Dinosaur discovery Iguanodon

Once you have found your fossil, it needs to be studied scientifically in order to reveal its identity, its relationship to other known organisms, as well as more detailed aspects of its appearance, biology, and ecology. To illustrate a few of the trials and tribulations inherent in any such programme of palaeontological investigation, we will examine a rather familiar and well-studied dinosaur: Iguanodon. This dinosaur has been chosen because it has an interesting and appropriate story to tell, and one with which I am familiar, because it proved to be the unexpected starting point for my career as a palaeontologist. Serendipity seems to have a o significant role to play in palaeontology, and this is certainly true 0 for my own work. |

The story of Iguanodon covers almost the entire history of scientific s research on dinosaurs and also the entire history of the science t now known as palaeontology. As a result, this animal unwittingly S illustrates the progress of scientific investigation on dinosaurs (and other areas of palaeontology) during the past 200 years. The story also reveals scientists as human beings, with passions and struggles, and the pervasive influence of pet theories at times in the history of the subject.

The first bonafide records of the fossil bones that were later to be named Iguanodon date back to 1809. They comprise, among indeterminable broken fragments of vertebrae, the lower end of a large, very distinctive tibia (shin bone) collected from a quarry at Cuckfield in Sussex (Figure 6). This particular fossil was collected by William Smith (often referred to as the 'father of English geology'). Smith was then researching the first geological map of Britain, which he completed in 1815. Although these fossil bones were clearly sufficiently interesting to have been collected and

Bone Tibia From Iguanodon

6. The first Iguanodon bone ever collected, by William Smith at Cuckfield in Sussex, in 1809

preserved (they are still in the collections of the Natural History Museum, London), no further study was made of them. The bones languished unrecognized until I was asked to establish their identity in the late 1970s.

Yet 1809 was a remarkably opportune moment for such a discovery to be made. Things were happening in Europe in the branch of science concerned with fossils and their meaning. One of the greatest and most influential scientists of this age, Georges Cuvier (1769-1832), was a 'naturalist' working in Paris and an administrator in the Emperor Napoleon's government. 'Naturalist' was, in these times, a broad category denoting the philosopher-scientist who worked on a wide range of subjects associated with the natural world: the Earth, its rocks and minerals, fossils, and all living organisms. In 1808, Cuvier redescribed a o renowned gigantic fossil reptile collected from a chalk quarry at 0 Maastricht in Holland; its renown stemmed from the fact that it | had been claimed as a trophy of war during the siege of Maastricht j in 1795 by Napoleon's army. The creature, originally mistaken for a 1 crocodile, was identified correctly by Cuvier as an enormous marine t lizard (later named Mosasaurus by the English cleric and naturalist S the Revd William D. Conybeare). The effect of this revelation - the existence of an unexpectedly gigantic fossil lizard of a former time in Earth history - was truly profound. It encouraged the search for, and discovery of, other giant extinct 'lizards'; it established, beyond reasonable doubt, that pre-biblical 'earlier worlds' had existed; and it also determined a particular way of viewing and interpreting such fossil creatures: as gigantic lizards.

Following the defeat of Napoleon and the restoration of peace between England and France, Cuvier was finally able to visit England in 1817-18 and meet scientists with similar interests. At Oxford he was shown some gigantic fossil bones in the collections of the geologist William Buckland; these seemed to belong to a gigantic, but this time land-living, lizard-like creature, and they reminded Cuvier of similar bones that had been found in

Normandy. William Buckland eventually named this creature Megalosaurus in 1824 (with a little help from Conybeare).

However, from the perspective of this particular story, the really important discoveries were not made until around 1821-2 and at the same quarries, around Whiteman's Green in Cuckfield, visited by William Smith some 13 years earlier. At this time, an energetic and ambitious medical doctor, Gideon Algernon Mantell (1790-1852), living in the town of Lewes, was dedicating all his spare time to completing a detailed report on the geological structure and fossils in his native Weald district (an area incorporating much of Surrey, Sussex, and part of Kent) in southern England. His work culminated in an impressively large, well-illustrated book that he published in 1822. Included in this book were clear descriptions of several unusual, large reptilian teeth and ribs that he had been unable to identify properly. Several of M these teeth were purchased by Mantell from quarrymen, while | others had been collected by his wife, Mary Ann. The next three £ years saw Mantell struggling to identify the type of animal to which these large fossil teeth might have belonged. Although not trained in comparative anatomy (the particular specialism of Cuvier), he developed contacts with many learned men in England in the hope of gaining some insight into the affinity of his fossils; he also sent some of his precious specimens to Cuvier in Paris for identification. At first, Mantell's discoveries were dismissed, even by Cuvier, as fragments of Recent animals (perhaps the incisor teeth of a rhinoceros, or those of large, coral-chewing, bony fish). Undeterred, Mantell continued to investigate his problem, and finally found a likely solution. In the collections of the Royal College of Surgeons in London he was shown the skeleton of an iguana, a herbivorous lizard that had recently been discovered in South America. The teeth were similar in general shape to those of his fossils and indicated to Mantell that they belonged to an extinct, herbivorous, giant relative of the living iguana. Mantell published a report on the new discovery in 1825 and the name chosen for this fossil creature was, perhaps not surprisingly, Iguanodon. The name means, quite

7. One of the original Iguanodon teeth found by the Mantells literally, 'iguana tooth' and was created yet again, at the suggestion of Conybeare (clearly the latter's classical training and turn of mind gave him a natural facility in the naming of many of these early discoveries).

Not surprisingly, given the comparisons then available, these early discoveries confirmed the existence of an ancient world inhabited by improbably large lizards. For example, a simple scaling of the minute teeth of the living (metre-long) iguana with those of Mantell's Iguanodon yielded a body length in excess of 25 metres. The excitement, and personal fame, engendered by the description of Iguanodon drove Mantell to greater efforts to discover more about this animal and the fossil inhabitants of the ancient Weald.

For several years after 1825, only fragments of Weald fossils were discovered; then, in 1834, a partial, disarticulated skeleton „ (Figure 8) was discovered at a quarry in Maidstone, Kent. | Eventually purchased for Mantell, and christened the £ 'Mantel-piece', it proved to be the inspiration behind much of his later work and resulted in some of the first visualizations of dinosaurs ever produced (Figure 9). He continued probing the anatomy and biology of Iguanodon in his later years, but much of this was, alas, overshadowed by the rise of an extremely able, well-connected, ambitious, and ruthless personal nemesis: Richard Owen (1804-1892) (see Figure 1).

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