipedality in its ancestry.
... The exterior surface of the osteoderm is marked with numerous grooves that give it a spongy texture. Such a morphology and structure have been reported in nodosaurid ankylosaurs (Blows 2001), and is very similar to the large ossicles observed on the sacral shield of Polacanthus from the Barremian of the Isle of Wight (Hulke 1887;Blows 1987, Pereda-Suberbiola 1994. ...
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This contribution describes the continental micro- and macrovertebrate fauna of Angeac- Charente (Berriasian, Early Cretaceous). The rich and diversified fauna includes at least 38 different vertebrate taxa from all major clades, and is represented by more than 50 000 specimens. The Angeac–Charente locality includes the most diverse earliest Cretaceous mixed continental bonebed and Lagerstätte known to date in the World, and it provides a good picture of a Purbeckian paleocommunity. It includes remarkable taxa such as a new ornithomimosaur, a large turiasaur, an helochelydrid turtle and numerous mammals. The vertebrate fauna of Angeac has beyond all a Purberckian character. Many exclusively European genera and species belong to families with an essentially Laurasian paleogeographic distribution. Some taxa nevertheless suggest dispersal events between Africa and Europe at the Jurassic/Cretaceous transition. The successive Charente faunas of Chassiron (Tithonian), Cherves–de–Cognac (Berriasian) and Angeac–Charente improve our poor knowledge of the evolution of continental vertebrate faunas at the Jurassic/Cretaceous transition. Rather than reflecting an important faunal turnover between the Tithonian and the Berriasian, they record environmental changes related to the sea–level regression that characterizes the end of the Jurassic.
... Though their fossils are known from sediments ranging from the Middle Jurassic to the uppermost Cretaceous, specimens are in many cases fragmentary with poorly preserved cranial material (see Ősi 2015 for a review). Multiple articulated or associated specimens of a single genus from Europe are only known in a few taxa: the Valanginian Hylaeosaurus based on two partial skeletons (Mantell 1833(Mantell , 1841Owen 1858;Pereda-Suberbiola 1993a;Carpenter 2001), the Barremian-early Aptian Polacanthus based on three partial skeletons (Owen 1865;Hulke 1882Hulke , 1888Blows 1982Blows , 1987Blows , 1996Blows , 2015Pereda-Suberbiola 1994;Naish and Martill 2001), the Albian Europelta based on five skeletons (Kirkland et al. 2013;Luis Alcalá, pers. comm, 2014) and the Santonian Hungarosaurus based on six associated skeletons (Ősi 2005;Ősi and Makádi 2009;Ősi 2015, in the paper). ...
Article
Ankylosaurian fossils are usually standard elements of Cretaceous continental vertebrate localities; however, bone-yielding horizons including more than one individual are extremely rare. Here, we present a unique assemblage of 12 partial, articulated or associated ankylosaurian skeletons and thousands of isolated bones and teeth discovered from the Santonian Iharkút vertebrate locality, western Hungary. Collected from an area of 600 m2 and from a single bone bed, this material is one of the richest ankylosaurian accumulation worldwide. The 12 skeletons are not monospecific but mostly based on the pelvic armour composition: six of them are from Hungarosaurus, two are referred to Struthiosaurus and four can be assigned to Nodosauridae indet. Sedimentological and taphonomical examinations revealed a single mass mortality event as the cause of the death and accumulation of these quadruped animals that are described here. The ankylosaur assemblage from Iharkút suggests at least a temporarily gregarious behaviour of these animals and also shows that Hungarosaurus and Struthiosaurus might live in the same moist habitat or at least preferred relatively close environments.
... The osteoderms of the pelvic region are coossified into a continuous pelvic shield in the basal ankylosaurs Gastonia and Mymoorapelta, and in many nodosaurids (e.g., Taohelong, Nodosaurus, and Polacanthus), and are tightly appressed in the basal ankylosaurid Aletopelta (Lull 1921;Blows 1987;Kirkland and Carpenter 1994;Kirkland 1998;Yang et al. 2013;Arbour and Currie 2016). Pelvic osteoderms in ankylosaurines are preserved in several North American (Scolosaurus) and Asian (cf. ...
Article
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Ankylosaurus magniventris is an iconic dinosaur species often depicted in popular media. It is known from relatively fragmentary remains compared with its earlier and smaller relatives such as Euoplocephalus and Anodontosaurus. Nevertheless, the known fossils of Ankylosaurus indicate that it had diverged significantly in cranial and postcranial anatomy compared with other Laramidian ankylosaurines. In particular, the dentition, narial region, tail club, and overall body size differ substantially from other Campanian–Maastrichtian ankylosaurines. We review the anatomy of this unusual ankylosaur using data from historic and newly identified material and discuss its palaeoecological implications.
