The Bernissart Iguanodons
Discoveries of new dinosaur genera in the US by Marsh and Cope revealed the distinct possibility that dinosaurs could have been bipedal - walked on two hind legs. Huxley had also believed that Iguanodon was bipedal, based upon evidence of footprints and fossils found by Beckles.
The early reconstructions by Owen of a quadruped were now scoffed at by some as being curious relics of a bygone age.
Reconstructed skeleton of Iguanodon mantelli from Bernissart 1884, from the Royal Belgian Institute of Natural Sciences in Brussels
Photograph of Iguanodon mantelli cast acquired by the British Museum of Natural History in 1895
The Reptile volume of Richard Lydekker's Royal Natural History contains a rarely-reproduced life restoration of the Iguanodon drawn by Alice B. Woodward in an upright position, derived from the recently installed specimen in the Natural History Museum
Louis Dollo's work
The belief that Iguanodon walked on two legs was further strengthened in 1878 when a whole herd of Iguanodon were found buried 321m deep in a coalmine at Bernissart, Belgium. It seems that 31 fully grown adults had fallen down a deep ravine during Cretaceous times, and had drowned as it filled with flood water and mud.
The fossils were slowly excavated under the supervision of Louis Dollo, who produced papers based on the finds and reconstructed the creatures skeletons. The first published restoration appeared in 1882.
Two different species were found - the smaller I. mantelli (well known from the English Weald), and a new larger species - I. bernissartiensis.
The skeletons were reconstructed in a church - the only building large enough to carry out the work - in an upright bipedal posture. They are now mounted in the Royal Belgian Institute of Natural Sciences in Brussels, one of the best group displays of dinosaurs anywhere.
And the issue of the horn?
It was evident from these specimens that Iguanodon had powerful hind legs, allowing it to stand upright, and keep it's arms free for grasping food. And the spike on it's nose was proved to be a large thumb spike, probably used for defensive purposes.
The reconstructed creatures
In 1895 the British Museum of Natural History acquired a cast of a Bernissart Iguanodon. Dollo's pose determined how Iguanodons were to be exhibited for nearly a century.