An Ultimate Guide to Iguanodon: The Iguana Tooth

Leave a comment / / Updated on: 20th September 2023

Name Meaning“The Iguana Tooth”Height3 meters (10 feet)
PronunciationIh-gwa-no-donLength9-11 meters (30-36 feet)
EraMesozoicEarly CretaceousWeight3.08-4.5 metric tons (6,790-9,921 pounds)
ClassificationDinosauria,‭ Ornithischia & OrnithopodaLocationEurope

Iguanodon Pictures

Iguanodon dinosaur walking in the desert by day
Iguanodon dinosaur walking in the desert by day | Elenarts108 via iStock

The Iguanodon

Gage Beasley Prehistoric's Iguanodon Concept
Gage Beasley Prehistoric’s Iguanodon Concept

If you’re a dinosaur enthusiast, you probably already know about or at least heard of the Iguanodon.

After all, it was one of the first discovered and named dinosaurs!

Besides this, the Iguanodon is known from so many specimens that scientists described more than ten species, but not all are recognized today.

This herbivorous dinosaur lived in Europe about 126-122 million years ago, and it was a large, bulky creature that could walk quadrupedally and bipedally.

Gage Beasley's Prehistoric Shirt Collection
Gage Beasley’s Prehistoric Shirt Collection

The Iguanodon had a distinctive thumb spike that likely helped it eat and defend itself from predators.

Moreover, its fifth finger was unusually long, being of excellent help in foraging.

This article contains some fascinating, well-detailed facts about the Iguanodon, and if you find this extinct creature interesting, keep reading!

Physical Characteristics

Like some other herbivores, the Iguanodon could walk on both four and two legs.

It had a bulky body, a relatively long neck, and a long tail.

Also, its skull was tall but narrow and featured a distinctive beak covered in keratin.

Gage Beasley Prehistoric's Iguanodon Concept
Gage Beasley Prehistoric’s Iguanodon Concept

The Iguanodon had 58 teeth on the upper jaw and 50 on the lower jaw.

The arms were long, representing about 75% of the hindlimb length, and quite robust.

The three central fingers on the forelimbs supported the dinosaur’s weight, with the little finger elongated and the thumb bearing a conical spike that might have been used as a foraging or defense aid.

On the other hand, the hind limbs had only three toes and were strong but not adapted for fast running.

The Iguanodon weighed roughly 9 meters (30 feet) long, although some might have grown much longer, reaching 13 meters (43 feet).

However, not all scientists support this maximum estimation, as some argue that there’s no way they reached more than 11 meters (36 feet) in length.

Either way, they were still giants, weren’t they?

Although the maximum weight is still debatable, some suggest a body mass of approximately 3.08 metric tons (3.40 short tons), while others argue in favor of 4.5 metric tons (5 short tons).

These numbers do not coincide if the calculations are done for different specimens, so having a precise average length and weight is quite challenging.

3D illustration of Iguanodon in a white background
3D illustration of Iguanodon in a white background | Warpaintcobra via iStock

After all, these creatures are known from more than 30 fossilized individuals!

As for the height, the Iguanodon probably stood around 3 meters (10 feet) tall at the hips.

If you’re acquainted with the T-Rex, you’ve probably already noticed that the Iguanodon resembles the ferocious carnivore in size, but that’s not something unusual for the members of the Iguanodontidae family.

Take Lurdusaurus, for example. Its tail only measured 4 meters (13 feet) long, and the total body length is estimated at 9 meters (30 feet).

Still, no member surpassed Iguanodon’s size!

Habitat and Distribution

Iguanodon fossils were discovered in the following localities:

  • Tilgate Forest, Sussex, England
  • Sainte-Barbe Clays Formation, Bernissart, Belgium
  • Wessex Formation, Isle of Wight
  • Nehden, Nordrhein-Westphalen, Germany
  • The upper Barremian Paris Basin deposits, Auxerre, Burgundy
  • Camarillas Formation, Galve, Spain

As you can observe, Iguanodon individuals were widely spread across Europe and quite abundantly, considering that only Belgium revealed more than 30 specimens.

However, we can assume that their distribution was distinctly limited within the continent’s northern and western parts. 

Studies show that the northwestern territory of Europe had a humid climate during the Late Jurassic and Early Cretaceous, which contrasted with arid periods.

Supposedly, there were seasonal shifts between humid and arid seasons.

Iguanodon was a herbivorous dinosaur that lived in Europe during the Cretaceous Period
Iguanodon was a herbivorous dinosaur that lived in Europe during the Cretaceous Period | CoreyFord via iStock

At least some territories, like the Camarillas Formation, had a marine influence and featured fluvial, lacustrine, and deltaic environments.

The Sainte-Barbe Clays Formation of Bernissart was likely a lacustrine environment as well, with hilly regions covered in vegetation like ferns, angiosperms, and freshwater algae.

The Wessex Formation of the Isle of Wight is considered to have been a semi-arid environment featuring conifer trees adapted to arid conditions.