... between North America and Europe prior to complete separation is well documented (e.g., Galton, 1980). Continued intercontinental connection during the Early Cretaceous is best seen by the polacanthid Gastonia in the Yellow Cat and basal part of the Ruby Ranch Members and the very similar Po/acanthus from the upper part of the Wessex and base of the Vectis Formations on the Isle of Wight (Blows, 1987;Pereda-Suberbiola, 1994). This interval of occurrence of Po/acanthus straddles the Hauterivian-Barremian boundary (Benton and Spencer, 1995;Feist et al., 1995) and supports other evidence discussed above for the Yellow Cat being at least Barremian in age. ...
Conference Paper
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The Cedar Mountain and Dakota Formations of eastern Utah preserve two distinct biostratigraphical dinosaur faunas that record the severing of a North American-European connection, and the opening of an North American-Asian connection as the North American Plate drifted westward. The older Yell ow Cat Fauna, of the Yellow Cat through to the lower Ruby Ranch Members of the Cedar Mountain Formation, is dominated by polacanthid ankylosaurs, brachiosaurid and titanosaurid sauropods, and iguanodontids much like those of the Wealden of southern England. The polacanthid ankylosaur, the brachiosaurid sauropods and a coelurosaurid theropod indicates that the Yellow Cat Fauna is a relict of the older Late Jurassic Morrison Fauna. The younger Mussentuchit Fauna from the top of the Ruby Ranch and Mussentuchit Members and from the Dakota Formation, shows an Asian influence as characterized by a shamosaur-like ankylosaurid similar to those of Asia, the first appearance of a neoceratopsian, and the presence of the triconodont mammal, Gobiconodon. Various age dates on the faunas indicate that separation between the North America and western part of the Eurasian Plates was completed by the end of the Barremian and that a connection between North American and eastern Eurasian Plates was established no later than the early Albian.
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Postcranial elements (cervical, sacral and caudal vertebrae, as well as ilium, rib and limb bone fragments) belonging to a gigantic tetanuran theropod were recovered from the basal unit (the White Rock Sandstone equivalent) of the Vectis Formation near Compton Chine, on the southwest coast of the Isle of Wight. These remains appear to pertain to the same individual, with enormous dimensions similar to those of the Spinosaurus holotype and exceeding those of the largest European theropods previously reported. A combination of features—including the presence of spinodiapophyseal webbing on an anterior caudal vertebra—suggest that this is a member of Spinosauridae, though a lack of convincing autapomorphies precludes the identification of a new taxon. Phylogenetic analysis supports spinosaurid affinities but we were unable to determine a more precise position within the clade weak support for a position within Spinosaurinae or an early-diverging position within Spinosauridae were found in some data runs. Bioerosion in the form of curved tubes is evident on several pieces, potentially related to harvesting behaviour by coleopteran bioeroders. This is the first spinosaurid reported from the Vectis Formation and the youngest British material referred to the clade. This Vectis Formation spinosaurid is unusual in that the majority of dinosaurs from the Lower Cretaceous units of the Wealden Supergroup are from the fluviolacustrine deposits of the underlying Barremian Wessex Formation. In contrast, the lagoonal facies of the upper Barremian–lower Aptian Vectis Formation only rarely yield dinosaur material. Our conclusions are in keeping with previous studies that emphasise western Europe as a pivotal region within spinosaurid origination and diversification.
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Fragmentary but associated dinosaur bones collected in 1930 from the Pine River of northeastern British Columbia are identified here as originating from an ankylosaur. The specimen represents only the second occurrence of dinosaur skeletal material from the Cenomanian Dunvegan Formation and the first from Dunvegan outcrops in the province of British Columbia. Nodosaurid ankylosaur footprints are common ichnofossils in the formation, but the skeletal material described here is too fragmentary to confidently assign to either a nodosaurid or ankylosaurid ankylosaur. The Cenomanian is a time of major terrestrial faunal transitions in North America, but many localities of this age are located in the southern United States; the discovery of skeletal fossils from the Pine River demonstrates the potential for the Dunvegan Formation to produce terrestrial vertebrate fossils that may provide important new data on this significant transitional period during the Cretaceous.
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Ankylosaurs are relatively common in the Cedar Mountain Formation and include (1) Gastonia burgei, (2) Sauropelta sp., and (3) Animantarx ramaljonesi new genus, new species. Animantarx ramaljonesi is characterized by a highly domed cranium, very small postorbital "horns," moderately developed lateral notch in the skull roof for the lateral temporal fenestra, indistinguishable pattern of armor on the skull roof, small quadratojugal "hom," elongated coracoid that is about 63% of the scapula length, a high shoulder on the deltopectoral crest, and an oblique ridge on anterolateral surface of the femur below the lesser trochanter. The Cedar Mountain ankylosaurs appear to be restricted to distinct stratigraphic units: Gastonia burgei to the Yellow Cat Member, Sauropelta sp. to the Poison Strip Sandstone, and Animantarx ramaljonesi to the Mussentuchit Member. Provisionally, such a distribution supports a threefold division of the Cedar Mountain dinosaur faunas. The diversity of ankylosaurs in the Cedar Mountain is the highest of any Lower Cretaceous formation and may eventually provide important information about the evolution and adaptive radiation of these dinosaurs.
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