Iguanodon is best known from Lower Cretaceous rocks of Bernissart, Belgium (where 31 adult skeletons were found in a coal mine at a depth of 321 meters). It is much larger and more specialized than CamptosaurusIguanodon had the following characteristics
- Had very long forelimbs (70 to 80% as long as hind limbs).
- The wrist bones were fused (for stable hand walking).
- Central 3 digits of the hand ended in hooves.
- Large conical thumb spike (perhaps a defensive weapon).
- Extensive boxwork of ossified tendons extending along the back vertebrae from the shoulder region to the middle of the tail.
Iguanodon probably did more quadrapedal walking than Camptosaurus or other small ornithopods. But could probably rear up on hind legs and swing its spike-like thumb for defense.
Description of Iguanodontids
- Iguanodontid snouts were long with many more teeth than in heterodontosaurids or hypsilophodontids.
- The beaks were used to crop vegetation.
- Teeth leaf-shaped with long ridges on their sides and small cusps on the cutting edges (resembling teeth of the living iguanas - thus the name for the family).
- Camptosaurus is the oldest iguanodontid and is best known from Upper Jurassic rocks of North America and Europe.
- The zenith of iguanodontid diversity occurred in Early to Medial Cretaceous time in Europe, North America, Africa, Asia, and Australia.
- Iguanodon, Lower Cretaceous of Europe, is the most typical representative of the Iguanodontidae and is the best known genus (with several complete skeletons known).
- A particularly unusual Lower Cretaceous iguanodontid is Ouranosaurus from Niger, Africa, which had a very distinctive head and long neural spines along the back (see page 212 in Fastovsky and Weishampel, 1996).
- There was a marked decline of iguanodontids in Late Cretaceous due (probably) to the appearance of the hadrosaurids (duck-bills).