Temporal range: Early Cretaceous
A restoration of Iguanodon bernissartensis by Gabriel Ugueto
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
clade: Dinosauria
Superorder: Ornithopodomorpha
Family: †Iguanodontidae
Genus: Iguanodon
Mantell, 1825
Type species
Iguanodon bernissartensis
Boulenger, 1881
Referred species
  • I. bernissartensis (Boulenger, 1881)
  • I. galvensis (Verdú et al., 2015)
  • I. ottingeri (Galton and Jensen, 1979)

Iguanodon is a genus of ornithopod dinosaur that lived from about 139-122 million years ago, from the early to late Cretaceous period. Iguanodon was the second dinosaur ever discovered and it was one of the first dinosaurs ever to be named, preceded only by Megalosaurus.

Iguanodon's name means "iguana tooth" due to its iguana-like teeth. It was the largest member of its family. It lived in Europe, mainly in the areas correlate to modern day England in the U.K. as well as in the areas correlating to modern areas of Belgium.

Discovery and history[]

The discovery of Iguanodon has long been accompanied by a popular legend. The story goes that Gideon Mantell's wife, Mary Ann, discovered the first teeth of an Iguanodon in the strata of Tilgate Forest in Whitemans Green, Cuckfield, Sussex, England, in 1822 while her husband was visiting a patient.


Iguanodontid distribution throughout the Earth

  • 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, although he had previously stated in 1827 that Mrs. Mantell had indeed found the first of the teeth later named Iguanodon. Other later authors agree that the story is not certainly false. It is known from his notebooks that Mantell first acquired large fossil bones from the quarry at Whitemans Green in 1820.[1][2]

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.[2]

However, assistant-curator Samuel Stutchbury recognised that they resembled those of an iguana he had recently prepared, albeit twenty times longer.

Mantell's "Iguanodon" restoration based on the Maidstone "Mantellodon" remains in recognition of the resemblance of the teeth to those of the iguana, Mantell decided to name his new animal Iguanodon or "iguana-tooth", from iguana and the Greek word ὀδών (odon, odontos or "tooth").

Based on isometric scaling, he estimated that the creature might have been up to 18 metres (59 feet) long, more than the 12-metre (39 ft) length of Megalosaurus.

His initial idea for a name was Iguana-saurus ("Iguana lizard"), but his friend William Daniel Conybeare suggested that that name was more applicable to the iguana itself, so a better name would be Iguanoids ("Iguana-like") or Iguanodon.

Mantell sent a letter detailing his discovery to the local Portsmouth Philosophical Society in December 1824, several weeks after settling on a name for the fossil creature. The letter was read to members of the Society at a meeting on 17 December, and a report was published in the Hampshire Telegraph the following Monday, 20 December, which announced the name, misspelled as "Iguanadon".


The first reconstruction of Iguanodon by Mantell

A more complete specimen of similar animal was discovered in a quarry in Maidstone, [3][4][5] Kent, in 1834 (lower Lower Greensand Formation), which Mantell soon acquired. The Maidstone slab was utilized 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. 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 in London. The borough of Maidstone commemorated this find by adding an Iguanodon as a supporter to their coat of arms in 1949.

  • Mantellisaurus-skull-full

    The skull infamously attributed and attached to classic Igianadon turned out to directly belong to Mantellisaurus

    It is classified as cf. Mantellisaurus by McDonald (2012); as cf. Mantellisaurus[6] atherfieldensis by Norman (2012); and made the holotype of a separate species Mantellodon carpenteri by Paul (2012), but this is considered dubious and it is generally considered a specimen of Mantellisaurus Statues in Crystal Palace Park[7] based on the Maidstone specimen of "Iguanodon", designed by Benjamin Waterhouse Hawkins, after restoration in 2002.

At the same time, tension began to build between Mantell and Richard Owen, an ambitious scientist with much better funding and society connections in the turbulent worlds of Reform Act-era British politics and science.

