Iguanodon

Iguanodon

Overview
Iguanodon is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of ornithopod
Ornithopod
Ornithopods or members of the clade Ornithopoda are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American...

 dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

 that lived roughly halfway between the first of the swift bipedal hypsilophodont
Hypsilophodont
Hypsilophodonts were small ornithopod dinosaurs, regarded as fast, herbivorous bipeds on the order of 1–2 meters long . They are known from Asia, Australia, Europe, New Zealand, North America, and South America, from rocks of Middle Jurassic to late Cretaceous age...

ids and the ornithopods' culmination in the duck-billed
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

 dinosaurs. Many species of Iguanodon have been named, dating from the Kimmeridgian
Kimmeridgian
In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma . The Kimmeridgian follows the Oxfordian and precedes the Tithonian....

 age of the Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...

 Period to the Cenomanian
Cenomanian
The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...

 age of the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

 Period from Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. However, research in the first decade of the 21st century suggests that there is only one well-substantiated species: I.
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Unanswered Questions
Encyclopedia
Iguanodon is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of ornithopod
Ornithopod
Ornithopods or members of the clade Ornithopoda are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American...

 dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

 that lived roughly halfway between the first of the swift bipedal hypsilophodont
Hypsilophodont
Hypsilophodonts were small ornithopod dinosaurs, regarded as fast, herbivorous bipeds on the order of 1–2 meters long . They are known from Asia, Australia, Europe, New Zealand, North America, and South America, from rocks of Middle Jurassic to late Cretaceous age...

ids and the ornithopods' culmination in the duck-billed
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

 dinosaurs. Many species of Iguanodon have been named, dating from the Kimmeridgian
Kimmeridgian
In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma . The Kimmeridgian follows the Oxfordian and precedes the Tithonian....

 age of the Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...

 Period to the Cenomanian
Cenomanian
The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...

 age of the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

 Period from Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. However, research in the first decade of the 21st century suggests that there is only one well-substantiated species: I. bernissartensis, that lived from the late Barremian
Barremian
The Barremian is an age in the geologic timescale between 130.0 ± 1.5 Ma and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch...

 to the earliest Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...

 ages (Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

) in Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

, between about 126 and 125 million years ago. Iguanodons most distinctive features were its large thumb spikes, which were possibly used for defence against predator
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...

s, combined with long prehensile fifth fingers able to forage for food.

Named in 1825 by English
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 geologist
Geologist
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes and history that has shaped it. Geologists usually engage in studying geology. Geologists, studying more of an applied science than a theoretical one, must approach Geology using...

 Gideon Mantell
Gideon Mantell
Gideon Algernon Mantell MRCS FRS was an English obstetrician, geologist and palaeontologist...

, Iguanodon was the second dinosaur formally named, after Megalosaurus
Megalosaurus
Megalosaurus is a genus of large meat-eating theropod dinosaurs of the Middle Jurassic period of Europe...

. Together with Megalosaurus and Hylaeosaurus
Hylaeosaurus
Hylaeosaurus is the most obscure of the three animals used by Sir Richard Owen to first define the new group Dinosauria, in 1842. The original specimen, recovered by Gideon Mantell from the Tilgate Forest in the south of England in 1832, now resides in the Natural History Museum of London, where...

, it was one of the three genera originally used to define Dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

ia. A large, bulky herbivore, Iguanodon is a member of Iguanodont
Iguanodont
Iguanodonts were herbivorous dinosaurs that lived from the mid-Jurassic to Late Cretaceous. Some members include Camptosaurus, Callovosaurus, Iguanodon, Ouranosaurus, and the hadrosaurids or "duck-billed dinosaurs". Iguanodonts were one of the first groups of dinosaurs to be found...

ia, along with the duck-billed hadrosaur
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

s. The taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 of this genus continues to be a topic of study as new species are named or long-standing ones reassigned to other genera.

Scientific understanding of Iguanodon has evolved over time as new information has been obtained from the fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s. The numerous specimens of this genus, including nearly complete skeletons from two well-known bonebed
Bone bed
A bone bed is any geological stratum or deposit that contains bones of whatever kind. Inevitably, such deposits are sedimentary in nature. Not a formal term, it tends to be used more to describe especially dense collections...

s, have allowed researchers to make informed hypotheses
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...

 regarding many aspects of the living animal, including feeding, movement, and social behaviour. As one of the first scientifically well-known dinosaurs, Iguanodon has occupied a small but notable place in the public's perception of dinosaurs, its artistic representation changing significantly in response to new interpretations of its remains.

Description


Iguanodon was a bulky herbivore that could shift from bipedality to quadruped
Quadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...

ality. The best-known species, I. bernissartensis, is estimated to have weighed about 3 tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...

s (3.5 ton
Short ton
The short ton is a unit of mass equal to . In the United States it is often called simply ton without distinguishing it from the metric ton or the long ton ; rather, the other two are specifically noted. There are, however, some U.S...

s) on average, and measured about 10 metres long (33 ft) as an adult, with some specimens possibly as long as 13 metres (43 ft). This genus had a large, tall but narrow skull, with a toothless beak
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...

 probably covered with keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...

, and teeth like those of an iguana
Iguana
Iguana is a herbivorous genus of lizard native to tropical areas of Central America and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena...

, but much larger and more closely packed.

The arms were long (up to 75% the length of the legs in I. bernissartensis) 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's nose. Later fossils revealed the true nature of the thumb spikes, although their exact function is still debated. They could have been used for defense, or for foraging for food. The little finger
Little finger
The little finger, often called the pinky in American English, pinkie in Scottish English , or small finger in medicine, is the most ulnar and usually smallest finger of the human hand, opposite the thumb, next to the ring finger.-Muscles:There are four muscles that...

 was elongated and dextrous, and could have been used to manipulate objects. The legs were powerful, but not built for running, and each foot had three toes. The backbone and tail were supported and stiffened by ossified
Ossification
Ossification is the process of laying down new bone material by cells called osteoblasts. It is synonymous with bone tissue formation...

 tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...

s, which were tendons that turned to bone during life (these rod-like bones are usually omitted from skeletal mounts and drawings). Overall, in body structure, it was not too dissimilar from its later relatives, the hadrosaurid
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

s.

Classification and origins




Iguanodon gives its name to the unranked
Linnaean taxonomy
Linnaean taxonomy can mean either of two related concepts:# the particular form of biological classification set up by Carl Linnaeus, as set forth in his Systema Naturæ and subsequent works...

 clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 Iguanodont
Iguanodont
Iguanodonts were herbivorous dinosaurs that lived from the mid-Jurassic to Late Cretaceous. Some members include Camptosaurus, Callovosaurus, Iguanodon, Ouranosaurus, and the hadrosaurids or "duck-billed dinosaurs". Iguanodonts were one of the first groups of dinosaurs to be found...

ia, a very populous group of ornithopods with many species known from the Middle Jurassic
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....

 to the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

. Aside from Iguanodon, the best-known members of the clade include Dryosaurus
Dryosaurus
Dryosaurus is a genus of an ornithopod dinosaur that lived in the Late Jurassic period. It was an iguanodont . Fossils have been found in the western United States, and were first discovered in the late 19th century...

, Camptosaurus
Camptosaurus
Camptosaurus is a genus of plant-eating, beaked ornithischian dinosaurs of the Late Jurassic period of western North America. The name means 'flexible lizard', ....

, Ouranosaurus
Ouranosaurus
Ouranosaurus is an unusual genus of herbivorous iguanodont dinosaur that lived during the early Cretaceous about 110 million years ago in what is now Africa. Ouranosaurus measured about seven to eight meters long...

, and the duck-bills, or hadrosaur
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

s. In older sources, Iguanodontidae was shown as a distinct family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

. This family traditionally has been something of a wastebasket taxon, including ornithopods that were neither hypsilophodontids or hadrosaurids. In practice, animals like Callovosaurus
Callovosaurus
Callovosaurus is a genus of iguanodontian dinosaur known from most of a left thigh bone discovered in Middle Jurassic-age rocks of England. At times, it has been considered dubious or a valid genus of basal iguanodontian, perhaps a dryosaurid.-History and description:Callovosaurus is based on...

, Camptosaurus, Craspedodon
Craspedodon
Craspedodon is an extinct genus of ornithischian dinosaur, possibly a ceratopsian. It lived during the Late Cretaceous , in what is now Belgium. Only a few teeth have ever been found, which were described as similar to those of Iguanodon...

, Kangnasaurus
Kangnasaurus
Kangnasaurus is a genus of iguanodontian ornithopod dinosaur found in supposedly Early Cretaceous rocks of South Africa. It is known from a tooth and possibly some postcranial remains. At times, it has been considered dubious or a valid genus...

, Mochlodon
Mochlodon
Mochlodon is a genus of iguanodont dinosaur from the Late Cretaceous.In 1859 coal mine administrator Pawlowitsch notified the University of Vienna that some fossils had been found in the Gute Hoffnung mine at Muthmannsdorf in Austria...

, Muttaburrasaurus
Muttaburrasaurus
Muttaburrasaurus is a genus of herbivorous ornithopod dinosaur, living in what is now northeastern Australia between 100 and 98 million years ago during the early Cretaceous Period. It has been recovered in some analyses as a member of the iguanodontian family Rhabdodontidae...

, Ouranosaurus, and Probactrosaurus
Probactrosaurus
Probactrosaurus is an early herbivorous hadrosauroid iguanodont dinosaur. It lived in China during the Early Cretaceous period....

 were usually assigned to this family. With the advent of cladistic analyses
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

, Iguanodontidae as traditionally construed was shown to be paraphyletic
Paraphyly
A group of taxa is said to be paraphyletic if the group consists of all the descendants of a hypothetical closest common ancestor minus one or more monophyletic groups of descendants...

, 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 includes only Iguanodon. Groups like Iguanodontoidea are still used as unranked clades in the scientific literature, though many traditional iguanodontids are now included in the superfamily Hadrosauroidea
Hadrosauroidea
Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or hadrosaurids, and their close relatives. Many primitive hadrosauroids, such as the sail-backed Ouranosaurus, have traditionally been included in a paraphyletic "Iguanodontidae"...

