Reconstructing iguanodon

In 1878 remarkable discoveries were made at a coal mine in the small village of Bernissart in Belgium. The colliers, who were mining a coal seam over 300 metres beneath the surface, suddenly struck a seam of shale (soft, laminated clay) and began to find what appeared to be large pieces of fossil wood; these were eagerly collected because they seemed to be filled with gold! On closer inspection, the wood turned out to be fossil bone, and the gold 'fool's gold' (iron pyrites). A few fossil teeth were also discovered among the bones, and these were identified as similar to those described as belonging to Iguanodon by Mantell many years before. The miners had accidentally discovered not gold, but a veritable treasure trove of complete dinosaur skeletons.

Over the next five years, a team of miners and scientists from the 0 Royal Belgian Museum of Natural History in Brussels (now the |

Louis Dollo
11. Louis Dollo (1857-1931)

Royal Institute of Natural Sciences) excavated nearly 40 skeletons of the dinosaur Iguanodon, as well as a huge number of other animals and plants whose remains were preserved in the same shales. Many of the dinosaur skeletons were complete and fully articulated; they represented the most spectacular discovery that had been made anywhere in the world at the time. It was the good fortune of a young scientist in Brussels, Louis Dollo (1857-1931), to be able to study and describe these extraordinary riches, and this he did from 1882 until his retirement in the 1920s.

The complete dinosaur skeletons unearthed in Bernissart proved finally that Owen's model of dinosaurs such as Iguanodon was incorrect. As Mantell had suspected, the front limbs were not as large and strong as the back legs, while the animal had a massive tail (see Figure 12), and the overall proportions of a giant kangaroo.

M The skeletal restoration, and the process by which it was arrived at, ii are particularly revealing because they show how the influence of

12. Drawing of an Iguanodon skeleton the contemporary interpretations about the appearance and affinities of dinosaurs affected Dollo's work. Owen's 'elephantine reptile' vision of the dinosaur had been questioned as early as 1859 by some tantalizingly incomplete dinosaur discoveries made in New Jersey and studied by Joseph Leidy, a man of equivalent scientific stature to Owen who was based at the Philadelphia Academy of Natural Sciences. However, Owen was to be far more roundly criticized by a younger, London-based, and ambitious rival: Thomas Henry Huxley (1825-95).

By the late 1860s, a series of new discoveries had been made that added considerably to the debate over the relationships of dinosaurs to other animals. The earliest well-preserved fossil bird (called Archaeopteryx, or 'ancient wing') had been discovered in Germany (Figure 13). It was eventually bought from its private collector o by the Natural History Museum in London, and described by 0

Richard Owen in 1863. The specimen was unusual in that it had | well-preserved impressions of feathers, the key identifier for any j bird, forming a halo in the matrix around its skeleton; however, 1 unlike any living bird, and rather disconcertingly similar to modern t reptiles, it also had three long fingers ending in sharp claws on each S hand, teeth in its jaws, and a long bony tail (some living birds might seem to have long tails, but this is just the profile of their feathers that are anchored in a short remnant of the tail).

Not long after the discovery of Archaeopteryx, another small, well-preserved skeleton was found in the same quarries in Germany (Figure 14). It bore no feather impressions and its arms were far too short to have served as wings in any case; anatomically, it was clearly a small, predatory dinosaur and was named Compsognathus ('pretty jaw').

These two discoveries emerged at a particularly sensitive time scientifically speaking. In 1859, just a year or so before the first skeleton of Archaeopteryx was unearthed, Charles Darwin published a book entitled On the Origin of Species. This book

13. A well preservedArchaeopteryx specimen, discovered in 1876 (approx 40 cm long)

provided a very detailed discussion of the evidence in favour of the ideas being put forward by the transmutationists and progressionists referred to earlier. Most importantly, Darwin suggested a mechanism - natural selection - by which such transmutations might occur and how new species appear on Earth. The book was sensational at the time because it offered a direct challenge to the almost universally accepted authority of biblical teachings by suggesting that God did not directly create all the

14. Compsognathus skeleton (approx 70 cm long)

species known in the world. Darwin's ideas were vigorously opposed by pious establishment figures such as Richard Owen. In contrast, the radical intellectuals reacted very positively to Darwin's ideas. Thomas Huxley is reputed to have declared, after reading Darwin's book, 'How very stupid of me not to have thought of that!'

