This page is the second on the Dinosaur section of our website to undergo change, please bear with us while these alterations take place. We aim to provide a lot more information than was previously published on the website, and to make the information available at a range of levels to suit many interests. This may take a while but we hope that you will like the results as they appear.

Iguanodon (pronounced 'Ig-wan-oh-don') was one of the first dinosaurs to be discovered.  The name is derived from 'Iguana' - a type of modern reptile, and 'don' meaning tooth.

Iguanodon is the name of a small group of dinosaurs within the much larger group called Iguanodontids; they were large herbivores, with a long tail for balance, and hind legs that were longer than their fore limbs.  There were three large hooved toes on each foot, and four fingers and a thumb spike on each hand.  The mouth had a battery of chewing teeth, and a boney beak in place of front teeth.  Since its initial discovery in the early nineteenth century, and more detailed reconstructions after complete skeletons were found in a Belgian mine in 1878, we have been forced to re-evaluate its posture, shape and movement; and to look again at how it fits in with other members of the Iguanodontids. Fossil remains from the group show they existed from the late Jurassic through to the late Cretaceous.

Here on the Isle of Wight it was once thought there were two basic species of Iguanodon; a larger form called Iguanodon bernissartensis, and a more graceful species called Iguanodon atherfieldensis.  The first was named after the Belgian town where complete skeletons were found (Bernissart) and the latter from Atherfield on the south west coast of the Isle of Wight.  However more recently palaeontologist Gregory Paul has moved our smaller variety to a new genera, leaving us with only one Iguanodon but a new genera of Iguanodontid called Mantellisaurus atherfieldensis (named after Gideon Mantell) in its place. It was initially very difficult to identify, name and group these animals from the fragmentary information that was first available in the Victorian era. As a result a number of names have now been discarded, some of which may appear in the 'Discovery' box below.

Systematic palaeontology
Dinosauria  Owen, 1842
Ornithischia  Seeley, 1888
Ornithopoda  Marsh, 1881
Iguanodontia  Dollo, 1888
Dryomorpha  Sereno, 1986
Ankylopollexia  Sereno, 1986
Iguanodontidae  Cope, 1869
Iguanodon  Mantell, 1825
Iguanodon bernissartensis  Boulenger, in Beneden, 1881

Research
It would not be possible to list every research paper that has ever been produced on the Iguanodontids so the selection below will hopefully provide an introduction. Iguanodon is still being researched; many bones have been found and as more are discovered it has become obvious that there is considerable variation even amongst Island fossils.  In addition to this variation there is also the historical problem generated due to the early definition of  the group. Some dinosaur remains that have been described as 'Iguanodon' are now being suggested as belonging to other dinosaurs, perhaps even new ones. At the moment the most significant change for our Island dinosaurs is the move of Iguanodon atherfieldensis to a new genera called Mantellisaurus atherfieldensis, first proposed by American palaeontologist Gregory Paul in 2006. The following year he published a proposed change (in Cretaceous Research) to the inter-relationship of a number of Iguanodonts, which then also included M. atherfieldensis.


References
Buckland, W. 1829. On the discovery of the bones of the Iguanodon and other large reptiles in the Isle of Wight and Isle of Purbeck. Proceedings of the Geological Society of London. 1. 159-160.

Martill, D.M. & Naish, D. 2001. Dinosaurs of the Isle of Wight. Field Guides to Fossils: Number 10. Palaeontological Association. p119-132.

Norman, D.B. 1980. On the ornithischian dinosaur Iguanodon bernissartensis from the Lower Cretaceous of Bernissart (Belgium). Memoires de l'Insitut Royal des Sciences Naturelles de Belgique, 178, 105pp.

Paul, G. 2006. Turning the old into the new: a separate genus for the gracile iguanodont from the Wealden of England. In: Carpenter, K. (Ed.), Horns and Beaks: Ceratopsian and Ornithopod  Dinosaurs. Indiana University Press, Bloomington, pp. 69-77.

Paul, G.S. 2007. A revised taxonomy of the iguanodont dinosaur genera and species. Cretaceous Research. doi 10.1016/j.cretres.2007.04.009

Size
Iguanodon bernissartensis typically grew to a length of 9 to 10 metres, however some much larger bones have been found which Martill and Naish (2001) suggest meant that specimens may have reached upto 13 metres long. Heights may have reached 3.5 to 4 metres tall.

The smaller Iguanodon atherfieldensis (now renamed Mantellisaurus atherfieldensis) grew to about 6 to 7 metres long.

Weight
To be updated.


Eats
Tough plants.

How fast could it run?
To be updated.


The geology and age
Lower Cretaceous
Wealden Group
Wessex Formation

Iguanodon remains are found throughout the the Wessex Formation rocks on the Island, which range from approximately 122 to 126 million years old; however some rare Iguanodon material is found in the younger lagoonal and estuarine rocks of the Vectis Formation, from about 122 to 120 Million years ago. Exceptionally rare bones have been found in the offshore sands of the Ferruginous Sands, presumably after their bodies had floated out to sea from land lying to the north. Since these sands range in age from about 116 to 113 million years ago it demonstrates the long period of time in which these plant-eating dinosaurs were roaming the local area.

Where was it found?
To be updated.

When was it first found?
To be updated.

Something different or unusual?
As a member of the Ankylopollexia it had fused bones in the wrists and a sharp thumb spike. Although this was once proposed as a defence mechanism against other dinosaurs some researchers now believe it may have had very little impact on a carnivorous dinosaur of the same size.

I. bernissartensis is now believed to have been bipedal, walking for most of the time only on its hind feet.  The evidence of the preserved footprints and footcasts shows that most of them are tridactyl (three-toed); and there are very few hand prints from this larger species.

With a higher shoulder than M. atherfieldensis and sharp serated teeth adapted to chopping harder vegetation it is thought this meant that fully grown I. bernissartensis adults browsed about 4 metres high. M. atherfieldensis had lower shoulders and appears to have walked on all fours for most of the time, suggesting it ate plants that were closer to the ground. Both species had teeth that were constantly growing and being replaced, suggesting a hard diet (with some dinosaurs of the type replacing teeth in less than a year). Iguanodonts had cheeks that enabled them to hold plant material in their mouths so that they could chew it up.

Many of the preserved footcasts are found near former river channels indicating that they may have congregated here for drinking in herds, or that they were using river banks as natural paths. Fossils from the group of dinosaurs called Iguanodontia have been found on all of the continents except for Antarctica (and that may only be because there is very little rock exposed there in which to find remains). Parallel trackways with footcasts of various sizes suggest they travelled in large mixed herds, most likely for defence. Like other ornithopods (meaning 'bird feet') they became more prolific at the time of the appearance of the first flowering plants.