. Iguanodon lies between Camptosaurus and Ouranosaurus in cladograms, and is probably descended from a camptosaur-like animal. At one point, Jack Horner
Jack Horner (paleontologist)
John "Jack" R. Horner is an American paleontologist who discovered and named Maiasaura, providing the first clear evidence that some dinosaurs cared for their young. He is one of the best-known paleontologists in the United States...

 suggested, based mostly on skull features
Synapomorphy
In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...

, that hadrosaurids actually formed two more distantly related groups, with Iguanodon on the line to the flat-headed hadrosaurines
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

, and Ouranosaurus on the line to the crested lambeosaurines
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

, but his proposal has been rejected.

Gideon Mantell, Sir Richard Owen, and the discovery of dinosaurs



The discovery of Iguanodon has long been accompanied by a popular legend
Legend
A legend is a narrative of human actions that are perceived both by teller and listeners to take place within human history and to possess certain qualities that give the tale verisimilitude...

. The story goes that Gideon Mantell
Gideon Mantell
Gideon Algernon Mantell MRCS FRS was an English obstetrician, geologist and palaeontologist...

's wife, Mary Ann, discovered the first teeth of an Iguanodon in the strata of Tilgate Forest in Whitemans Green
Whitemans Green
Whiteman's Green is a place in the north of the large village and civil parish of Cuckfield in the Mid Sussex District of West Sussex, England. It is located on the southern slopes of the Weald, two miles west of Haywards Heath and surrounded on other sides by Cuckfield Rural civil parish. The...

, Cuckfield
Cuckfield
Cuckfield is a large village and civil parish in the Mid Sussex District of West Sussex, England, on the southern slopes of the Weald. It lies south of London, north of Brighton, and east northeast of the county town of Chichester. Nearby towns include Haywards Heath to the southeast and Burgess...

, Sussex
Sussex
Sussex , from the Old English Sūþsēaxe , is an historic county in South East England corresponding roughly in area to the ancient Kingdom of Sussex. It is bounded on the north by Surrey, east by Kent, south by the English Channel, and west by Hampshire, and is divided for local government into West...

, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, in 1822 while her husband was visiting a patient. However, there is no evidence that Mantell took his wife with him while seeing patients. Furthermore, he admitted in 1851 that he himself had found the teeth. Not everyone agrees that the story is false, though. It is known from his notebooks that Mantell first acquired large fossil bones from the quarry at Whitemans Green in 1820. Because also theropod teeth were found, thus belonging to carnivores, he at first interpreted these bones, which he tried to combine into a partial skeleton, as those of a giant crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...

. In 1821 Mantell mentioned the find of herbivorous teeth and began to consider the possibility that a large herbivorous reptile was present in the strata. However, in his 1822 publication Fossils of the South Downs he as yet did not dare to suggest a connection between the teeth and his very incomplete skeleton, presuming that his finds presented two large forms, one carnivorous ("an animal of the Lizard Tribe of enormous magnitude"), the other herbivorous. In May 1822 he first presented the herbivorous teeth to the Geological Society of London
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

 but the members, among which William Buckland
William Buckland
The Very Rev. Dr William Buckland DD FRS was an English geologist, palaeontologist and Dean of Westminster, who wrote the first full account of a fossil dinosaur, which he named Megalosaurus...

, dismissed them as fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 teeth or the incisors of a rhinoceros
Rhinoceros
Rhinoceros , also known as rhino, is a group of five extant species of odd-toed ungulates in the family Rhinocerotidae. Two of these species are native to Africa and three to southern Asia....

 from a Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

 stratum. On 23 June 1823 Charles Lyell
Charles Lyell
Sir Charles Lyell, 1st Baronet, Kt FRS was a British lawyer and the foremost geologist of his day. He is best known as the author of Principles of Geology, which popularised James Hutton's concepts of uniformitarianism – the idea that the earth was shaped by slow-moving forces still in operation...

 showed some to Georges Cuvier
Georges Cuvier
Georges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...

, during a soiree in Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

, but the famous French naturalist at once discarded them as those of a rhinoceros. Though Cuvier the very next day retracted, Lyell only reported the dismissal to Mantell, who became rather diffident about the issue. In 1824 Buckland described Megalosaurus
Megalosaurus
Megalosaurus is a genus of large meat-eating theropod dinosaurs of the Middle Jurassic period of Europe...

 and was on that occasion invited to visit Mantell's collection. Seeing the bones on 6 March he agreed that these were of some giant saurian — though still denying it was a herbivore. Emboldened nevertheless, Mantell again sent some teeth to Cuvier, who answered on 22 June 1824 that he had determined that they were reptilian and quite possibly belonged to a giant herbivore. In a new edition that year of his Recherches sur les Ossemens Fossiles Cuvier admitted his earlier mistake, leading to an immediate acceptance of Mantell, and his new saurian, in scientific circles. Mantell tried to further corroborate his theory by finding a modern-day parallel among extant reptiles. In September 1824 he visited the Royal College of Surgeons
Royal College of Surgeons of England
The Royal College of Surgeons of England is an independent professional body and registered charity committed to promoting and advancing the highest standards of surgical care for patients, regulating surgery, including dentistry, in England and Wales...

 but at first failed to find comparable teeth. However, assistant-curator Samuel Stutchbury
Samuel Stutchbury
-External links:**...

 recognised that they resembled those of an iguana he had recently prepared, albeit twenty times longer. Mantell did not describe his findings until 10 February 1825, when he presented a paper on the remains to the Royal Geological Society of London
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

.

In recognition of the resemblance of the teeth to those of the iguana, Mantell named his new genus Iguanodon or "iguana-tooth", from iguana and the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 word ὀδών (odon, odontos or "tooth"). Based on isometric scaling, he estimated that the creature might have been up to 18 metres (60 ft) long, more than the 12 metres (40 ft) length of Megalosaurus. His initial idea for a name was Iguana-saurus ("Iguana lizard"), but his friend William Daniel Conybeare
William Daniel Conybeare
William Daniel Conybeare FRS , dean of Llandaff, was an English geologist, palaeontologist and clergyman. He is probably best known for his ground-breaking work on marine reptile fossils in the 1820s, including important papers for the Geological Society of London on ichthyosaur anatomy and the...

 suggested that that name was more applicable to the iguana itself, so a better name would be Iguanoides ("Iguana-like") or Iguanodon. He neglected to add a specific name to form a proper binomial
Binomial nomenclature
Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...

, so one was supplied in 1829 by Friedrich Holl: I. anglicum, which was later amended to I. anglicus.

A better specimen was discovered in a quarry in Maidstone
Maidstone
Maidstone is the county town of Kent, England, south-east of London. The River Medway runs through the centre of the town linking Maidstone to Rochester and the Thames Estuary. Historically, the river was a source and route for much of the town's trade. Maidstone was the centre of the agricultural...

, Kent
Kent
Kent is a county in southeast England, and is one of the home counties. It borders East Sussex, Surrey and Greater London and has a defined boundary with Essex in the middle of the Thames Estuary. The ceremonial county boundaries of Kent include the shire county of Kent and the unitary borough of...

, in 1834 (lower Lower Greensand Formation), which Mantell soon acquired. He was able to identify it as an Iguanodon from its distinctive teeth. The Maidstone slab allowed the first skeletal reconstructions and artistic renderings of Iguanodon. As such, he made some mistakes, the most famous of which was the placement of what he thought was a horn
Horn (anatomy)
A horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae and Bovidae...

 on the nose. The discovery of much better specimens in later years revealed that the horn was actually a modified thumb. Still encased in rock, the Maidstone skeleton is currently displayed at the Natural History Museum
Natural History Museum
The Natural History Museum is one of three large museums on Exhibition Road, South Kensington, London, England . Its main frontage is on Cromwell Road...

 in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

. The borough of Maidstone commemorated this find by adding an Iguanodon as a supporter to their coat of arms
Coat of arms
A coat of arms is a unique heraldic design on a shield or escutcheon or on a surcoat or tabard used to cover and protect armour and to identify the wearer. Thus the term is often stated as "coat-armour", because it was anciently displayed on the front of a coat of cloth...

 in 1949. This specimen has become linked with the name I. mantelli, a species named in 1832 by Christian Erich Hermann von Meyer
Christian Erich Hermann von Meyer
Christian Erich Hermann von Meyer was a German palaeontologist.He was born at Frankfurt am Main.In 1832 von Meyer issued a work entitled Palaeologica, and in course of time he published a series of memoirs on various fossil organic remains: molluscs, crustaceans, fishes and higher vertebrata,...

 in place of I. anglicus, but it actually comes from a different formation
Rock formation
This is a list of rock formations that include isolated, scenic, or spectacular surface rock outcrops. These formations are usually the result of weathering and erosion sculpting the existing rock...

 than the original I. mantelli/I. anglicus material.

At the same time, tension began to build between Mantell and Richard Owen
Richard Owen
Sir Richard Owen, FRS KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...

, an ambitious scientist with much better funding and society connections in the turbulent worlds of Reform Act
Reform Act 1832
The Representation of the People Act 1832 was an Act of Parliament that introduced wide-ranging changes to the electoral system of England and Wales...

–era British politics and science. Owen, a firm creationist
Creationism
Creationism is the religious beliefthat humanity, life, the Earth, and the universe are the creation of a supernatural being, most often referring to the Abrahamic god. As science developed from the 18th century onwards, various views developed which aimed to reconcile science with the Genesis...

, opposed the early versions of evolutionary science
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

 ("transmutationism
Transmutation of species
Transmutation of species was a term used by Jean Baptiste Lamarck in 1809 for his theory that described the altering of one species into another, and the term is often used to describe 19th century evolutionary ideas that preceded Charles Darwin's theory of natural selection...