While not wishing to become too involved in Darwinian matters, it is nevertheless the case that dinosaurian discoveries featured in some of the arguments. Huxley was quick to realize that Archaeopteryx and the small predatory dinosaur Compsognathus were anatomically very similar. By the early 1870s, Huxley was proposing that birds and dinosaurs were not only anatomically similar, but used this evidence to support the theory that birds had evolved from dinosaurs. In many ways, the stage was set for the discoveries in Belgium. By the late 1870s, Louis Dollo, as a bright young student, would have been fully aware of the Owen-Huxley/ Darwin feuds. One burning question must have been: did these new discoveries have any bearing on the great scientific controversy of the day?

Careful anatomical study of the full skeleton of Iguanodon revealed that it had a hip structure known as ornithischian ('bird-hipped'); M furthermore, it had long back legs that ended in massive, but | decidedly bird-like, three-toed feet (very similar in shape to the feet £ of some of the biggest known land-living birds such as emus). This dinosaur also had a rather bird-like curved neck, and the tips of its upper and lower jaws were toothless and covered by, yet again, a bird-like horny beak or bill. Given the task of description and interpretation faced by Dollo in the immediate aftermath of these exciting discoveries, it is intriguing to note that, in the early photographs taken at the time of the reconstruction of the first skeleton in Brussels, just beside the huge dinosaur skeleton can be seen skeletons of two Australian creatures: a wallaby (a small variety of kangaroo) and a large, flightless bird known as a cassowary.

The influence of the debate raging in England cannot be doubted. This new discovery pointed to the truth implicit in Huxley's arguments and made it clear that Mantell had been on the right track in 1851. Iguanodon was no lumbering, scaly rhinoceros lookalike as portrayed by Owen in his grand models of 1854; rather it was a huge creature with a pose similar to that of a resting

15. Iguanodon being reconstructed at the Museum of Natural History, Brussels, in 1878. Note the cassowary and wallaby skeletons used for comparison.

kangaroo, but with a number of bird-like attributes, just as Huxley's theory predicted.

Dollo proved to be tirelessly inventive in his approach to the fossil creatures that he described - he dissected crocodiles and birds in order to better understand the biology and detailed musculature of these animals and how it could be used to identify the soft tissues of his dinosaurs. In many respects, he was adopting a decidedly forensic approach to understanding those mysterious fossils. Dollo was regarded as the architect of a new style of palaeontology that became known as palaeobiology. Dollo demonstrated that palaeontology should be expanded to investigate the biology, and by implication ecology and behaviour, of these extinct creatures. His final contribution to the Iguanodon story was a paper he published in 1923 to honour the centenary of Mantell's original discoveries. He succinctly summarized his views on the dinosaur, identifying it M as the dinosaurian ecological equivalent of the giraffe (or indeed | Mantell's giant ground sloth). Dollo concluded that its posture £ enabled it to reach high into trees to gather its fodder, which it was able to draw into its mouth by using a long, muscular tongue; the sharp beak was used to nip off tough stems, while the characteristic teeth served to pulp the food before it was swallowed. So firmly was this authoritative interpretation adopted, based as it was on a set of complete articulated skeletons, that it stood, literally and metaphorically, unchallenged for the next 60 years. This was reinforced by the distribution of replica, mounted skeletons of Iguanodon from Brussels to many of the great museums around the world during the early years of the 20th century, and also by the many popular and influential textbooks written on the subject.

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  • fastolph
    How dinosaur skeleton are reconstructed?
    8 years ago
    What is used to reconstruct a dinosaur skeleton?
    8 years ago

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