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= = = Health hazard = = =
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Since Islais Creek is a culvert that carries storm water , domestic sewage , and industrial wastewater , it is possible for the sewage to overflow . Such overflow can cause a public health hazard as Islais Creek displays higher level of heavy metals , PCBs , bacteria , as well as organochlorines than other parts of th... |
= = Transportation = =
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The Third Street Bridge is the major crossing of the creek , carrying T Third Street light rail line and Third Street . It is a bascule @-@ type drawbridge . The Port of San Francisco extended Illinois Street across Islais Creek in 2006 to relieve traffic for Third Street . This crossing also uses a bascule bridge .
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= Iguanodon =
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Iguanodon ( / ᵻˈɡwɑːnədɒn / i @-@ GWAH @-@ nə @-@ don ; meaning " iguana @-@ tooth " ) is a genus of ornithopod dinosaur that existed roughly halfway between the first of the swift bipedal hypsilophodontids of the mid @-@ Jurassic and the duck @-@ billed dinosaurs of the late Cretaceous . While many species have been ... |
The genus was named in 1825 by English geologist Gideon Mantell , based on fossil specimens that are now assigned to Therosaurus and Mantellodon . Iguanodon was the second type of dinosaur formally named based on fossil specimens , after Megalosaurus . Together with Megalosaurus and Hylaeosaurus , it was one of the th... |
Scientific understanding of Iguanodon has evolved over time as new information has been obtained from fossils . The numerous specimens of this genus , including nearly complete skeletons from two well @-@ known bonebeds , have allowed researchers to make informed hypotheses regarding many aspects of the living animal ... |
= = Description = =
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Iguanodon were bulky herbivores that could shift from bipedality to quadrupedality . The only well @-@ supported species , I. bernissartensis , is estimated to have weighed about 3 @.@ 08 tonnes ( 3 @.@ 4 tons ) on average , and measured about 10 metres ( 33 feet ) long as an adult , with some specimens possibly as lo... |
The arms of I. bernissartensis were long ( up to 75 % the length of the legs ) and robust , with rather inflexible hands built so that the three central fingers could bear weight . The thumbs were conical spikes that stuck out away from the three main digits . In early restorations , the spike was placed on the animal... |
Iguanodon teeth are , as the name suggests , like those of an iguana , but larger . Unlike hadrosaurids , which had columns of replacement teeth , Iguanodon only had one replacement tooth at a time for each position . The upper jaw held up to 29 teeth per side , with none at the front of the jaw , and the lower jaw 25... |
= = Classification and origins = =
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Iguanodon gives its name to the unranked clade Iguanodontia , a very populous group of ornithopods with many species known from the Middle Jurassic to the Late Cretaceous . Aside from Iguanodon , the best @-@ known members of the clade include Dryosaurus , Camptosaurus , Ouranosaurus , and the duck @-@ bills , or hadr... |
With the advent of cladistic analyses , Iguanodontidae as traditionally construed was shown to be paraphyletic , and these animals are recognised to fall at different points in relation to hadrosaurs on a cladogram , instead of in a single distinct clade . Essentially , the modern concept of Iguanodontidae currently i... |
The cladogram below follows an analysis by Andrew McDonald , 2012 .