") then being debated and used what he would soon coin as dinosaurs as a weapon in this conflict. With the paper describing Dinosauria, he scaled down dinosaurs from lengths of over 61 metres (200 ft), determined that they were not simply giant lizards, and put forward that they were advanced and mammal-like, characteristics given to them by God
God
God is the English name given to a singular being in theistic and deistic religions who is either the sole deity in monotheism, or a single deity in polytheism....

; according to the understanding of the time, they could not have been "transmuted" from reptiles to mammal-like creatures.

In 1849, a few years before his death in 1852, Mantell realised that Iguanodon was not a heavy, pachyderm
Pachydermata
Pachydermata is an obsolete order of mammals described by Gottlieb Storr, Georges Cuvier and others, at one time recognized by many systematists...

-like animal, 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
Crystal Palace Dinosaurs
The Crystal Palace Dinosaurs, also known as Dinosaur Court, are a series of sculptures of dinosaurs and extinct mammals located in Crystal Palace, London. Commissioned in 1852 and unveiled in 1854, they were the first dinosaur sculptures in the world, pre-dating the publication of Charles Darwin's...

, and so Owen's vision of the dinosaurs became that seen by the public for decades. With Benjamin Waterhouse Hawkins
Benjamin Waterhouse Hawkins
Benjamin Waterhouse Hawkins was an English sculptor and natural history artist renowned for combining both in his work on the life-size models of dinosaurs in the Crystal Palace Park, Sydenham, south London...

, he had nearly two dozen lifesize sculpture
Sculpture
Sculpture is three-dimensional artwork created by shaping or combining hard materials—typically stone such as marble—or metal, glass, or wood. Softer materials can also be used, such as clay, textiles, plastics, polymers and softer metals...

s of various prehistoric animals built out of concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

 sculpted over a steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 and brick
Brick
A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...

 framework; two Iguanodon, one standing and one resting on its belly, were included. Before the sculpture of the standing Iguanodon was completed, he held a banquet for twenty inside it.

Bernissart


The largest find of Iguanodon remains to date occurred on 28 February 1878 in a coal mine at Bernissart
Bernissart
Bernissart is a Walloon municipality located in the Belgian province of Hainaut. On January 1, 2006 Bernissart had a total population of 11,458. The total area is 43.42 km², which gives a population density of 264 inhabitants per km²....

 in Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

, at a depth of 322 m (1056 ft), when two mineworkers, Jules Créteur and Alphonse Blanchard, accidentally hit on a skeleton that they initially took for petrified wood
Petrified wood
Petrified wood is the name given to a special type of fossilized remains of terrestrial vegetation. It is the result of a tree having turned completely into stone by the process of permineralization...

. With the encouragement of Alphonse Briart
Alphonse Briart
Alphonse Briart was supervisor of the coal mines at Bascoup and Mariemont near Morlanwelz in the Hainaut province of Belgium, and a geologist who studied that region. During the period 1863-1896 he and Francois Cornet published a number of books and papers describing fossils and geological...

, supervisor of mines at nearby Morlanwelz
Morlanwelz
Morlanwelz is a Walloon municipality located in the Belgian province of Hainaut. On January 1, 2006 Morlanwelz had a total population of 18,595. The total area is 20.26 km² which gives a population density of 918 inhabitants per km²...

, Louis de Pauw on 15 May 1878 started to excavate the skeletons and in 1882 Louis Dollo
Louis Dollo
Louis Antoine Marie Joseph Dollo was a French-born Belgian palaeontologist, known for formulating Dollo's law. He graduated as an engineer at École Centrale de Lille in France. In 1878, he supervised the excavation of the famous, multiple Iguanodon find, at Bernissart, Belgium. Recently, the...

 reconstructed them. At least 38 Iguanodon individuals were uncovered, most of which were adults. Many of them went on public display beginning in July 1883 and are still present for viewing; nine are displayed as standing mounts, and nineteen are still in the Museum's underfloor. The exhibit makes an impressive display in the Royal Belgian Institute of Natural Sciences
Royal Belgian Institute of Natural Sciences
The Royal Belgian Institute of Natural Sciences is a museum in the Belgian capital of Brussels dedicated to natural history. Its most important pieces are 30 fossilized Iguanodon skeletons, which were discovered in 1878 in Bernissart. The dinosaur hall of the museum is the world's largest museum...

, in Brussels
Brussels
Brussels , officially the Brussels Region or Brussels-Capital Region , is the capital of Belgium and the de facto capital of the European Union...

. A replica of one of these is on display at the Oxford University Museum of Natural History
Oxford University Museum of Natural History
The Oxford University Museum of Natural History, sometimes known simply as the Oxford University Museum, is a museum displaying many of the University of Oxford's natural history specimens, located on Parks Road in Oxford, England. It also contains a lecture theatre which is used by the...

 and at the Sedgwick Museum
Sedgwick Museum of Earth Sciences
The Sedgwick Museum of Earth Sciences, opened in 1904, is the geology museum of the University of Cambridge in England. It is part of the Department of Earth Sciences and is located on the University's Downing Site in Downing Street, central Cambridge, England.The Sedgwick has a collection of more...

 in Cambridge. Most of the remains were referred to a new species, I. bernissartensis, a larger and much more robust animal than the English remains had yet revealed, but one specimen was referred to the nebulous, gracile I. mantelli (now Dollodon bampingi
Dollodon
Dollodon is a genus of ornithopod dinosaur that lived in the Barremian and possibly the early Aptian ages of the Early Cretaceous Period of Europe. Its remains are known from Belgium , England and possibly Germany...

). The skeletons were some of the first complete dinosaur skeletons known. Found with the dinosaur skeletons were the remains of plants, fish, and other reptiles, including the crocodyliform Bernissartia
Bernissartia
Bernissartia is an extinct genus of crocodyliform that lived in the Early Cretaceous, around 130 million years ago.At only in length, Bernissartia is one of the smallest crocodyliforms that ever lived. It resembled modern species in many respects, and was probably semi-aquatic...

.

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
Pyrite
The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...

 disease". Pyrite crystals in the bones were because of oxidation changing to iron sulphate
Iron(II) sulfate
Iron sulfate or ferrous sulfate is the chemical compound with the formula FeSO4. Known since ancient times as copperas and as green vitriol, the blue-green heptahydrate is the most common form of this material...

 with a greater volume, damaging the remains by causing them to crack and crumble. When in the ground, the bones were isolated by moist clay that prevented this from happening, but when removed into the drier open air, the natural chemical conversion began to occur. To limit this effect, De Pauw immediately, in the mine-gallery, again covered the dug-out fossils with wet clay, sealing them with paper and plaster reinforced by iron rings, forming in total about six hundred transportable blocks with a combined weight of a hundred and thirty tons. In Brussels after opening the plaster he impregnated the bones with boiling gelatine mixed with oil of cloves
Oil of cloves
Oil of cloves, also known as clove oil, is an essential oil from the clove plant, Syzygium aromaticum.* CAS number: 8000-34-8It is a natural analgaesic and antiseptic used primarily in dentistry for its main ingredient eugenol...

 as a preservative
Preservative
A preservative is a naturally occurring or synthetically produced substance that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc. to prevent decomposition by microbial growth or by undesirable chemical changes....

. Removing most of the visible pyrite he then hardened them with hide glue, finishing with a final layer of tin foil
Tin foil
Tin foil, also spelled tinfoil, is a thin foil made of tin. Actual tin foil was superseded by cheaper and more durable aluminium foil after World War II, and aluminium foil is sometimes confused with "tin foil" because of its similarity to the former material.-History:Foil made from a thin leaf of...

. Damages were repaired with papier-mâché
Papier-mâché
Papier-mâché , alternatively, paper-mache, is a composite material consisting of paper pieces or pulp, sometimes reinforced with textiles, bound with an adhesive, such as glue, starch, or wallpaper paste....

. This treatment had the unintended effect of sealing in moisture and extending the period of damage. In 1932 museum director Victor van Straelen
Victor van Straelen
Victor van Straelen was a Belgian conservationist, palaeontologist and carcinologist.Van Straelen was born in Antwerp on 14 June 1889, and worked chiefly as a palaeontologist until his retirement in 1954....

 decided that the specimens had to be completely restored again to safeguard their preservation. The staff at the museum in Brussels from December 1935 to August 1936 treated the problem with a combination of alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

, arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

, and 390 kilograms of shellac
Shellac
Shellac is a resin secreted by the female lac bug, on trees in the forests of India and Thailand. It is processed and sold as dry flakes , which are dissolved in ethyl alcohol to make liquid shellac, which is used as a brush-on colorant, food glaze and wood finish...

. This combination was intended to simultaneously penetrate (alcohol), prevent moulding of (arsenic), and harden (shellac) the fossils. The fossils entered a third round of conservation in 2003: until May 2007 the shellac, hide glue and gelatine were removed and replaced with a polyvinyl acetate
Polyvinyl acetate
Polyvinyl acetate, PVA, PVAc, poly, is a rubbery synthetic polymer with the formula n. It belongs to the polyvinyl esters family with the general formula -[RCOOCHCH2]-...

 impregnation and cyanoacrylate
Cyanoacrylate
Cyanoacrylate is the generic name for cyanoacrylate based fast-acting adhesives such as methyl 2-cyanoacrylate, ethyl-2-cyanoacrylate , and n-butyl cyanoacrylate...

 and epoxy
Epoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....

 glues. Modern treatments of this problem typically involve either monitoring the humidity of fossil storage, or, for fresh specimens, preparing a special coating of polyethylene glycol
Polyethylene glycol
Polyethylene glycol is a polyether compound with many applications from industrial manufacturing to medicine. It has also been known as polyethylene oxide or polyoxyethylene , depending on its molecular weight, and under the tradename Carbowax.-Available forms:PEG, PEO, or POE refers to an...

 that is then heated in a vacuum pump, so moisture is immediately removed and pore space is infiltrated with polyethelene glycol to seal and strengthen the fossil.

