The Bernissart Iguanodons

The eight Iguanodon bernissartensis specimens shown in the glass case vary greatly in size: they range from 629 to 730cm long and 390 to 506cm high! The sole Mantellisaurus atherfieldensis (former Iguanodon mantelli or Iguanodon atherfieldensis) specimen is much smaller: 391cm long and 362cm high.

Pyrite may shine like gold, but it is nothing more than iron sulphide (FeS2) and it is worthless. Hence its nickname, ‘Fool’s Gold’.

The Bernissart iguanodon skeletons were completely filled with pyrite. When clay from the swamps covered the dinosaur corpses, they were decomposed by blue-green algae (cyanobacteria). The acid released reacted with the iron in the clay, thus forming pyrite. It gradually filled the many holes in the bones.

The word ‘pyrite’ is derived from the ancient Greek puritês lithos, meaning ‘fire stone’.

Prehistoric men would use it to make fire, by striking pyrite against flint until there were sparks. The sparks caused a dry tinder fungus to glow, which set fire to dry twigs and grass.

The Cran of the Iguanodons: this was the name of the clay-filled pit containing the skeletons.

Several galleries 322m deep were dug. At the entrance to the main one, two iguanodons were discovered in a vertical position with their skulls downwards.
The other skeletons, more in the centre, were more or less horizontal.

As they were released they were divided into blocks. These – a total of almost 600! – were coated with plaster and taken to the surface in horse-drawn trucks.

During the excavations, the skeletons were divided into blocks of 0.5 – 2m (the contours are visible in this drawing). Each specimen received a letter and each block a number, and their exact positions were recorded.

Once the fossils were moved to the Museum workshops, it was possible to carefully return them to their original positions.

This depiction of an Iguanodon bernissartensis was drawn by Gustave Lavalette in 1883.

This specimen is a lot smaller than the others.

Its skeleton differs slightly from that of the Iguanodon bernissartensis, but to be certain that they belong to separate species we would have to let them mate (if they can reproduce and their offspring is not sterile, they belong to the same species).
This is obviously out of question with creatures that have been dead for millions of years! So the mystery has not been solved.

In 1882, under the direction of Louis Dollo, Louis De Pauw (the man with the beard, bended on one knee) began assembling the most complete specimens in their “probable life posture”.

Due to their size, a room with a high ceiling was required. They used the St George chapel (today part of the Royal Library). Here, they built a scaffold hung with ropes.

The best position for each bone was obtained by adjusting the length of the ropes. Finally, once the skeletons would be assembled, they would be fitted with an iron frame to hold the bones in place.

In the 1880s, the Nassau Hotel had become too small to exhibit the iguanodons.

The "Museum" was thus transferred to a building in the Park Leopold: the “Convent”, to which they added the Janlet wing, which is where the iguanodons were kept from 1902 onwards.

This photo was taken during its construction in 1900, right about where today’s glass case begins.

The iguanodons have been in the Janlet wing since 1902 but they were exposed to the air until 1932!

Due to the temperature and moisture variations, they slowly but surely began to crumble. This is why all the skeletons were dismantled between 1933 and 1937 and soaked in a protective mixture of alcohol and shellac.
Their brown colour is therefore not the result of being found in a coal mine.

The iguanodon skeletons were dismantled once again in 1940: it was feared they might be damaged or even completely destroyed during the bombings.

They were kept in cellars whose openings were protected by sandbags. But those were so damp that the iguanodons had to be returned to the room before the end of the Second World War!

They may have been assembled and dismantled several times but the iguanodons are still standing in the same biped kangaroo position they were put in during the first assembly.

The Bernissart fish lived in fresh water.

This Amiopsis dolloi resembles the contemporary Amia calva, a swamp fish found in the Everglades, in Florida (USA).

Chitracephalus (on right) protected its head by folding its neck sideways and Peltochelys (on left) by retracting it vertically.

These turtles resemble contemporary species living in fresh water.

This tiny crocodile was discovered for the first time in Bernissart, hence its name: Bernissartia fagesii. Its back was covered with several rows of plates. The specimen on display is barely 66cm long.

Goniopholis simus, the largest of the Bernissart crocodiles, was almost two metres long.

Unlike the Bernissartia fagesii, it had only two rows of dorsal plates.

This cone (Pityostrobus bernissartensis) and this piece of glazed wood (Pinoxylon) are conifer fossils, also discovered in Bernissart.

Most of the fossil plants from Bernissart are from buckler ferns, Weichselia reticulata.
The herbivorous iguanodons probably ate a lot of them.

Bernissart was a hot, swampy region: several of its fossilized specimens lived only in hot climates (crocodiles, cicada etc.) and swamps (fish Amiopsis, ferns Weichselia etc.).