Prehistoric Animals


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The Iguanodon was the "founding father" of dinosaurs, not in the sense of a common ancestor, but rather in that of their scientific understanding. In 1825, the Iguanodon became the second dinosaur to be named and was one of the three animals that allowed English paleontologist Sir Richard Owen to define the concept of "Dinosauria" in 1842. Since then, studies and reconstructions of Iguanodon have played a very big role in advancing our knowledge about dinosaurs. The Iguanodon inhabited a very extensive area during the lower Cretaceous: Europe, North America and Mongolia. The first fossil discoveries of this dinosaur were made at Wealden Rocks in southern England, rocks that formed in a succession of shallow lakes and estuaries. The earliest vestiges were teeth resembling those of an iguana, hence its name. As bones came to light, researchers gradually reconstituted this dinosaur as a large herbivorous quadruped, a kind of reptilian rhinoceros. But, they placed on the tip of the Iguanodon's nose a large bony horn found with other parts of the skeleton, which has become the most famous mistake in the history of paleontology. This first reenactment helped to reinforce the impression that dinosaurs were heavy animals. A perception that we know today wrong. And it took the most remarkable fossil of all time to actually bury that stereotype. In 1878, workers at a coal mine in southern Belgium dug up a big bone full of what they thought was gold.

Gold became that of the "cursed" (or pyrite), but the possibility of a treasure made them dig even more and led to the discovery of dinosaur skeletons. After three years, the complete skeletons of 31 Iguanodons were found and at that time were the best preserved dinosaur fossils. Studies of these specimens have shown that, far from being a heavy quadruped, the Iguanodon was relatively light for its immense length and could stand on its hind legs. These skeletons also showed the location of the famous bone tip. In fact, there were two, one on every thumb. Nearly a century after these events, the Iguanodon and other large ornithopods, such as hadrosaurids, have been reconstituted rather like huge kangaroos, standing on their hind legs, head up and tail stretching out along the ground. And it was not until the 1970s that new studies revealed that the Iguanodon had powerful forelimbs and that its three central fingers ended in hooves. This implied that the Iguanodon sometimes walked on all fours, but probably stood on its hind legs to move quickly and run. As in ornithopods, its backbone was supported by large ossified tendons around the pelvis, but arranged in the form of trellises, rather than parallel as in other species of the same genus. The jaw and teeth of Iguanodon made it an effective herbivore. In addition, a large number of narrow and filled teeth were very well suited for spraying hard plants, the upper surface of each tooth being wide and striated. The jawbones that held the teeth moved up and out as the animal chewed, allowing the grinding teeth to rub against each other and contribute to the effectiveness of this action. The same arrangement has been observed in a large number of other ornithopods.