Owen, a firm creationist, opposed the early versions of evolutionary science ("transmutationism") 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 feet), determined that they were not simply giant lizards, and put forward that they had advanced and mammal-like, characteristics.[1]

In 1849, a few years before his death in 1852, Mantell realised that iguanodonts were not heavy, pachyderm-like animals, as Owen was putting forward, but had slender forelimbs; however, his passing left him unable to participate in the creation of the Crystal Palace dinosaur sculptures, and so Owen's vision of the dinosaurs became that seen by the public for decades.



Skeletal reconstruction of Iguanodon by randomdinos

Iguanodon were bulky herbivores that could shift from bipedality to quadrupedalism. The only well-supported species, I. bernissartensis, is estimated to have weighed about 5-6 tonnes, and measured about 10 metres (33 feet) long as an adult, with some specimens possibly as long as 11 metres (36 feet).

Model natural history museum londonscience

Iguanadon in a Bipedal gait/posture. Credit: natural history museum of london / london science

These animals had large, tall but narrow skulls, with toothless beaks probably covered with keratin, and teeth like those of iguanas, but much larger and more closely packed.

The arms of I. bernissartensis were long (up to 75% the length of the legs) and robust, with rather inflexible hands built so that the three central fingers could bear weight. The thumbs were conical spikes that stuck out away from the three main digits. In early restorations, the spike was placed on the animal's nose.

Iguanodon hand fossil natural history museum london

Iguanadon hand fossil; showing the infamous '' Spike '' . Credit: Natural History museum of London

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 was elongated and dextrous, and could have been used to manipulate objects.

PNSO Harvey The Iguanodon Scientific Art Model

Harvey; the iguanadon. Credit: PNSO

The phalangeal formula is 2-3-3-2-4, meaning that the innermost finger (phalange) has two bones, the next has three, etc. 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 tendons, which were tendons that turned to bone during life (these rod-like bones are usually omitted from skeletal mounts and drawings).

Modern Iguanadon artist unknown

Modern interpretation of Iguanadon. Credit: Unknown

Iguanadon jackwood thewoodparable 1280

Modern Iguanadon reconstruction with plumage ( its unknown if Iguanadontids had coverings like this ) Credit: jackwood @thewoodparable

Iguanodon teeth are, as the name suggests, like those of an iguana, but larger. Unlike hadrosaurids, which had columns of replacement teeth, Iguanodon only had one replacement tooth at a time for each position.

The upper jaw held up to 29 teeth per side, with none at the front of the jaw, and the lower jaw 25; 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-like structure, muscular or non-muscular, to retain food in the mouth. Quite similar to modern herbivores of today; such as Bovines and Cervids.

Classification and evolution[]

PNSO Harvey The Iguanodon Scientific Art Model 2

Harvey The Iguanodon Scientific & Accurate Model. Credit: PNSO

Iguanodon gives its name to the unranked clade Iguanodontia, a very populous, diverse and common group; with the moniker of worlds most successful dinosaurs for iguanodon itself; of ornithopods with several well known species known from the Middle Jurassic to the Late Cretaceous.

Aside from Iguanodon, the best-known members of the clade include Dryosaurus, Camptosaurus, Ouranosaurus, and the duck-bills, or hadrosaurs. In oldest sources, Iguanodontidae was shown as a distinct family. This family traditionally has been something of a wastebasket taxon.

In practice, animals like Callovosaurus, Camptosaurus, Craspedoeon, Kangnasaurus, Mochlodon, Muttaburrasaurus, Ouranosaurus, and Probactrosaurus were usually assigned to this family.


Iguanodontid classification by Norman 2015

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.

Iguanodon itself lies between Camptosaurus and Ouranosaurus in cladograms, and is probably descended from a camptosaur-like animal. At one point, Jack Horner suggested, based mostly on skull features, that hadrosaurids actually formed two more distantly related groups, with Iguanodon on the line to the flat-headed hadrosaurines, and Ouranosaurus on the line to the crested lambeosaurines, but his proposal has been rejected.



An Iguanodon Skeleton

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 (such as Megalosaurus) became, Iguanodon has had a complicated history, and its taxonomy continues to undergo revisions.


A pair of Iguanodons traveling on a coast. Credit: daniel eskridge

Although Gregory Paul recommended restricting I. bernissartensis to the famous sample from Bernissart, ornithopod workers like Norman and McDonald have disagreed with Paul's recommendations, except exercising caution when accepting records of Iguanodon from France and Spain as valid.