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= = Palaeobiology = =
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= = = Feeding = = =
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One of the first details noted about Iguanodon was that it had the teeth of a herbivorous reptile , although there has not always been consensus on how it ate . As Mantell noted , the remains he was working with were unlike any modern reptile , especially in the toothless , scoop @-@ shaped form of the lower jaw symph... |
The skull was structured in such a way that as it closed , the bones holding the teeth in the upper jaw would bow out . This would cause the lower surfaces of the upper jaw teeth to rub against the upper surface of the lower jaw 's teeth , grinding anything caught in between and providing an action that is the rough e... |
Exactly what Iguanodon ate with its well @-@ developed jaws is not known . The size of the larger species , such as I. bernissartensis , would have allowed them access to food from ground level to tree foliage at 4 – 5 metres ( 13 – 16 ft ) high . A diet of horsetails , cycads , and conifers was suggested by David Nor... |
= = = Posture and movement = = =
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Early fossil remains were fragmentary , which led to much speculation on the posture and nature of Iguanodon . Iguanodon was initially portrayed as a quadrupedal horn @-@ nosed beast . However , as more bones were discovered , Mantell observed that the forelimbs were much smaller than the hindlimbs . His rival Owen wa... |
During his re @-@ examination of Iguanodon , David Norman was able to show that this posture was unlikely , because the long tail was stiffened with ossified tendons . To get the tripodal pose , the tail would literally have to be broken . Putting the animal in a horizontal posture makes many aspects of the arms and p... |
Furthermore , it appears that Iguanodon became more quadrupedal as it got older and heavier ; juvenile I. bernissartensis have shorter arms than adults ( 60 % of hindlimb length versus 70 % for adults ) . When walking as a quadruped , the animal 's hands would have been held so that the palms faced each other , as sho... |
Large three @-@ toed footprints are known in Early Cretaceous rocks of England , particularly Wealden beds on the Isle of Wight , and these trace fossils were originally difficult to interpret . Some authors associated them with dinosaurs early on . In 1846 , E. Tagert went so far as to assign them to an ichnogenus he... |
= = = Thumb spike = = =
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The thumb spike is one of the best @-@ known features of Iguanodon . Although it was originally placed on the animal 's nose by Mantell , the complete Bernissart specimens allowed Dollo to place it correctly on the hand , as a modified thumb . ( This would not be the last time a dinosaur 's modified thumb claw would b... |
This thumb is typically interpreted as a close @-@ quarter stiletto @-@ like weapon against predators , although it could also have been used to break into seeds and fruits , or against other Iguanodon . One author has suggested that the spike was attached to a venom gland , but this has not been accepted , as the spi... |
= = = Possible social behaviour = = =
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Although sometimes interpreted as the result of a single catastrophe , the Bernissart finds instead are now interpreted as recording multiple events . According to this interpretation , at least three occasions of mortality are recorded , and though numerous individuals would have died in a geologically short time spa... |
An argument against herding is that juvenile remains are very uncommon at this site , unlike modern cases with herd mortality . They more likely were the periodic victims of flash floods whose carcasses accumulated in a lake or marshy setting . The Nehden find , however , with its greater span of individual ages , mor... |
Unlike other purported herding dinosaurs ( especially hadrosaurs and ceratopsids ) , there is no evidence that Iguanodon was sexually dimorphic , with one sex appreciably different from the other . At one time , it was suggested that the Bernissart I. " mantelli " , or I. atherfieldensis ( Dollodon and Mantellisaurus ... |
= = = Paleopathology = = =
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Evidence of a fractured hip bone was found in a specimen of Iguanodon , which had an injury to its ischium . Two other individuals were observed with signs of osteoarthritis as evidenced by bone overgrowths in their anklebones which are called osteophytes .
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= = Discovery and history = =
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= = = Gideon Mantell , Sir Richard Owen , and the discovery of dinosaurs = = =
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The discovery of Iguanodon has long been accompanied by a popular legend . The story goes that Gideon Mantell 's wife , Mary Ann , discovered the first teeth of an Iguanodon in the strata of Tilgate Forest in Whitemans Green , Cuckfield , Sussex , England , in 1822 while her husband was visiting a patient . However , ... |
In recognition of the resemblance of the teeth to those of the iguana , Mantell decided to name his new animal Iguanodon or " iguana @-@ tooth " , from iguana and the Greek word ὀδών ( odon , odontos or " tooth " ) . Based on isometric scaling , he estimated that the creature might have been up to 18 metres ( 59 feet ... |
Mantell sent a letter detailing his discovery to the local Portsmouth Philosophical Society in December 1824 , several weeks after settling on a name for the fossil creature . The letter was read to members of the Society at a meeting on 17 December , and a report was published in the Hampshire Telegraph the following... |