The trees are considered more common near water sources, and xerophytic ferns likely served as ground cover.

Behavior and Diet

As already stated, the Iguanodon was both quadrupedal and bipedal.

When it walked on all four limbs, it held its palms facing each other and likely walked only on the fingers and toes.

Iguanodon dinosaur roaring while walking among ferns, cycas and wollemia plants by day with clouds
Iguanodon dinosaur roaring while walking among ferns, cycas and wollemia plants by day with clouds | Elenarts108 via iStock

Also, when moving quadrupedally, this dinosaur could only walk slowly.

Moving bipedally, however, it reached approximately 24 km/h (15 mph).

By far, the most distinctive characteristic of the Iguanodon is its thumb spike, which was originally thought to have belonged to its nose.

It used this stiletto-like spike as a weapon against predators and might have also aided in breaking fruits and seeds.

The fact that many specimens were discovered in the same localities (Benissart, for instance) may indicate that Iguanodon dinosaurs engaged in herding behaviors, but not all scientists accept this theory.

They argue that the lack of juvenile remains indicates that herding behavior was unpopular among Iguanodon populations.

Iguanodon herbivorous dinosaurs lived during the Cretaceous Period of Europe and walked with a herd of animals
Iguanodon herbivorous dinosaurs lived during the Cretaceous Period of Europe and walked with a herd of animals | CoreyFord via iStock

Luckily, fossils carry enough evidence indicating that these creatures were herbivores. 

Still, their feeding behavior, meaning how exactly they ate and ingested food and what they ate, is poorly known.

It has been previously thought that they also had a prehensile tongue used to gather food, but subsequent remains showed this was not the case.

Considering the skull structure, scientists concluded that the Iguanodon could likely chew its food, thus being capable of eating tough plants.

The cropping beak may have been used to bite off shoots and twigs.

It has also been suggested that these creatures went for plants as tall as 4-5 meters (13-16 feet) and ate cycads, conifers, and horsetails, although this hasn’t been fully confirmed yet. 

Life Cycle

Iguanodon dinosaurs herd walking at the shoreline
Iguanodon dinosaurs herd walking at the shoreline | Elenarts108 via iStock

Iguanodon dinosaurs reproduced by laying eggs.

Since females had two functional oviducts (unlike birds, which have only one), they laid two eggs at a time.

However, very little else is known about their reproductive behavior.

For example, the type of nests they built is unknown, and whether the parents cared for their newly hatched babies.

We may suppose that baby Iguanodon were precocial (meaning they didn’t require parental care after hatching, as they were quite developed already), as were many other dinosaurs, but this would only be a guess.

Additionally, since few juvenile fossils were discovered in association with adult specimens, this might indicate that parental care likely wasn’t common among these creatures.

Iguanodon dinosaur in dynamic posture
Iguanodon dinosaur in dynamic posture | leonello via iStock

As juveniles, Iguanodon dinosaurs were believed to have been primarily bipedal because their forelimbs were shorter than those of adults.

As they grew older and heavier, so did their forelimbs, and they gradually switched to a predominantly quadrupedal lifestyle.

At a time, Iguanodon individuals were thought to have been sexually dimorphic.

Supposedly, the females were smaller than the males, but this theory was disapproved shortly.

Evolution and History

The discovery of Iguanodon goes back to the early 1800s, and there’s a very interesting legend about it.

In 1822, Gideon Mantell, a British obstetrician, and paleontologist, and his wife, Mary Ann, were visiting his patient in Whitemans Green, Cuckfield, Sussex, England.

Skeletal reconstruction of Iguanodon
Skeletal reconstruction of Iguanodon | Slate Weasel via Wikimedia Commons

Supposedly, on their way to the patient, Mary Ann spotted something odd glinting by the side of the road.

She then discovered these were teeth embedded in rocks and informed her husband about them, who rushed to study them and determine what kind of teeth they were.

This story was often questioned, especially regarding who exactly found the teeth – was it Mary Ann, or was it, in fact, her husband?

Either way, the teeth were found; that goes without saying.

Gideon Mantell asked Georges Cuvier to study them, and at first sight, Cuvier thought the teeth belonged to a fish species similar to Teraodon (pufferfish).

However, the internal structure of the teeth indicated it might have belonged to a herbivorous reptile.

This theory remained implausible, as no herbivorous reptile had been discovered until then.

Iguanodon Teeth displayed in Natural History Museum
Iguanodon Teeth displayed in Natural History Museum | Joyofmuseums via Wikimedia Commons Creative Commons Attribution-Share Alike 4.0

Only later, Samuel Stutchbury, an English naturalist and geologist, realized that the teeth were similar to those of iguanas, except that they were much larger.

That’s how the name Iguanodon appeared.

Over the years, many discovered fossils have been attributed to Iguanodon, but not all are fully confirmed, while others have been reassigned to other genera.

Take the 1834 discovery from Maidstone, Kent. At first, Mantell identified the specimen as an Iguanodon, but it was later moved to Mantellisaurus.