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
Cassowary
The cassowaries are ratites, very large flightless birds in the genus Casuarius native to the tropical forests of New Guinea, nearby islands and northeastern Australia. There are three extant species recognized today...

 and wallaby
Wallaby
A wallaby is any of about thirty species of macropod . It is an informal designation generally used for any macropod that is smaller than a kangaroo or wallaroo that has not been given some other name.-Overview:...

, and put the spike that had been on the nose firmly on the thumb
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...

. He was not completely correct, but he also had the disadvantage of being faced with some of the first complete dinosaur remains. A problem that was later recognised was the bend he introduced into the tail
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...

. This organ was more or less straight, as shown by the skeletons he was excavating, and the presence of ossified tendons. In fact, to get the bend in the tail for a more wallaby or kangaroo
Kangaroo
A kangaroo is a marsupial from the family Macropodidae . In common use the term is used to describe the largest species from this family, especially those of the genus Macropus, Red Kangaroo, Antilopine Kangaroo, Eastern Grey Kangaroo and Western Grey Kangaroo. Kangaroos are endemic to the country...

-like posture, the tail would have had to be broken. With its correct, straight tail and back, the animal would have walked with its body held horizontal to the ground, arms in place to support the body if needed.

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
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

, when the town was occupied by German forces
German Empire
The German Empire refers to Germany during the "Second Reich" period from the unification of Germany and proclamation of Wilhelm I as German Emperor on 18 January 1871, to 1918, when it became a federal republic after defeat in World War I and the abdication of the Emperor, Wilhelm II.The German...

, preparations were made to reopen the mine for palaeontology, and Otto Jaekel
Otto Jaekel
Otto Max Johannes Jaekel was a German paleontologist and geologist.Jaekel was born in Neusalz , Prussian Silesia. He studied geology and paleontology in Liegnitz . After graduating in 1883, he moved to Breslau and studied under Ferdinand Roemer until 1885. Karl von Zittel awarded a PhD to Jaekel...

 was sent from Berlin
Berlin
Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...

 to supervise. The Allies
Allies of World War I
The Entente Powers were the countries at war with the Central Powers during World War I. The members of the Triple Entente were the United Kingdom, France, and the Russian Empire; Italy entered the war on their side in 1915...

 recaptured Bernissart just as the first fossiliferous layer was about to be uncovered. Further attempts to reopen the mine were hindered by financial problems and were stopped altogether in 1921 when the mine flooded.

To the present: Worldwide finds


Research on Iguanodon decreased during the early part of the 20th century as World Wars and the Great Depression
Great Depression
The Great Depression was a severe worldwide economic depression in the decade preceding World War II. The timing of the Great Depression varied across nations, but in most countries it started in about 1929 and lasted until the late 1930s or early 1940s...

 enveloped Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

. A new species that would become the subject of much study and taxonomic controversy, I. atherfieldensis, was named in 1925 by R. W. Hooley
Reginald Hooley
Reginald Walter Hooley, born Southampton 5 September 1865, died 5 May 1923, was a businessman and amateur paleontologist collecting on the Isle of Wight. Regular visits to the island resulted in the find of hundreds of fossils among which several major specimens on which he himself from 1900...

, for a specimen collected at Atherfield Point on the Isle of Wight
Isle of Wight
The Isle of Wight is a county and the largest island of England, located in the English Channel, on average about 2–4 miles off the south coast of the county of Hampshire, separated from the mainland by a strait called the Solent...

. However, what had been a European genus was now being found worldwide, with material in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

 (teeth from Tunisia
Tunisia
Tunisia , officially the Tunisian RepublicThe long name of Tunisia in other languages used in the country is: , is the northernmost country in Africa. It is a Maghreb country and is bordered by Algeria to the west, Libya to the southeast, and the Mediterranean Sea to the north and east. Its area...

 and elsewhere in the Sahara
Sahara
The Sahara is the world's second largest desert, after Antarctica. At over , it covers most of Northern Africa, making it almost as large as Europe or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean...

), Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...

 (I. orientalis), and the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 (I. ottingeri from Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

). Another North American species, from South Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

, once assigned to Iguanodon as I. lakotaensis, has since been reclassified as the genus Dakotadon
Dakotadon
Dakotadon is a genus of iguanodont dinosaur from the Barremian-age Lower Cretaceous Lakota Formation of South Dakota, USA, known from a partial skull. It was first described in 1989 as Iguanodon lakotaensis, by David B. Weishampel and Philip R. Bjork. Its assignment has been controversial. Some...

.

Iguanodon was not part of the initial work of the dinosaur renaissance
Dinosaur renaissance
The dinosaur renaissance was a small-scale scientific revolution that started in the late 1960s, and led to renewed academic and popular interest in dinosaurs...

 that began with the description of Deinonychus
Deinonychus
Deinonychus was a genus of carnivorous dromaeosaurid dinosaur. There is one described species, Deinonychus antirrhopus. This 3.4 meter long dinosaur lived during the early Cretaceous Period, about 115–108 million years ago . Fossils have been recovered from the U.S...

 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
David B. Norman
David Bruce Norman is a British paleontologist, currently Director of the Sedgwick Museum, Cambridge University. He is a fellow at Christ's College, Cambridge where he teaches geology in the Natural Sciences tripos. He is a member of the Palaeontological Association. He has studied Iguanodon...

's work on numerous aspects of the genus has made it one of the best-known dinosaurs. In addition, a further find of numerous Iguanodon skeletons, in Nehden, Nordrhein-Westphalen
North Rhine-Westphalia
North Rhine-Westphalia is the most populous state of Germany, with four of the country's ten largest cities. The state was formed in 1946 as a merger of the northern Rhineland and Westphalia, both formerly part of Prussia. Its capital is Düsseldorf. The state is currently run by a coalition of the...

, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, has provided evidence for gregariousness
Herd
Herd refers to a social grouping of certain animals of the same species, either wild or domestic, and also to the form of collective animal behavior associated with this or as a verb, to herd, to its control by another species such as humans or dogs.The term herd is generally applied to mammals,...

 in this genus, as the animals in this areally restricted
Area
Area is a quantity that expresses the extent of a two-dimensional surface or shape in the plane. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat...

 find appear to have been killed by flash flood
Flash flood
A flash flood is a rapid flooding of geomorphic low-lying areas—washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a storm, hurricane, or tropical storm or meltwater from ice or snow flowing over ice sheets or snowfields...

s. At least 15 individuals, from 2 to 8 metres long (6.6 to 26.2 ft), have been found here, although at least some of them are gracile iguanodontians and belong to the related Mantellisaurus
Mantellisaurus
Mantellisaurus is a genus of dinosaur formerly known as Iguanodon atherfieldensis. The new genus was erected by Gregory Paul in 2007. According to Paul, it is more lightly built than Iguanodon and more closely related to Ouranosaurus, making Iguanodon in its traditional sense paraphyletic. It is...

 or Dollodon
Dollodon
Dollodon is a genus of ornithopod dinosaur that lived in the Barremian and possibly the early Aptian ages of the Early Cretaceous Period of Europe. Its remains are known from Belgium , England and possibly Germany...

 (described as I. atherfieldensis, at that time believed to be another species of Iguanodon).

Iguanodon material has also been used in the search for dinosaur DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 and other biomolecule
Biomolecule
A biomolecule is any molecule that is produced by a living organism, including large polymeric molecules such as proteins, polysaccharides, lipids, and nucleic acids as well as small molecules such as primary metabolites, secondary metabolites, and natural products...

s. In research by Graham Embery et al., Iguanodon bones were processed to look for remnant protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s. In this research, identifiable remains of typical bone proteins, such as phosphoprotein
Phosphoprotein
Phosphoproteins are proteins that are physically bonded to a substance containing phosphoric acid . This category of organic molecules includes Fc receptors, Ulks, Calcineurins, K chips, and urocortins....

s and proteoglycan
Proteoglycan
Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan chain. The point of attachment is a Ser residue to which the glycosaminoglycan is joined through a tetrasaccharide bridge...

s, were found in a rib
Rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...

.

Species


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
Megalosaurus
Megalosaurus is a genus of large meat-eating theropod dinosaurs of the Middle Jurassic period of Europe...

 and Pelorosaurus
Pelorosaurus
Pelorosaurus was a huge plant-eating dinosaur. Pelorosaurus was one of the first sauropod dinosaurs ever discovered. Pelorosaurus lived during the Early Cretaceous period, about 138-112 million years ago. Fossils referred to Pelorosaurus have been found in England and Portugal...

), Iguanodon has had a complicated history, and its taxonomy continues to undergo revisions. Remains of the best-known species have come from Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

, and France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

. Remains of similar animals possibly belonging to this genus have been found in Tunisia
Tunisia
Tunisia , officially the Tunisian RepublicThe long name of Tunisia in other languages used in the country is: , is the northernmost country in Africa. It is a Maghreb country and is bordered by Algeria to the west, Libya to the southeast, and the Mediterranean Sea to the north and east. Its area...

 and Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...

, and a distinct species is present in Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

, USA. Gregory Paul has recommended limiting use of I. bernissartensis to the Bernissart finds, and using I. sp. (meaning undetermined species) for robust iguanodontian remains from Barremian
Barremian
The Barremian is an age in the geologic timescale between 130.0 ± 1.5 Ma and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch...

-age rocks of Europe. Thus, after thorough restudy, what had been seen as a quintessentially British dinosaur may in fact be poorly known from England.

I. anglicus was the original type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

, but the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as 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
International Commission on Zoological Nomenclature
The International Commission on Zoological Nomenclature is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 28 members from 20 countries, mainly practicing zoological taxonomists...

 changed the type species to the much better known I. bernissartensis. The original Iguanodon tooth is held at Te Papa Tongarewa
Museum of New Zealand Te Papa Tongarewa
The Museum of New Zealand Te Papa Tongarewa is the national museum and art gallery of New Zealand, located in Wellington. It is branded and commonly known as Te Papa and Our Place; "Te Papa Tongarewa" is broadly translatable as "the place of treasures of this land".The museum's principles...

