Distinctive features include large thumb spikes, which were possibly used for defense against predators, combined with long prehensile fifth fingers able to forage for food.

In the early 21st century it became understood that the remains referred to as Iguanodon in England belonged to four different species (including I. bernissartensis) that were not closely related to each other, which were subsequently split off into Mantellisaurus, Barilium and Hypselospinus.

The story goes that Gideon Mantell's wife, Mary Ann, discovered the first teeth[4] of an Iguanodon in the strata of Tilgate Forest in Whitemans Green, Cuckfield, Sussex, England, in 1822 while her husband was visiting a patient.

However, in 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 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.

The Maidstone slab (NHMUK PV OR 3791) was used in the first skeletal reconstructions and artistic renderings of Iguanodon, but due to its incompleteness, Mantell made some mistakes, the most famous of which was the placement of what he thought was a horn on the nose.

Mantellisaurus atherfieldensis by Norman (2012);[17] and made the holotype of a separate species Mantellodon carpenteri by Paul (2012),[18] but this is considered dubious and it is generally considered a specimen of Mantellisaurus[20] At the same time, tension began to build between Mantell and Richard Owen, an ambitious scientist with much better funding and society connections in the turbulent worlds of Reform Act-era British politics and science.

[22] With Benjamin Waterhouse Hawkins, he had nearly two dozen lifesize sculptures of various prehistoric animals built out of concrete sculpted over a steel and brick framework; two iguanodonts (based on the Maidstone specimen), one standing and one resting on its belly, were included.

[25][26][27] The largest find of Iguanodon remains to that date occurred on 28 February 1878 in a coal mine at Bernissart in Belgium, at a depth of 322 m (1,056 ft),[28] when two mineworkers, Jules Créteur and Alphonse Blanchard, accidentally hit on a skeleton that they initially took for petrified wood.

It was put together in a chapel at the Palace of Charles of Lorraine using a series of adjustable ropes attached to scaffolding so that a lifelike pose could be achieved during the mounting process.

When in the ground, the bones were isolated by anoxic moist clay that prevented this from happening, but when removed into the drier open air, the natural chemical conversion began to occur.

[37] During World War I, when the town was occupied by German forces, preparations were made to reopen the mine for palaeontology, and Otto Jaekel was sent from Berlin to supervise.

[48] In 2015 a new species of Iguanodon, I. galvensis, was named based on material including 13 juvenile (perinate) individuals found in the Camarillas Formation near Galve, Spain.

[29] These animals had large, tall but narrow skulls, with toothless beaks probably covered with keratin, and teeth like those of iguanas, as the name suggests, but much larger and more closely packed.

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

[60] With the advent of cladistic analyses, Iguanodontidae as traditionally construed was shown to be paraphyletic, and these animals are recognised to fall at different points in relation to hadrosaurs on a cladogram, instead of in a single distinct clade.

[101] Additionally, the front ends of the animal's jaws were toothless and tipped with bony nodes, both upper and lower,[29] providing a rough margin that was likely covered and lengthened by a keratinous material to form a cropping beak for biting off twigs and shoots.

The size of the larger species, such as I. bernissartensis, would have allowed them access to food from ground level to tree foliage at 4–5 metres (13–16 ft) high.

[11] A diet of horsetails, cycads, and conifers was suggested by David Norman,[28] although iguanodonts in general have been tied to the advance of angiosperm plants in the Cretaceous due to the dinosaurs' inferred low-browsing habits.

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.

[29] Large three-toed footprints are known in Early Cretaceous rocks of England, particularly Wealden beds on the Isle of Wight, and these trace fossils were originally difficult to interpret.

[110] 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.

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),[30] this does not necessarily mean these Iguanodon were herding animals.

[30] 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.

[28][41][63] A 2017 analysis showed that I. bernissartensis does exhibit a large level of individual variation in both its limbs (scapula, humerus, thumb claw, ilium, ischium, femur, tibia) and spinal column (axis, sacrum, tail vertebrae).

Additionally, this analysis found that individuals of I. bernissartensis generally seemed to fall into two categories based on whether their tail vertebrae bore a furrow on the bottom, and whether their thumb claws were large or small.

Two lifesize reconstructions of Mantellodon (considered Iguanodon at the time) built at the Crystal Palace in London in 1852 greatly contributed to the popularity of the genus.

In 1910 Heinrich Harder portrayed a group of Iguanodon in Tiere der Urwelt, a classic German collecting card game about extinct and prehistoric animals.

In the 2000 Disney animated film Dinosaur, an Iguanodon named Aladar served as the protagonist with three other iguanodonts as other main and minor characters are Neera, Kron and Bruton.

Its reconstructions have gone through three stages: the elephantine quadrupedal horn-snouted reptile satisfied the Victorians, then a bipedal but still fundamentally reptilian animal using its tail to prop itself up dominated the early 20th century, but was slowly overturned during the 1960s by its current, more agile and dynamic representation, able to shift from two legs to all fours.