|
|
|
|
 |
|
|
Hastings Iguanodon
 Hastings Iguanodon programme
Iguanodon bernissartensis
Resources
A dinosaur success story
One of the most successful and widespread of all dinosaurs, Iguanodon is a member of the plant-eating group called the ornithopoda. Primitive ornithopods were slim animals, about a metre long, that ran on their hind legs, but during the Late Jurassic and Cretaceous periods (see Timeline) giant, heavyweight ornithopods with bulky bodies evolved. These came to be one of the most important groups of dinosaurs and one of them, Iguanodon, is today one of the most studied and best understood of all dinosaurs.
First finds
Iguanodon fossils were first identified in the 1820s following discoveries made by Gideon Mantell, a medical doctor and palaeontologist from Lewes, Sussex. Mantell's fossils were just teeth and bone fragments, but following much discussion with the experts of the day he concluded that they represented a plant-eating lizard-like reptile more than 45 metres (150 feet) long. The true appearance of Iguanodon, however, was not revealed until 1878, when nearly 40 skeletons, many almost complete, were discovered 322 metres below ground in a coal mine in the Belgian town of Bernissart. These skeletons represented a species distinct from the material that had already been discovered in England, so in 1881 they were named as the new species Iguanodon bernissartensis.
Horny-beaked leaf eater
Iguanodon bernissartensis was a thick-set, robust dinosaur with a deep body. Several anatomical features would have made it look different from other large ornithopods. Its skull was proportionally large, its forelimbs were especially long and its tail was shorter than is usual for a big ornithopod. Like all ornithopods, it had a constantly-growing horny beak at the front of its mouth and would have used this to cut leaves, stems and twigs from plants. Leaf-shaped serrated teeth lined the margins of the jaws, and by slicing past one another as the jaws were opened and closed these would have chopped any plant material to tiny pieces.
Multi-functional hands
A surprising aspect of Iguanodon anatomy largely overlooked until the 1980s is that its hands were unique, multi-functional tools. The thumb was a conical spike, and it is tempting to imagine that it was used in fighting or self defence. The three middle fingers were stout, bound together at their bases; and the second and third were tipped with blunt hooves. In contrast, the fifth finger was quite flexible and could move independently of the others, so perhaps it was used to grasp vegetation.
Upright or all fours?
Though old pictures of Iguanodon show it standing upright like a kangaroo, various anatomical details show that nearly all dinosaurs walked with their backbones parallel to the ground. When I. bernissartensis was first reconstructed in this way, it turned out that its forelimbs were actually long enough to reach the ground. This probably explains the proportionally long forelimbs and stout, bound-together middle finger bones and finger hooves. We also now know of Iguanodon trackways, which show that these dinosaurs walked on all fours for at least part of the time. Some trackways also show several or many Iguanodons walking together, so they were probably herding animals.
Where iguanadon lived
We now know that, far from being restricted to Belgium, I. bernissartensis inhabited England, Germany, France, Spain, elsewhere in Europe and across Asia as far east as Mongolia. Some North American Iguanodon fossils may also show that I. bernissartensis successfully colonised this continent, though this remains controversial.
^ Top
|
|
|