, the national museum of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 in Wellington
Wellington
Wellington is the capital city and third most populous urban area of New Zealand, although it is likely to have surpassed Christchurch due to the exodus following the Canterbury Earthquake. It is at the southwestern tip of the North Island, between Cook Strait and the Rimutaka Range...

, although it is not on display. The fossil arrived in New Zealand following the move of Gideon Mantell's son Walter there; after the elder Mantell's death, his fossils went to Walter.

Species currently accepted as valid



Only a few of the many species assigned to Iguanodon are still considered to be valid, and only one may fall within the genus Iguanodon. I. bernissartensis, described by George Albert Boulenger
George Albert Boulenger
George Albert Boulenger FRS was a Belgian-British zoologist who identified over 2000 new animal species, chiefly fish, reptiles and amphibians.-Life:...

 in 1881, is the neotype
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 for the genus. This species is best known for the many skeletons discovered in Bernissart, but is also known from remains across Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

. David Norman suggested that it includes the dubious
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...

 Mongolian I. orientalis, but this has not been followed by other researchers.

Reassigned species


Two species of Iguanodon named by Richard Owen have since been reassigned to other genera:
  • I. hoggi (also spelled I. boggii or hoggii), named by Owen for a lower jaw from the Tithonian
    Tithonian
    In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...

    Berriasian
    Berriasian
    In the geological timescale, the Berriasian is an age or stage of the Early or Lower Creteceous. It is the oldest or lowest subdivision in the entire Cretaceous. It spanned between 145.5 ± 4.0 Ma and 140.2 ± 3.0 Ma...

    -age Upper Jurassic
    Late Jurassic
    The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...

    Lower Cretaceous
    Early Cretaceous
    The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

     Purbeck Beds of Dorset
    Dorset
    Dorset , is a county in South West England on the English Channel coast. The county town is Dorchester which is situated in the south. The Hampshire towns of Bournemouth and Christchurch joined the county with the reorganisation of local government in 1974...

     in 1874, has been reassigned to its own genus, Owenodon
    Owenodon
    Owenodon is a genus of iguanodontian dinosaur known from a partial lower jaw discovered in Early Cretaceous-age rocks of Durlston Bay, Dorset, United Kingdom. The specimen, NHM R2998, comes from the Purbeck Limestone, dating to the middle Berriasian stage...

    .
  • I. major, a species named by Justin Delair in 1966, based on a vertebra from the Isle of Wight
    Isle of Wight
    The Isle of Wight is a county and the largest island of England, located in the English Channel, on average about 2–4 miles off the south coast of the county of Hampshire, separated from the mainland by a strait called the Solent...

     originally described by Owen in 1842 as a species of Streptospondylus
    Streptospondylus
    Streptospondylus is a genus of tetanuran theropod dinosaur known from the Middle Jurassic period of France, 161 million years ago. It was a medium-sized predator.-Discovery and naming:...

    , S. major, is a nomen dubium
    Nomen dubium
    In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...

     which is now thought to be a synonym of I. anglicus, although it may be its own species.


Other than the two species described by Owen which have been reassigned to other genera, sixteen other species have since been reclassified:
  • Iguanodon albinus (or Albisaurus scutifer), described by Czech palaeontologist
    Paleontology
    Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...

     Antonin Fritsch
    Antonin Fritsch
    Antonin Fritsch was a Czech paleontologist, biologist and geologist, living during the Austria–Hungary era. Professor at the Charles University and later became director of the National Museum in Prague...

     (correctly Frič) in 1893, is a dubious nondinosaurian reptile
    Reptile
    Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

     now known as Albisaurus albinus
    Albisaurus
    Albisaurus was once thought to be a genus of dinosaur, but is now thought to be a non-dinosaurian archosaur. It was first described by Antonin Fritsch , a Czech palaeontologist, in 1893, but the remains are sparse...

    .
  • I. atherfieldensis, described by R.W. Hooley
    Reginald Hooley
    Reginald Walter Hooley, born Southampton 5 September 1865, died 5 May 1923, was a businessman and amateur paleontologist collecting on the Isle of Wight. Regular visits to the island resulted in the find of hundreds of fossils among which several major specimens on which he himself from 1900...

     in 1925, was smaller and less robust than I. bernissartensis, with longer neural spines. It was renamed Mantellisaurus atherfieldensis
    Mantellisaurus
    Mantellisaurus is a genus of dinosaur formerly known as Iguanodon atherfieldensis. The new genus was erected by Gregory Paul in 2007. According to Paul, it is more lightly built than Iguanodon and more closely related to Ouranosaurus, making Iguanodon in its traditional sense paraphyletic. It is...

     in 2007.
  • I. exogyrarum (also spelled I. exogirarum or I. exogirarus) was described by Fritsch in 1878. It is a nomen dubium based on very poor material and has been reassigned, by George Olshevsky
    George Olshevsky
    George Olshevsky is a freelance editor, writer, publisher, amateur paleontologist, and mathematician living in San Diego, California.Olshevsky maintains the comprehensive online Dinosaur Genera List...

    , to Ponerosteus
    Ponerosteus
    Ponerosteus is a dubious genus of archosaur which was first identified as "Iguanodon exogirarum" by Antonin Fritsch in 1878 for a specimen from the Cenomanian . He later renamed it Procerosaurus, unaware that this name was already in use...

    .
  • I. valdensis, a species named by Ernst van den Broeck in 1900. Originally named Vectisaurus by Hulke in 1879 based on vertebral and pelvic
    Pelvis
    In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...

     remains, it was from the Barremian
    Barremian
    The Barremian is an age in the geologic timescale between 130.0 ± 1.5 Ma and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch...

     stage of the Isle of Wight. It may be a partially grown specimen of Mantellisaurus atherfieldensis, or from an undetermined species of Mantellisaurus.
  • I. gracilis, named by Lydekker in 1888 as the type species of Sphenospondylus and assigned to Iguanodon in 1969 by Rodney Steel, may belong to Mantellisaurus atherfieldensis.


Two species described by Richard Lydekker
Richard Lydekker
Richard Lydekker was an English naturalist, geologist and writer of numerous books on natural history.-Biography:...

 in the late 19th century have been reassigned to different genera.
  • I. dawsoni, described by Lydekker in 1888, is known from two partial skeletons found in East Sussex
    East Sussex
    East Sussex is a county in South East England. It is bordered by the counties of Kent, Surrey and West Sussex, and to the south by the English Channel.-History:...

    , England
    England
    England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

    , from the middle Valanginian
    Valanginian
    In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 140.2 ± 3.0 Ma and 136.4 ± 2.0 Ma...

    -age Lower Cretaceous
    Early Cretaceous
    The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

     Wadhurt Clay. It is now the type species of Barilium
    Barilium
    Barilium is a genus of iguanodontian dinosaur which was first described as a species of Iguanodon by Richard Lydekker in 1888, the specific epithet honouring the discoverer Charles Dawson....

    .
  • I. fittoni was described by Lydekker in 1889. Like I. dawsoni, this species was described from the Wadhurst Clay of East Sussex. It is now the type species of Hypselospinus
    Hypselospinus
    Hypselospinus is a genus of iguanodontian dinosaur which was first described as a species of Iguanodon by Richard Lydekker in 1889, the specific name honouring William Henry Fitton....

    .

  • I. foxii (also spelled I. foxi) was originally described by Thomas Henry Huxley in 1869 as the type species of Hypsilophodon; Owen (1873 or 1874) reassigned it to Iguanodon, but his assignment was soon overturned.
  • I. hollingtoniensis (also spelled I. hollingtonensis), described by Lydekker in 1889, is a synonym of I. fittoni. A specimen assigned to I. hollingtoniensis and I. mantelli over the years has an unusual combination of hadrosaurid-like lower jaw and very robust forelimb, and may represent an unnamed taxon.
  • I. prestwichii (also spelled I. prestwichi), described by John Hulke
    John Hulke
    John Whitaker Hulke FRCS FRS FGS was a British surgeon, geologist and fossil collector. He was the son of a physician in Deal, who became a Huxleyite despite being deeply religious....

     in 1880, has been reassigned to Camptosaurus prestwichii
    Camptosaurus
    Camptosaurus is a genus of plant-eating, beaked ornithischian dinosaurs of the Late Jurassic period of western North America. The name means 'flexible lizard', ....

     or to its own genus Cumnoria
    Cumnoria
    Cumnoria is a genus of herbivorous iguanodontian dinosaur. It is a basal iguanodontian which lived during the upper Jurassic period in what is now Oxfordshire, United Kingdom....

    .
  • I. seelyi (also incorrectly spelled I. seeleyi), described by Hulke two years after I. prestwichii, has been synonymised with Dollodon bampingi, though this is controversial.
  • I. suessii, described by Emanuel Bunzel
    Emanuel Bunzel
    Emanuel Bunzel, born 1828, was an Austrian paleontologist.In 1871, he described a skull fragment found in an Austrian coal mine years before by colleagues Ferdinand Stoliczka and Eduard Suess as the type specimen for the dinosaur genus Struthiosaurus, the first discovered in the region. Another...

     in 1871, has been reassigned to Mochlodon suessi
    Mochlodon
    Mochlodon is a genus of iguanodont dinosaur from the Late Cretaceous.In 1859 coal mine administrator Pawlowitsch notified the University of Vienna that some fossils had been found in the Gute Hoffnung mine at Muthmannsdorf in Austria...

    .

  • I. lakotaensis was described by David B. Weishampel and Philip R. Bjork
    Philip R. Bjork
    Philip Reese Bjork is an American geologist and paleontologist known for his work in unearthing dinosaur species in America.-Career:Bjork received his undergraduate degree at the University of Michigan...

     in 1989. The only well-accepted North America
    North America
    North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

    n species of Iguanodon, I. lakotaensis was described from a partial skull from the Barremian
    Barremian
    The Barremian is an age in the geologic timescale between 130.0 ± 1.5 Ma and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch...