A more complete specimen of similar animal was discovered in a quarry in Maidstone , Kent , in 1834 ( lower Lower Greensand Formation ) , which Mantell soon acquired . He was led to identify it as an Iguanodon based on its distinctive teeth . The Maidstone slab was utilized in the first skeletal reconstructions and ar... |
At the same time , tension began to build between Mantell and Richard Owen , an ambitious scientist with much better funding and society connections in the turbulent worlds of Reform Act – era British politics and science . Owen , a firm creationist , opposed the early versions of evolutionary science ( " transmutatio... |
In 1849 , a few years before his death in 1852 , Mantell realised that iguanodonts were not heavy , pachyderm @-@ like animals , as Owen was putting forward , but had slender forelimbs ; however , his passing left him unable to participate in the creation of the Crystal Palace dinosaur sculptures , and so Owen 's visi... |
= = = Bernissart = = =
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The largest find of Iguanodon remains to that date occurred on 28 February 1878 in a coal mine at Bernissart in Belgium , at a depth of 322 m ( 1 @,@ 056 ft ) , when two mineworkers , Jules Créteur and Alphonse Blanchard , accidentally hit on a skeleton that they initially took for petrified wood . With the encouragem... |
The science of conserving fossil remains was in its infancy , and new techniques had to be improvised to deal with what soon became known as " pyrite disease " . Crystalline pyrite in the bones was being oxidized to iron sulphate , accompanied by an increase in volume that caused the remains to crack and crumble . Whe... |
Dollo 's specimens allowed him to show that Owen 's prehistoric pachyderms were not correct for Iguanodon . He instead modelled the skeletal mounts after the cassowary and wallaby , and put the spike that had been on the nose firmly on the thumb . He was not completely correct , but he also had the disadvantage of bei... |
Excavations at the quarry were stopped in 1881 , although it was not exhausted of fossils , as recent drilling operations have shown . During World War I , when the town was occupied by German forces , preparations were made to reopen the mine for palaeontology , and Otto Jaekel was sent from Berlin to supervise . The... |
= = = Current research = = =
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Research on Iguanodon decreased during the early part of the 20th century as World Wars and the Great Depression enveloped Europe . A new species that would become the subject of much study and taxonomic controversy , I. atherfieldensis , was named in 1925 by R. W. Hooley , for a specimen collected at Atherfield Point... |
Iguanodon was recorded from Africa based on teeth from Tunisia and elsewhere in the Sahara , but the description of Lurdusaurus and Ouranosaurus cast doubt on African records of Iguanodon . The genus was also recorded from Mongolia based on the description of I. orientalis , and in North America based on I. ottingeri ... |
Iguanodon was not part of the initial work of the dinosaur renaissance that began with the description of Deinonychus in 1969 , but it was not neglected for long . David B. Weishampel 's work on ornithopod feeding mechanisms provided a better understanding of how it fed , and David B. Norman 's work on numerous aspect... |
Iguanodon material has also been used in the search for dinosaur DNA and other biomolecules . In research by Graham Embery et al . , Iguanodon bones were processed to look for remnant proteins . In this research , identifiable remains of typical bone proteins , such as phosphoproteins and proteoglycans , were found in... |
= = Species = =
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Because Iguanodon is one of the first dinosaur genera to have been named , numerous species have been assigned to it . While never becoming the wastebasket taxon several other early genera of dinosaurs became ( such as Megalosaurus ) , Iguanodon has had a complicated history , and its taxonomy continues to undergo rev... |
I. anglicus was the original type species , but the holotype was based on a single tooth and only partial remains of the species have been recovered since . In March 2000 , the International Commission on Zoological Nomenclature changed the type species to the much better known I. bernissartensis , with the new holoty... |
= = = Species currently accepted as valid = = =
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Only two species assigned to Iguanodon are still considered to be valid .
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I. bernissartensis , described by George Albert Boulenger in 1881 , is the type species for the genus . This species is best known for the many skeletons discovered in Bernissart , but is also known from remains across Europe . David Norman suggested that it includes the dubious Mongolian I. orientalis , but this has ... |
I. galvensis , described in 2015 , is based on adult and juvenile remains found in Barremian @-@ age deposits in Teruel , Spain .
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= = = Reassigned species = = =
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I. hoggi ( also spelled I. boggii or hoggii ) , named by Owen for a lower jaw from the Tithonian – Berriasian @-@ age Upper Jurassic – Lower Cretaceous Purbeck Beds of Dorset in 1874 , has been reassigned to its own genus , Owenodon .
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Iguanodon albinus ( or Albisaurus scutifer ) , described by Czech palaeontologist Antonin Fritsch in 1893 , is a dubious nondinosaurian reptile now known as Albisaurus albinus .
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I. atherfieldensis , described by R.W. Hooley in 1925 , was smaller and less robust than I. bernissartensis , with longer neural spines . It was renamed Mantellisaurus atherfieldensis in 2007 . The Bernissart specimen RBINS 1551 was described as Dollodon bampingi in 2008 , but McDonald and Norman returned Dollodon to ... |
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