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Dinosaur species


IguanodonIguanodon Iguanodon was a large ornithopod that lived during the Early Cretaceous Period. The ornithopods (the name means "bird feet", after their three-toed feet) were a group of ornithischians that developed the ability to chew their food. Iguanodon was capable of standing and walking on either two legs or four. Its long hindlegs had three toes and hoof-like nails, while the three middle fingers on its hands could be splayed wide to form a foot when on all fours. The other two digits on its five-fingered hands were a spiked thumb and flexible fifth finger for grasping. Iguanodon would have gathered its food using this flexible finger. It had a prominent snout and powerful, beak-like jaws for cropping off twigs and shoots.

Iguanodon skull, showing its cheek teethIguanodon skull, showing its cheek teeth


Iguanodon means “iguana tooth”: its tall cheek teeth resembled those of a modern iguana, a large lizard. Iguanodon’s teeth were positioned in its jaws in such a way that the upper teeth rubbed against the lower ones, grinding anything caught in between. Old worn teeth were replaced with new ones throughout its life. 

Thumb spike

Iguanodon using its thumb spike for defenceIguanodon using its thumb spike for defenceIf attacked by a large, hungry theropod and there was no chance of escape, a cornered Iguanodon had a lethal weapon it could rely on: its 15-centimetre (6-inch) thumb spikes. Rearing up on its hindlimbs, it would jab a spike into its attacker’s neck, eyes or belly. It was easily strong enough to penetrate the theropod’s thick hide.

Besides its most likely use as a defensive weapon, Iguanodon's thumb spike might also have come in handy for tearing down foliage or breaking into fruit.

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