    -age Lower Cretaceous
    Early Cretaceous
    The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

     Lakota Formation
    Lakota Formation
    The Lakota Formation is a sequence of rocks from the Barremian epoch from Western North America. Located in South Dakota, the name is derived from the Lakota Native American tribe....

     of South Dakota
    South Dakota
    South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

    . Its assignment has been controversial. Some researchers suggest that it was more basal
    Basal (phylogenetics)
    In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

     than I. bernissartensis, and related to Theiophytalia
    Theiophytalia
    Theiophytalia is a genus of herbivorous iguanodontian dinosaur from the lower Cretaceous period of Colorado.-Etymology:...

    , but David Norman has suggested that it was a synonym
    Synonym (taxonomy)
    In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...

     of I. bernissartensis. Gregory S. Paul
    Gregory S. Paul
    Gregory Scott Paul is a freelance researcher, author and illustrator who works in paleontology, and more recently has examined sociology and theology. He is best known for his work and research on theropod dinosaurs and his detailed illustrations, both live and skeletal...

     has since given the species its own genus, Dakotadon
    Dakotadon
    Dakotadon is a genus of iguanodont dinosaur from the Barremian-age Lower Cretaceous Lakota Formation of South Dakota, USA, known from a partial skull. It was first described in 1989 as Iguanodon lakotaensis, by David B. Weishampel and Philip R. Bjork. Its assignment has been controversial. Some...

    .

  • Iguanodon mantelli (also spelled I. manteli or I. mantellii), described by Christian Erich Hermann von Meyer
    Christian Erich Hermann von Meyer
    Christian Erich Hermann von Meyer was a German palaeontologist.He was born at Frankfurt am Main.In 1832 von Meyer issued a work entitled Palaeologica, and in course of time he published a series of memoirs on various fossil organic remains: molluscs, crustaceans, fishes and higher vertebrata,...

     in 1832, was originally based on the same material as I. anglicus. Several skeletons, however, including the Maidstone specimen — later made the lectotype
    Lectotype
    In botanical nomenclature and zoological nomenclature, a lectotype is a kind of name-bearing type. When a species was originally described on the basis of a name-bearing type consisting of multiple specimens, one of those may be designated as the lectotype...

     — and one of the Bernissart skeletons have been assigned here over the years, and their attribution is not complete. The gracile Bernissart skeleton, for example, has been reassigned, first to Mantellisaurus atherfieldensis, and upon further review, to its own genus and species, Dollodon bampingi
    Dollodon
    Dollodon is a genus of ornithopod dinosaur that lived in the Barremian and possibly the early Aptian ages of the Early Cretaceous Period of Europe. Its remains are known from Belgium , England and possibly Germany...

    . However, some authorities have continued to consider Dollodon a synonym of Mantellisaurus.
  • I. orientalis, described by A. K. Rozhdestvensky
    Anatoly Konstantinovich Rozhdestvensky
    Anatoly Konstantinovich Rozhdestvensky was a Russian paleontologist responsible for naming many dinosaurs, including Aralosaurus and Probactrosaurus....

     in 1952, was based on poor material, but a skull with a distinctive arched snout that had been assigned to it was renamed Altirhinus kurzanovi
    Altirhinus
    Altirhinus is a genus of iguanodontian ornithopod dinosaur from the Early Cretaceous Period of Mongolia.-Description:Altirhinus was herbivorous and bipedal when walking or running, but probably became quadrupedal when feeding from the ground. According to the original description, the entire body...

     in 1998. At the same time, I. orientalis was considered to be a nomen dubium because it cannot be compared to I. bernissartensis.
  • Harry Seeley
    Harry Seeley
    Harry Govier Seeley was a British paleontologist.-Career:Seeley was born in London, the son of Richard Hovill Seeley, goldsmith, and his second wife Mary Govier. He attended classes at the Royal School of Mines, Kensington before becoming an assistant to Adam Sedgwick at the Woodwardian Museum,...

     described I. phillipsi in 1869, but later reassigned it to Priodontognathus
    Priodontognathus
    Priodontognathus was a genus of ankylosaurian dinosaur possibly from the Oxfordian-age Upper Jurassic Lower Calcareous Grit of Yorkshire, England...

    .

Delapparentia
Delapparentia
Delapparentia is a genus of iguanodont dinosaur from the Early Cretaceous period of Galve, Teruel Province, Spain.The type specimen, MPT/I.G, was found in the Spring of 1958 by amateur palaeontologist José María Herrero Marzo...

 turolensis was named in 2011
2011 in paleontology
-Lobopods:-Arachnids:-Insects:-Newly named jawless vertebrates:-Newly named acanthodian:-Newly named cartilaginous fishes:-Newly named bony fishes:-Newly named lepospondyls:-Newly named temnospondyls:-Newly named lissamphibians:...

 based on a specimen previously assigned to Iguanodon bernissartensis

Dubious species


Five Iguanodon species are considered to be nomina dubia or undescribed:
  • I. anglicus, described by Friedrich Holl in 1829, is the original type species of Iguanodon, but, as discussed above, was replaced by I. bernissartensis. In the past, it has been spelled as I. angelicus (Lessem and Glut, 1993) and I. anglicum (Holl, 1829 emend. Bronn, 1850). It is known from teeth from the middle Valanginian
    Valanginian
    In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 140.2 ± 3.0 Ma and 136.4 ± 2.0 Ma...

    -age Lower Cretaceous
    Early Cretaceous
    The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

     Tilgate Forest (Grinstead Clay Formation) of East Sussex
    East Sussex
    East Sussex is a county in South East England. It is bordered by the counties of Kent, Surrey and West Sussex, and to the south by the English Channel.-History:...

    , England.
  • I. hillii, coined by Edwin Tully Newton in 1892 for a tooth from the early Cenomanian
    Cenomanian
    The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...

     Upper Cretaceous
    Late Cretaceous
    The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

     Lower Chalk of Hertfordshire
    Hertfordshire
    Hertfordshire is a ceremonial and non-metropolitan county in the East region of England. The county town is Hertford.The county is one of the Home Counties and lies inland, bordered by Greater London , Buckinghamshire , Bedfordshire , Cambridgeshire and...

    , is an early hadrosaurid
    Hadrosaurid
    Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

     of some sort.
  • "I. mongolensis" (Whitfield, 1992) is a nomen nudum
    Nomen nudum
    The phrase nomen nudum is a Latin term, meaning "naked name", used in taxonomy...

     from a photo caption in a book, of remains that would later be named Altirhinus.

  • I. ottingeri, described by Peter Galton
    Peter Galton
    Peter M. Galton is a British vertebrate paleontologist working in America, who has to date written or co-written about a hundred papers in scientific journals or chapters in paleontology textbooks, especially on ornithischian and prosauropod dinosaurs.With Robert Bakker in a joint article...

     and James A. Jensen
    James A. Jensen
    James A. Jensen , was an American paleontologist. His extensive collecting program at BYU in the Utah-Colorado region which spanned 23 years was comparable in terms of the number of specimens collected to that of Barnum Brown during the early 20th century. He was given the name "Dinosaur Jim"...

     in 1979, is a nomen dubium based on teeth from the possibly Aptian
    Aptian
    The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...

    -age lower Cedar Mountain Formation of Utah.
  • I. praecursor (also spelled I. precursor), described by E. Sauvage in 1876 from teeth from an unnamed Kimmeridgian
    Kimmeridgian
    In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma . The Kimmeridgian follows the Oxfordian and precedes the Tithonian....

     (Late Jurassic
    Late Jurassic
    The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...

    ) formation in Pas-de-Calais, France
    France
    The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

    , is actually a sauropod
    Sauropoda
    Sauropoda , or the sauropods , are an infraorder of saurischian dinosaurs. They had long necks, long tails, small heads , and thick, pillar-like legs. They are notable for the enormous sizes attained by some species, and the group includes the largest animals to have ever lived on land...

    , sometimes assigned to Neosodon
    Neosodon
    Neosodon was a genus of sauropod dinosaur from the Late Tithonian-age Upper Jurassic Sables et Grès à Trigonia gribosa of Départment du Pas-de-Calais, France. It has never been formally given a species name, but is often seen as N. praecursor, which actually comes from a different animal...

    , although the two come from different formations.


Finally, several other poorly known genera and species are included with Iguanodon without being separately named species of that genus, although their assignment is less certain with the renaming of I. atherfieldensis. These include the species "Streptospondylus" recentior (Owen, 1851), "Cetiosaurus
Cetiosaurus
Cetiosaurus meaning 'whale lizard', from the Greek cetus/κητος meaning 'sea monster' and saurus/σαυρος meaning 'lizard', was a sauropod dinosaur from the Mid to Late Jurassic Period in what are now Europe and Africa. It is estimated to have been about long and to have weighed roughly...

" brachyurus, and part of "C." brevis (Owen, 1842; "C." brevis is a chimera
Chimera (paleontology)
In paleontology, a chimera is a fossil which was reconstructed with elements coming from more than a single species of animal. A now classic example of chimera is Protoavis.-List of paleontological chimeras:*Brontosaurus*Lametasaurus...

). The nomen nudum "Proiguanodon" (van den Broeck, 1900) also belongs here, and possibly the very obscure "Streptospondylus" grandis (Owen, 1851) and meyeri (Owen, 1854). The genera Iguanosaurus (Ritgen, 1828), Hikanodon (Keferstein, 1834), and Therosaurus (Fitzinger, 1840), are simply junior objective synonyms, later names for the material of I. anglicus.

Feeding and diet



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 symphysis
Symphysis menti
The external surface of the mandible is marked in the median line by a faint ridge, indicating the symphysis menti, mandibular symphysis, or line of junction of the two pieces of which the bone is composed at an early period of life....

, which he found best compared to that of the two-toed sloth
Two-toed sloth
Choloepus is a genus of mammals of Central and South America, within the family Megalonychidae consisting of two-toed sloths. There are only two species of Choloepus : Linnaeus's Two-toed Sloth and Hoffmann's Two-toed Sloth...

 and the extinct
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 ground sloth Mylodon
Mylodon
Mylodon is an extinct genus of giant ground sloth that lived in the Patagonia area of South America until roughly 10,000 years ago.Mylodon weighed about and stood up to tall when raised up on its hind legs. Preserved dung has shown it was a herbivore. It had very thick hide and had osteoderms...