A pair of Iguanadons caught on a forest fire. Watching pterosaurs flying away. Credit: angie rodrigues

I. anglicus was the original type species, but the lectotype was based on a single tooth and only partial remains of the species have been recovered since. In March 2000, the International Commission on Zoological Nomenclature changed the type species to the much better known I. bernissartensis, with the new holotype being IRSNB 1534.

A herd of Iguanadon travel

A herd of Iguanadons traveling. Credit: unknown

The original Iguanodon tooth is held at Te Papa Tongarewa, the national museum of New Zealand in Wellington, 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.



Iguanodon in the woods by Josh Johnson

When the first Iguanodon skeleton was discovered it 1822, was believed to walk much like an iguana, on all four legs. Its thumb spike was believed to be a horn on its head (only one thumb spike was found). At one point it was also thought to have lived in trees, but this has been long since proven completely wrong.


A large herd of Iguanadons. Credit: corey ford

One of the more noticeable and clearly observable characteristics of the Iguanodon species is its "thumbs". Instead of a thumb it had a large spike that paleontologists believed Iguanodon individuals used for defensive purposes, and could also been used for getting food. The "pinky" finger of an Iguanodon is believed to have acted as its thumb.

Iguanodon-dinosaurs herd-elena-duvernay

A herd of Iguanadon drinking. Credit: elena duvernay / fineart america

Paleontologists believe and theorize that Iguanodon may have traveled in herds. In large herds of Iguanodons and other dinosaurs, mainly the ankylosaur family, would join in the migrations to gain protection to the herd as a whole, and also additionally providing an escort.

Iguanodon 2018 Mark Witton

Iguanodon infighting. Credit: Mark Witton

Iguanadon's anatomical gait generally thought as quadupedal, although it could have stood up on its hind legs as well. Its purpose for bipedal gait is generally to reach taller, harder to reach plants, as well as for a fast getaway and even stood on guard against potential predators such as Neovenator, Baryonyx, and other such theropods.

Iguanadon with hatchlings sciencephoto

An Iguanadon watching over the hatchlings. Credit: sciencephoto

They didn't have too flat of bills or like their hadrosaur descendants, but still had many teeth within its cheeked jaws and could chew tough food pretty easily. Thanks to this revolutionary adaptation, Iguanodon was perhaps the most successful dinosaur genus, with it and its relatives being found on nearly every continent across multiple eras.

Predation and Predators[]

Baryonyx feast

A Baryonyx feasting on a iguanadontid; quite likely subadult iguanadon carcass. Meanwhile a Neovenator standing closeby.

Its unclear if Iguanadon; at the very least fully mature specimens; had any significant natural predators given to their rather large size; bulky anatomy and natural defenses such as their infamous hand spike.


A Baryonyx harasses and challanges a trio of Iguanadontids. Credit: VectorStock

Meanwhile the adults could assumed to be far safer from the opportunistic predators such as Neovenator, Baryonyx, Larger species of Dromaeosauridae and similar theropods; the subadults as well as the juveniles; on the other hand; were in direct threat from all the aforementioned theropods. Presumably the elderly, ill, injured and disabled specimens were prone to danger as well.

Baryonyx iguanodon chase by ryn0saur d2

A Baryonyx chases and harasses a subadult iguandontid; presumably an iguanadon. Credit: ryn0saur

A direct evidence for the predation on Iguanadontids comes from the Spinosaurid Baryonychinae Baryonyx. The only known Specimen's cavity found with fish bones as well as digested remains belonging to a subadult iguanadontid. Its unknown if this represents a scavenging event or an occurance of direct predation.

Another noteworthy evidence comes from Iberian Baryonychinae Spinosaur Iberospinus, this theropod if found to be in direct association to several iguanadontid; likely Iguanadon specimens.

Its unknown if these specimens represent scavenging or actual predation; albeit given the number of occurances and the number of directly attributed iberian spinosaurid-iguanadontid fossils; the predation theory seem to be more probable; instead of a one-time scavenging event.

