The Changing Shape of a Dinosaur 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 asserted that Iguanodon was bipedal, based upon evidence of footprints and fossils found by Beckles. The early reconstructions by Owen of a quadruped were scoffed at by some as being curious relics of a bygone age.

This notion of bipedality was totally vindicated 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 Museum of Natural History in Brussels,   one of the best group displays of dinosaurs anywhere. 

Reconstruction of a Bernissart Iguanodon, supervised by Louis Dollo, in a church - the only building large enough for the operation

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.

Reconstructed skeleton of Iguanodon mantelli from Bernissart 1884, from the Royal Museum of Natural History in Brussels. (Also thought to be the first published illustration of an actual skeletal mount.)

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.

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.