. He also suggested that Iguanodon had a prehensile
Prehensility
Prehensility is the quality of an appendage or organ that has adapted for grasping or holding. The word is derived from the Latin term prehendere, meaning "to grasp."-Examples:Appendages that can become prehensile include:...

 tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

 which could be used to gather food, like a giraffe
Giraffe
The giraffe is an African even-toed ungulate mammal, the tallest of all extant land-living animal species, and the largest ruminant...

. More complete remains have shown this to be an error; for example, the hyoid bone
Hyoid bone
The hyoid bone is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies at the level of the base of the mandible in the front and the third cervical vertebra behind.Unlike other bones, the hyoid is only distantly...

s that supported the tongue are heavily built, implying a muscular, non-prehensile tongue used for moving food around in the mouth. The giraffe-tongue idea has also been incorrectly attributed to Dollo via a broken lower jaw.

Iguanodon teeth are, as the name suggests, like those of an iguana, but larger. Unlike hadrosaurid
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

s, which had columns of replacement teeth, Iguanodon only had one replacement tooth at a time for each position. The upper jaw
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...

 held up to 29 teeth per side, with none at the front of the jaw
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....

, and the lower jaw
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...

 25; the numbers differ because teeth in the lower jaw are broader than those in the upper. Because the tooth rows are deeply inset from the outside of the jaws, and because of other anatomical details, it is believed that, as with most other ornithischians, Iguanodon had some sort of cheek
Cheek
Cheeks constitute the area of the face below the eyes and between the nose and the left or right ear. They may also be referred to as jowls. "Buccal" means relating to the cheek. In humans, the region is innervated by the buccal nerve...

-like structure, muscular or non-muscular, to retain food in the mouth.

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 equivalent of mammalian chewing
Mastication
Mastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion and it increases the surface area of foods to allow more efficient break down by enzymes. During the mastication process, the food is positioned between the teeth for grinding by...

. Because the teeth were always replaced, the animal could have used this mechanism throughout its life, and could eat tough plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

 material. Additionally, the front ends of the animal's jaws were toothless and tipped with bony nodes, both upper and lower, providing a rough margin that was likely covered and lengthened by a keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...

ous material to form a cropping beak for biting off twig
Twig
A twig is a small thin terminal branch of a woody plant. Twigs are critically important in identification of trees, shrubs and vines, especially in wintertime. The buds on the twig are an important diagnostic characteristic, as are the abscission scars where the leaves have fallen away...

s and shoot
Shoot
Shoots are new plant growth, they can include stems, flowering stems with flower buds, and leaves. The new growth from seed germination that grows upward is a shoot where leaves will develop...

s. Its food gathering would have been aided by its flexible little finger
Little finger
The little finger, often called the pinky in American English, pinkie in Scottish English , or small finger in medicine, is the most ulnar and usually smallest finger of the human hand, opposite the thumb, next to the ring finger.-Muscles:There are four muscles that...

, which could have been used to manipulate objects, unlike the other fingers.

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
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

 foliage
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 at 4–5 metres high (13–16.5 ft). A diet of horsetails, cycad
Cycad
Cycads are seed plants typically characterized by a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female . Cycads vary in size from having a trunk that is only a few centimeters...

s, and conifers
Pinophyta
The conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 division level taxa within the Kingdom Plantae. Pinophytes are gymnosperms. They are cone-bearing seed plants with vascular tissue; all extant conifers are woody plants, the great majority being...

 was suggested by David Norman, although iguanodonts in general have been tied to the advance of angiosperm
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...

 plants in the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 due to the dinosaurs' inferred low browsing habits. Angiosperm growth, according to this hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...

, would have been encouraged by iguanodont feeding because gymnosperms would be removed, allowing more space for the weed
Weed
A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...

-like early angiosperms to grow. The evidence is not conclusive, though. Whatever its exact diet, due to its size and abundance, Iguanodon is regarded as a dominant medium to large herbivore for its ecological communities
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

. In England, this included the small predator Aristosuchus
Aristosuchus
Aristosuchus was a small coelurosaurian dinosaur, whose name was derived from the Greek ἄριστος and σουχος, the Ancient Greek corruption of the name of the Egyptian crocodile-headed god Sobek. It shared many characteristics with birds.Aristosuchus was a bipedal, meat-eating theropod dinosaur...

, larger predators Eotyrannus
Eotyrannus
Eotyrannus was a genus of tyrannosauroid theropod dinosaur hailing from the Early Cretaceous Wessex Formation beds, included in Wealden Group, located in the southwest coast of the Isle of Wight, United Kingdom...

, Baryonyx
Baryonyx
Baryonyx is a genus of carnivorous saurischian dinosaur first discovered in clay pits just south of Dorking, England, and later reported from fossils found in northern Spain and Portugal. It is known to contain only one species, Baryonyx walkeri...

, and Neovenator
Neovenator
Neovenator is a genus of allosauroid dinosaur. Since its discovery on the Isle of Wight, UK, it has become one of the best-known large carnivorous dinosaurs in Europe. Neovenator was at first considered possibly a new species of Megalosaurus. It measured approximately 7.5 meters in length,...

, low-feeding herbivores Hypsilophodon
Hypsilophodon
Hypsilophodon is an ornithopod dinosaur genus from the Early Cretaceous period of Europe. It was a small bipedal animal with an herbivorous or possibly omnivorous diet...

 and Valdosaurus
Valdosaurus
Valdosaurus is a genus of bipedal herbivorous iguanodont ornithopod dinosaur found on the Isle of Wight and elsewhere in England. It lived during the Early Cretaceous.-Discovery and naming:...

, fellow "iguanodontid" Mantellisaurus, the armoured
Armour (zoology)
Armour in animals is external or superficial protection against attack by predators, formed as part of the body , usually through the hardening of body tissues, outgrowths or secretions. It has therefore mostly developed in 'prey' species...

 herbivore Polacanthus
Polacanthus
Polacanthus, deriving its name from the Ancient Greek poly-/πολυ- "many" and acantha/ακανθα "thorn" or "prickle", was an early armored, spiked, plant-eating ankylosaur from the early Cretaceous period. Early depictions often gave it a very vague head as it was only known from the rear half of the...

, and sauropods like Pelorosaurus
Pelorosaurus
Pelorosaurus was a huge plant-eating dinosaur. Pelorosaurus was one of the first sauropod dinosaurs ever discovered. Pelorosaurus lived during the Early Cretaceous period, about 138-112 million years ago. Fossils referred to Pelorosaurus have been found in England and Portugal...

.

Posture and movement



Early fossil remains were fragmentary, which led to much speculation on the posture and nature of Iguanodon. As discussed, 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 was of the opinion it was a stumpy creature with four pillar-like legs. The job of overseeing the first lifesize reconstruction of dinosaurs was initially offered to Mantell, who declined due to poor health, and Owen's vision subsequently formed the basis on which the sculptures took shape. Its bipedal nature was revealed with the discovery of the Bernissart skeletons. However, it was depicted in an upright posture, with the tail dragging along the ground, acting as the third leg of a tripod.

During his re-examination of Iguanodon, David Norman was able to show that this posture was unlikely, due to the presence of a long tail 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 pectoral girdle more understandable. For example, the hand is relatively immobile, with the three central fingers grouped together, bearing hoof
Hoof
A hoof , plural hooves or hoofs , is the tip of a toe of an ungulate mammal, strengthened by a thick horny covering. The hoof consists of a hard or rubbery sole, and a hard wall formed by a thick nail rolled around the tip of the toe. The weight of the animal is normally borne by both the sole...

-like phalanges
Phalanx bones
In anatomy, phalanx bones are those that form the fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones.The phalanges do not have individual names...

, and able to hyperextend
Extension (kinesiology)
In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...

. This would have allowed them to bear weight. The wrist
Wrist
In human anatomy, the wrist is variously defined as 1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand;...

 is also relatively immobile, and the arms and shoulder bones robust. These features all suggest that the animal spent time on all fours.

Furthermore, it appears that Iguanodon became more quadrupedal as it got older and heavier; juvenile
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...

 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 palm
Hand
A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...

s faced each other, as shown by iguanodontian trackways and the anatomy of this genus's arms and hands. The three toed pes
Pes (zoology)
The pes is the zoological term for the distal portion of the hind limb of tetrapod animals. It is the part of the pentadactyl limb that includes the metatarsals and digits . During evolution, it has taken many forms and served a variety of functions...

 (foot) of Iguanodon was relatively long, and when walking, both the hand and the foot would have been used in a digitigrade
Digitigrade
A digitigrade is an animal that stands or walks on its digits, or toes. Digitigrades include walking birds , cats, dogs, and many other mammals, but not plantigrades or unguligrades...

 fashion (on the fingers and toes). The maximum speed of Iguanodon has been estimated at 24 km/h (14.9 mph), which would have been as a biped; it would not have been able to gallop as a quadruped.