In popular culture[]

Iguanodon has been featured in several dinosaur-related merchandise ever since the early 1990s, reaching high popularity ever since the early 2000s.

  • An animated skeleton of Iguanodon was featured in one of the four episodes of the 1992 four part PBS documentary The Dinosaurs!. It was seen in the 1st episode "The Monsters Emerge.", where the skeleton of Iguanodon was changing its position and posture, and began to walk.
  • Iguanodont

    North American Iguanodon in Walking with Dinosaurs, reassigned to Dakotadon as of 2008

    Iguanodon first had its initial major appearance in the famous 1999 Walking with Dinosaurs documentary, and was shown to have travelled in herds with Polacanthus in North America (this Iguanodon species has since been assigned to the newer Dakotadon genus). European variants appear in England and are attacked by a pack of carnivorous Utahraptor, and one of them was killed in the process.
  • Iguanodon appear in various The Land Before Time films and TV series episodes, mostly as either minor or background characters, starting with 1995's The Land Before Time III: The Time of the Great Giving.
  • 1Dinosaur-Aladar

    Aladar from Disney's Dinosaur

    An Iguanodon named Aladar who was raised by lemurs was the main character in the 2000 Disney film, Dinosaur. This film was by far Iguanodon's most popular appearance to date. Aladar was attacked by a Carnotaurus and a pack of Velociraptor, before meeting a herd of Iguanodon and other animals trying to get to a nesting ground valley. Another Iguanodon in the movie was a female who later became Aladar's mate named Neera, her brother named Kron, and the anti-hero named Bruton and Aladdar's true mother.
220px-Iguanodon Crystal Palace

Outdated, Old Iguanodon Statues in Crystal Palace Park, now actually depictions of Mantellodon.

  • Iguanodon is one of the statues of dinosaurs in the Crystal Gardens in England.[7]
  • It appears in 2001's Jurassic Park III: Park Builder game.
  • Iguanodon was planned to appear in the 2003 game Jurassic Park Operation Genesis. For unknown reasons, the development of Iguanodon was terminated. The CD-ROM contains two files containing the parameters of the dinosaur.
  • It appears in Jurassic Park Builder where while it has cheeks, it lacks its classic thumb claw and the head shape is a bit off.
  • Iguanodon can be unlocked in Jurassic World Evolution, added in the Cretaceous Dinosaur Pack DLC released on December 13, 2018. Its appearance in the game is incredibly accurate (in fact it's one of the most accurate appearances in a video game yet), and is the only ornithopod in the game so far that is capable of defending itself against small and medium carnivores.
Jwd iguanodon

iguanodon in Jurassic World: Dominion

  • In Papua New Guinea, people have said a few remaining living Iguanodon-like dinosaurs are still alive today, but there is no evidence to confirm its existence.
  • Iguanodon is shown in Dinosaur King
  • Iguanodon made an appearance in the Roblox game Dinosaur Simulator.
    • Iguanodon is also playable in the Roblox game Prior Extinction.
  • Iguanodon is a playable in the game Path of Titans.
  • Iguanodon bernissartensis appears in Prehistoric Kingdom.

References about Iguanodon Predation[]

  • Credit Morphofunctional Analysis of the Quadrate

    A description of Spinosaurid diet; adds the Baryonychinae consumption of iguanadontids; on more than one occasion. Credit: Morphofunctional Analysis of the Quadrate of Spinosauridae

  • Credit weeklydinosaurs

    A paragraph explaining Baryonyx opportunistic and generalist dietary preferences as a Carnivore. Credit: weeklydinosaurs

  • Credits Kirkby Teaching Resources

    Another scientific paragraph explaining the generalistic and opportunistic carnivorous nature of Spinosaurids and Baryonychinae subfamily; by explaining the Stomach contents of The only known Baryonyx specimen; these contents include Iguanadon as well. Credits Kirkby Teaching Resources

    Credit Natural History Museum

    A paragraph explaining the stomach contents ( which includes subadult Iguanadon ) of the Baryonyx. Additionally explaining about Spinosaurids and Baryonychinae's generalist, opportunistic carnivorous behavior. Credit: Natural History Museum

Page References[]