Iguanodon bernissartensis

Iguanodon bernissartensis was a robust iguanodontian from the Barremian to earliest Aptian of western Europe. Its broad beak and tightly packed cheek teeth processed plants, while its unusually specialised five-fingered hands combined walking, grasping and a conical thumb spike. The Bernissart skeletons were historically mounted upright with their tails on the ground, but modern study places the trunk and tail much more horizontally and indicates that the animal could move on either two or four limbs.

Its fossils occur between approximately 126 and 122 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The skull ended in a toothless beak, with replacement teeth arranged behind it in grinding batteries. On each hand, the first digit formed the famous spike; the three central digits were bound into a hoof-like weight-bearing unit; and the mobile fifth digit could flex toward the palm. Powerful hind limbs, a broad pelvis and a tail stiffened by ossified tendons balanced the body. The palms faced inward rather than lying flat on the ground, so older reconstructions with splayed, pronated hands are anatomically misleading.

• Conical thumb spike formed by the first manual digit
• Three central fingers bound into a hoof-like support
• Mobile fifth finger capable of grasping toward the palm
• Broad keratin-covered beak for cropping vegetation
• Closely packed cheek teeth with continual replacement
• Powerful hind limbs and shorter weight-bearing forelimbs
• Deep tail stiffened by a lattice of ossified tendons

Coal miners encountered the great Bernissart bonebed 322 metres below ground in the Sainte-Barbe mine in 1878. Louis De Pauw directed the difficult recovery and preparation, while Louis Dollo studied and mounted the skeletons. George Albert Boulenger named Iguanodon bernissartensis in 1881. The genus Iguanodon itself had been coined by Gideon Mantell in 1825 from much more fragmentary English material; in 2000 the ICZN stabilised the name by making the Belgian species the genus's type species and designating IRSNB 1534 as its lectotype.

Discovery credit: Bernissart coal miners, Louis De Pauw.

Naming authors: George Albert Boulenger.

The Bernissart animals lived around a warm, humid freshwater wetland or swamp within a subsiding sinkhole system. The same deposit preserves fish, turtles, crocodile relatives, insects, conifers and abundant ferns, giving an unusually detailed view of the ecosystem. Exactly how the many iguanodons entered and accumulated in the bone-bearing clay remains debated, and the deposit may record more than one mortality event.

Iguanodon cropped vegetation with its beak and processed it with dental batteries. Limb proportions and hand construction support facultative locomotion: four-footed walking and feeding were possible, while the hind limbs remained dominant and bipedal movement was also available. The thumb spike could have served in defence, feeding or display, but no fossil records a strike. A concentration of many skeletons at Bernissart is compatible with social behaviour, yet a mass-death deposit alone cannot prove a permanent herd structure.

• The Brussels glass case displays eight original I. bernissartensis skeletons, while more can be seen in the positions in which they were found below the main gallery.
• The upright Brussels mounts are important historical artefacts, so their fragile originals were not remounted when scientific ideas about posture changed.
• Before the Bernissart hands were known, a thumb spike from fragmentary English fossils was famously mistaken for a nose horn.
• The first assembled Bernissart skeleton went on public display in 1883, only five years after the mine discovery.
• Pyrite within the bones caused severe conservation problems after excavation and helped drive more than a century of preservation work.

A research repository is not necessarily a public exhibit. Loan and display status can change, so check with the institution before visiting.

1. 01
   The Paleobiology Database

   Open source
2. 02
   On the ornithischian dinosaur Iguanodon bernissartensis from the Lower Cretaceous of Bernissart (Belgium)

   David B. Norman · Mémoires de l'Institut Royal des Sciences Naturelles de Belgique 178 · 1980

   Open source
3. 03
   Opinion 1947 Iguanodon Mantell, 1825: Iguanodon bernissartensis Boulenger in Beneden, 1881 designated as the type species, and a lectotype designated

   International Commission on Zoological Nomenclature · Bulletin of Zoological Nomenclature · 2000

   Open source
4. 04
   The Bernissart Iguanodons at a glance

   Institute of Natural Sciences, Brussels

   Open source
5. 05
   Le Musée de l'Iguanodon

   VisitWapi

   Open source
6. 06
   Iguanodon

   Muséum national d'Histoire naturelle

   Open source