These discoveries opened the doors toward a complete description of the Iguanodon and revealed fossils that made many things clear – for example, the location of the spike.

The most significant discoveries occurred in 1878 in Bernissart, Belgium, when at least 38 Iguanodon individuals were recovered.

Four years later, one of these specimens became the holotype specimen for Iguanodon bernissartensis and one of the first displayed dinosaur skeletons.

Iguanodon skull revealing the unique anatomy of this herbivorous dinosaur
Iguanodon skull revealing the unique anatomy of this herbivorous dinosaur | Ballista via Wikimedia Commons Creative Commons Attribution-Share Alike 3.0

The discovery of Iguanodon was also an excellent incentive for the development of fossil conservation, which wasn’t as well-developed then.

In the 20th century, 15 other dinosaur individuals were recovered from Germany, and some were attributed to Iguanodon bernissartensis.

Another species in the genus, Iguanodon galvensis, was named in 2015 upon discovering numerous individuals, including 13 juvenile dinosaurs, from Spain’s Camarillas Formation.

That’s how the Iguanodon came to be known as one of the first dinosaurs to be named and described.

However, things weren’t always as clear as today – a genus with three species.

Even though the taxonomy is still being revised, it is in a much better place today.

At least 16 species have been historically assigned to Iguanodon and then moved to different genera.

Iguanodon is believed to have been a large, bipedal dinosaur with a beak-like snout and teeth suited for grinding plant material
Iguanodon is believed to have been a large, bipedal dinosaur with a beak-like snout and teeth suited for grinding plant material | leonello via iStock

The other four species were first classified under some genera, then reassigned to Iguanodon, but none are recognized today.

In short, nothing is easy when it comes to the Iguanodon!

After all, it is one of the first-named dinosaurs, and it deserves a bit of mystery.

Interactions with Other Species

Since Iguanodon had a wide distribution across the territory we now call Europe, these creatures likely crossed paths with hundreds, if not thousands, of other prehistoric creatures.

Here are some of the creatures that Iguanodon might have crossed paths with:

  • Anteophthalmosuchus, a goniopholidid mesoeucrocodylian
  • Bernissartia, a neosuchian crocodyliform
  • Mantellisaurus, another iguanodontian dinosaur
  • Hyaleobatrachus, a salamander
  • Various theropods like Calamosaurus, Eotyrannus, Neovenator, Riparovenator, and Vectiraptor
  • Various titanosaurians
  • Ornithischias like Hypsilophodon, Valdosaurus, Vectipelta, and Polacanthus
  • Other saurischians like Chondrosteosaurus, Eucamerotus, Iuticosaurus, and Aristosuchus
  • Various fish species
  • Arthropods
  • Squamates
  • Turtles
  • Plesiosaurs
  • Mammals
  • Birds

Since it was quite a large herbivore, the Iguanodon likely had a major ecological role in its habitat.

Iguanodon dinosaurs make their way among the trees of a Cretaceous forest as reptiles species fly over
Iguanodon dinosaurs make their way among the trees of a Cretaceous forest as reptiles species fly over | CoreyFord via iStock

However, because many other creatures were herbivores, there was probably a bit of competition for food.

Although it shared its habitat with carnivorous theropods, many were much smaller than the Iguanodon, and it is unknown whether they preyed upon this giant herbivore.

On the other hand, it is well-known that many small theropods were ferocious predators that could hunt and kill large sauropods, so we cannot rule out this possibility.

Moreover, since its thumb spike is considered to have served as a defense mechanism, there must have been predators to fend off.

Cultural Significance

Since the Iguanodon is now probably one of the most popular dinosaurs worldwide, it’s no wonder it has a vast connection to popular culture.

Even back in the 1800s, two lifesize reconstructions were set for display!

Chromolithograph picture of iguanodon after a drawing by F. John
Chromolithograph picture of iguanodon after a drawing by F. John | ZU_09 via iStock

The Iguanodon has also been repeatedly portrayed in the media, so if you want to see it in motion, check out the following:

  • Dinosaur (Disney animated film)
  • The Land Before Time (films and TV series)
  • Walking with Dinosaurs (documentary mini-series)
  • The Lost World (book)
  • Raptor Red (book)
  • Jurassic Park: Dominion (film)
  • ARK: Survival Evolved (video game)
  • There’s even an asteroid called 9941 Iguanodon!


Having lived on Earth 126-122 million years ago, the Iguanodon is now the most renowned dinosaur genera.

The fossils belonging to this genus shed light not only on the appearance, behavior, and evolution of its members but on other dinosaurs as well.

They play a crucial role in understanding our world’s prehistoric wildlife and evolutionary history.

A large herbivore, this creature had the privilege of walking on both four and two legs.

It was widely distributed across Europe and shared its habitat with a myriad of other fascinating prehistoric creatures.

Because it is one of the first-named dinosaurs, the Iguanodon is now also a popular appearance in the media, which is undoubtedly great news for dinosaur enthusiasts!


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