Iguanodon is a genus of extinct ornithopod dinosaur that lived around 135 and 125 million years ago. It was one of the three genera, along with Megalosaurus and Hylaeosaurus, used to describe clade Dinosauria. The scientific understanding of this genus has evolved over the years. The taxonomy still stays a great topic for discussions as new dinosaur specimens are assigned to this genus. Scientists have recovered several ‘almost complete’ fossil samples from two bonebeds, paving the way for better understanding of the genus. Iguanodon was initially not a part of the dinosaur renaissance that started in 1969, but it soon grabbed everyone’s attention.

Physical Characteristics/Anatomy

It had a long and narrow skull with a toothless beak. However, their cheek was packed with closely bundled teeth that were similar to those of the Iguanas, but a bit larger. They had long and robust but inflexible hands. It had four fingers on their forelegs along with a conical spike. At first it was believed that the spikes were present on the animals’ nose, but later researchers suggested that they were near their foreleg fingers. Forelimbs were smaller than hind limbs. Each foot had three toes. Their legs were legs, but they were not made for running.

Adaptation and Behavior

Iguanodon was primarily thought to be a quadruped creature. Despite the lack of evidence, some large three-toed footprints, found in Europe, are often assigned to Iguanodon suggesting a quadruped adaptation. However, bipedal movement theory also circles around in the world of paleontology. It has also been suggested that they used their tail as a third leg to form a tripod while feeding. David Norman denied this theory suggesting that this posture was impossible with their stiffened tail.

It is believed that they lived in herds as evidenced by the discovery of the bonebed in Belgium. But some recent studies suggested that this theory may not be true. Scientists have also not found any evidence of sexual dimorphism.

One of their interesting features was their thumb spike. It was described as a dagger-like weapon to deal with predators. Some paleontologists also suggested that it could also have been used for plucking seeds or fruits.

Their eating habits are not well known. Iguanodon possessed the teeth of an herbivorous reptile, but there are several hypotheses as how it ate. English geologist and paleontologist Gideon Mantell suggested that it had a prehensile tongue like a giraffe. However, later analysis showed that this was not the case. It was stated that Iguanodon had a muscular, non-prehensile tongue. They probably had a cheek-like structure to retain food in their mouth. English paleontologist David Norman suggested a diet consisting of conifers, horsetails and cycads.

Discovery and Species

In 1822, few bones and teeth were found in Sussex, England. The genus was first described by English geologist Gideon Mantell in 1825. Mantell was the first to notice the similarity between the teeth of Iguanodon and modern-day Iguana. Hundreds of Iguanodon skeleton and bone remains have been found from several parts of the world, like the United States, northern Africa and Europe (Belgium, England, and Germany). Iguanodon remains (I. orientalis) have also been found in Mongolia. In 1881, Boulenger and van Beneden named the type species I. bernissartensis. In 1834, a more complete specimen was unearthed in the lower Lower Greensand Formation in Maidstone, Kent. The specimen is currently on display at the Natural History Museum in London. The largest specimen was accidentally found by two mineworkers, in 1878, in a coal mine at Bernissart in Belgium. At first, they thought it to be a petrified wood. Several specimens have been assigned to this genus. The history of this genus is a bit complicated, and it continues to go through revisions. I. bernissartensis is the neotype for this genus. This species is primarily known from the Bernissart sample, but several other samples have also been found throughout Europe.

Etymology

The name “Iguanodon” comes from the words Iguana, a genus of herbivorous lizards, and the Greek word ‘odous’ meaning tooth. The name is thus because the teeth of Iguanodon were similar to those of the Iguanas. At first, Mantell thought of giving the name Iguanasaurus (meaning “Iguana lizard”), but William Daniel Conybeare suggested that Iguanodon or Iguanoides (meaning “Iguana-like”) would be more appropriate.

Interesting Facts

• Iguanodon has featured in several documentary films, movies and TV series, such as Disney film Dinosaur, BBC’s Walking with Dinosaurs, Dinosaur Planet and Raptor Red among others.
• 1989 CB3, a main belt asteroid, has been given the name 9941 Iguanodon.
• Dinosaur genus Mantellisaurus was earlier known as Iguanodon atherfieldensis. While, genus Therosaurus species T. anglicus was earlier known as Iguanodon anglicus.
• Along with Tyrannosaurus and Stegosaurus, Iguanodon was one of the dinosaur genera to have inspired the appearance of Godzilla.