Large three-toed footprints are known in Early Cretaceous rocks of England, particularly Wealden
Wealden
For the stone, see Wealden GroupWealden is a local government district in East Sussex, England: its name comes from the Weald, the area of high land which occupies the centre of its area.-History:...

 beds on the Isle of Wight, and these trace fossil
Trace fossil
Trace fossils, also called ichnofossils , are geological records of biological activity. Trace fossils may be impressions made on the substrate by an organism: for example, burrows, borings , urolites , footprints and feeding marks, and root cavities...

s 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
Ichnotaxon
An ichnotaxon is defined by the International Code of Zoological Nomenclature as "a taxon based on the fossilized work of an organism", that is, the non-human equivalent of an artifact. Ichnotaxa are names used to identify and distinguish morphologically distinctive ichnofossils, more commonly...

 he named Iguanodon, and Samuel Beckles
Samuel Beckles
Samuel H. Beckles was an English 19th century dinosaur hunter, who collected remains in Sussex and the Isle of Wight. In 1854 he described bird-like trackways that he thought could have been made by dinosaurs, which he later identified as probably those of an Iguanodon in 1862...

 noted in 1854 that they looked like bird tracks, but might have come from dinosaurs. The identity of the trackmakers was greatly clarified upon the discovery in 1857 of the hind leg of a young Iguanodon, with distinctly three-toed feet, showing that such dinosaurs could have made the tracks. Despite the lack of direct evidence, these tracks are often attributed to Iguanodon. A trackway in England shows what may be an Iguanodon moving on all fours, but the foot prints are poor, making a direct connection difficult. Tracks assigned to the ichnogenus Iguanodon are known from locations including places in Europe where the body fossil Iguanodon is known, to Spitsbergen
Spitsbergen
Spitsbergen is the largest and only permanently populated island of the Svalbard archipelago in Norway. Constituting the western-most bulk of the archipelago, it borders the Arctic Ocean, the Norwegian Sea and the Greenland Sea...

, Svalbard
Svalbard
Svalbard is an archipelago in the Arctic, constituting the northernmost part of Norway. It is located north of mainland Europe, midway between mainland Norway and the North Pole. The group of islands range from 74° to 81° north latitude , and from 10° to 35° east longitude. Spitsbergen is the...

, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

.

Thumb spike



The thumb spike is one of the most well-known features of Iguanodon. Although it was originally placed on the animal's nose by Mantell, the complete Bernissart specimens allowed Dollo to correctly place it on the hand, as a modified thumb. (This would not be the last time a dinosaur's modified thumb claw would be misinterpreted; Noasaurus
Noasaurus
Noasaurus is the name given to a carnivorous dinosaur genus of the late Campanian-Maastrichtian...

, Baryonyx
Baryonyx
Baryonyx is a genus of carnivorous saurischian dinosaur first discovered in clay pits just south of Dorking, England, and later reported from fossils found in northern Spain and Portugal. It is known to contain only one species, Baryonyx walkeri...

, and Megaraptor
Megaraptor
Megaraptor is a genus of large theropod dinosaur that lived in the Coniacian stage of the Late Cretaceous. Its fossils have been discovered in the Patagonian region of Argentina...

 are examples since the 1980s where an enlarged thumb claw was first put on the foot, as in dromaeosaurids
Dromaeosauridae
Dromaeosauridae is a family of bird-like theropod dinosaurs. They were small- to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek dromeus meaning 'runner' and sauros meaning 'lizard'...

.)

This thumb is typically interpreted as a close-quarter stiletto
Stiletto
A stiletto is a knife or dagger with a long slender blade and needle-like point, intended primarily as a stabbing weapon. The stiletto blade's narrow cross-section and acuminated tip reduces friction upon entry, allowing the blade to penetrate deeply...

-like weapon against predators, although it could also have been used to break into seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s and fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

s, or against other Iguanodon. One author has suggested that the spike was attached to a venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...

 gland, but this has not been accepted, as the spike was not hollow, nor were there any grooves on the spike for conducting venom.

Possible social behaviour


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 span (?10–100 years), this does not necessarily mean these Iguanodon were herd
Herd
Herd refers to a social grouping of certain animals of the same species, either wild or domestic, and also to the form of collective animal behavior associated with this or as a verb, to herd, to its control by another species such as humans or dogs.The term herd is generally applied to mammals,...

ing animals.

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, more even mix of Dollodon or Mantellisaurus to Iguanodon bernissartensis, and confined geographic nature, may record mortality of herding animals migrating through rivers.

Unlike other purported herding dinosaurs (especially hadrosaurs and ceratopsids
Ceratopsidae
Ceratopsidae is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus...

), there is no evidence that Iguanodon was sexually dimorphic
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

, with one gender
Gender
Gender is a range of characteristics used to distinguish between males and females, particularly in the cases of men and women and the masculine and feminine attributes assigned to them. Depending on the context, the discriminating characteristics vary from sex to social role to gender identity...

 appreciably different from the other. At one time, it was suggested that the Bernissart I. "mantelli", or I. atherfieldensis (Dollodon and Mantellisaurus, respectively) represented a gender, possibly female
Female
Female is the sex of an organism, or a part of an organism, which produces non-mobile ova .- Defining characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...

, of the larger and more robust, possibly male
Male
Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...

, I. bernissartensis. However, this is not supported today.

In popular culture



Since its description in 1825, Iguanodon has been a feature of worldwide popular culture
Popular culture
Popular culture is the totality of ideas, perspectives, attitudes, memes, images and other phenomena that are deemed preferred per an informal consensus within the mainstream of a given culture, especially Western culture of the early to mid 20th century and the emerging global mainstream of the...

. Two lifesize reconstructions of Iguanodon built at the Crystal Palace in London in 1852 greatly contributed to the popularity of the genus. Their thumb spikes were mistaken for horns, and they were depicted as elephant-like quadrupeds, yet this was the first time an attempt was made at constructing full-size dinosaur models.

Several motion pictures have featured Iguanodon. In the Disney film Dinosaur
Dinosaur (film)
Dinosaur is a 2000 American computer-animated film produced by Walt Disney Feature Animation and released by Walt Disney Pictures on May 19, 2000, and is the 39th animated feature in the Walt Disney Animated Classics series...

, an Iguanodon named Aladar served as the protagonist with three other iguanodonts as other main characters; a loosely related ride of the same name at Disney's Animal Kingdom
Disney's Animal Kingdom
Disney's Animal Kingdom is an animal theme park located at the Walt Disney World Resort. The fourth park built at the resort, it opened on April 22, 1998, and it is the largest single Disney theme park in the world, covering more than . It is also the first Disney theme park to be themed entirely...

 is based around bringing an Iguanodon back to the present. Iguanodon is one of the three dinosaur genera that inspired Godzilla
Godzilla
is a daikaijū, a Japanese movie monster, first appearing in Ishirō Honda's 1954 film Godzilla. Since then, Godzilla has gone on to become a worldwide pop culture icon starring in 28 films produced by Toho Co., Ltd. The monster has appeared in numerous other media incarnations including video games,...

; the other two were Tyrannosaurus
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...

 and Stegosaurus
Stegosaurus
Stegosaurus is a genus of armored stegosaurid dinosaur. They lived during the Late Jurassic period , some 155 to 150 million years ago in what is now western North America. In 2006, a specimen of Stegosaurus was announced from Portugal, showing that they were present in Europe as well...

. Iguanodon has also made appearances in some of the many Land Before Time
The Land Before Time (series)
The Land Before Time is a series of animated films centered on dinosaurs. The series began in 1988 with The Land Before Time, directed and produced by Don Bluth and executive produced by George Lucas and Steven Spielberg. It was followed by a total of 12 direct-to-video sequels, though none...

 films, as well as episodes of the television series
The Land Before Time (TV series)
The Land Before Time is an animated television series, based on characters from The Land Before Time film series created by Judy Freudberg and Tony Geiss. It was developed for television by Ford Riley for Universal Animation Studios and Amblin Entertainment , and first premiered on YTV in Canada...

.

Aside from appearances on the silver screen, Iguanodon has also been featured on the television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

 documentary miniseries Walking with Dinosaurs
Walking with Dinosaurs
Walking with Dinosaurs is a six-part documentary television miniseries that was produced by BBC, narrated by Kenneth Branagh, and first aired in the United Kingdom, in 1999. The series was subsequently aired in North America on the Discovery Channel in 2000, with Branagh's voice replaced with that...

 (1999) produced by the BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...

, and played a starring role in Sir Arthur Conan Doyle
Arthur Conan Doyle
Sir Arthur Ignatius Conan Doyle DL was a Scottish physician and writer, most noted for his stories about the detective Sherlock Holmes, generally considered a milestone in the field of crime fiction, and for the adventures of Professor Challenger...

's book, The Lost World as well as featuring in an episode of the Discovery Channel
Discovery Channel
Discovery Channel is an American satellite and cable specialty channel , founded by John Hendricks and distributed by Discovery Communications. It is a publicly traded company run by CEO David Zaslav...

 documentary, Dinosaur Planet. It also was present in Bob Bakker's Raptor Red
Raptor Red
Raptor Red is a 1995 American novel by paleontologist Robert T. Bakker. The book is a third-person account of dinosaurs during the Cretaceous Period, told from the point of view of Raptor Red, a female Utahraptor...

 (1995), as a Utahraptor
Utahraptor
Utahraptor is a genus of theropod dinosaurs, including the largest known members of the family Dromaeosauridae. Fossil specimens date to the upper Barremian stage of the early Cretaceous period...

 prey item. A main belt
Asteroid belt
The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets...

 asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...

, , has been named 9941 Iguanodon
9941 Iguanodon
9941 Iguanodon is an S-type main belt asteroid which orbits the Sun every 3.49 years.It was discovered on February 4, 1989 by Eric Elst at the European Southern Observatory and given the provisional designation "". It was later renamed "Iguanodon" after the dinosaur genus Iguanodon.-References:...

 in honour of the genus.

Because it is both one of the first dinosaurs described and one of the best-known dinosaurs, Iguanodon has been well-placed as a barometer
Barometer
A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term changes in the weather...

 of changing public and scientific perceptions on dinosaurs. Its reconstructions have gone through three stages: the elephant
Elephant
Elephants are large land mammals in two extant genera of the family Elephantidae: Elephas and Loxodonta, with the third genus Mammuthus extinct...

ine quadrupedal horn-snouted reptile of the Victorians
Victorian era
The Victorian era of British history was the period of Queen Victoria's reign from 20 June 1837 until her death on 22 January 1901. It was a long period of peace, prosperity, refined sensibilities and national self-confidence...

; a bipedal but still fundamentally reptilian animal using its tail to prop itself up; and finally, its current, more agile and dynamic representation, able to shift from two legs to all fours. The second representation dominated the early 20th century, but was slowly overturned during the 1960s.

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