---
title: "Iguanodon bernissartensis:\nThe Dagger-Thumbed Colossus"
description: "Dalle origini del pianeta alle grandi estinzioni. Un viaggio attraverso 4 miliardi di anni di storia, dalle prime forme di vita dell'Adeano ai giganti del Mesozoico e oltre."
author: Angelo Denitto
url: https://noidinosauri.it/en/dinosaurs/ornithischians/ornithopods/iguanodon
---

![](https://noidinosauri.it/images/encyclopedia/dinosaurs/iguanodon/iguanodon-bernissartensis-early-cretaceous-river.webp)

![](https://noidinosauri.it/images/encyclopedia/dinosaurs/iguanodon/iguanodon-bernissartensis-early-cretaceous.webp)

### Reproduction

Like most ornithopod dinosaurs, *Iguanodon* was almost certainly **oviparous**, laying its eggs in terrestrial nests or large mounds built from rotting vegetation. While direct evidence of nesting remains rare, the highly gregarious behavior documented in fossil beds strongly suggests they used collective nesting grounds. Multiple adult females likely shared these large clearings, relying on the herd for community defense against egg-thieves and predators.



Hatchlings sported very different proportions than the adults, featuring significantly longer hind limbs relative to their forelimbs. This anatomical quirk indicates that juveniles were exclusively bipedal, capable of sprinting away from danger with a reactivity their adult bulk would eventually prevent. As they grew and their bulk steadily accumulated, their gait smoothly transitioned into the efficient bipedal-quadrupedal alternation seen in mature adults. Paleontologists also suspect a degree of **sexual dimorphism** existed within the herds, as certain skeletons appear noticeably more robust, though confidently telling males from females remains a tough challenge.

### The Extinction

The disappearance of *Iguanodon bernissartensis* didn't stem from a fiery cosmic catastrophe, but from a much quieter, relentless process: **ecological replacement**. Toward the end of the Early Cretaceous, the European ecosystem underwent massive paleogeographical shifts. The Laurasian archipelago fragmented, sea levels rose, and the rapid spread of the first flowering plants (**angiosperms**) radically transformed the available food web.



In this shifting landscape, more advanced ornithopods—the direct ancestors of the great **hadrosaurids** (duck-billed dinosaurs)—proved vastly more efficient at processing these new, tough plant types. They slowly but surely invaded the ecological niches that *Iguanodon* had dominated for millions of years. There was no sudden collapse; just a gradual erosion of a competitive edge. *Iguanodon* wasn't defeated by an asteroid, but by the very force that originally forged it: relentless evolution.

## Curiosity - Did you know?

### The Horn That Wasn't a Horn



For over fifty years after its discovery, scientists mistakenly glued the lethal thumb spur of *Iguanodon* right onto its nose, making it look like a massive, scaly rhinoceros.This enduring misunderstanding — almost comical in hindsight — stemmed from the very first fragmentary fossils found in England, where an isolated conical bone logically seemed to belong on the creature's snout. The spectacular 1878 Bernissart mine discoveries finally corrected the record. That pointed bone wasn't a facial ornament at all; it was a deadly weapon located on the wrist—a built-in dagger meant to tear flesh in desperate close-quarters combat.



### Dinner in the Belly of the Beast



*Iguanodon* sparked the world's very first dinosaur craze, long before Hollywood invented prehistoric blockbusters. In 1854, sculptor Benjamin Waterhouse Hawkins built imposing life-size concrete dinosaur models to inaugurate the Crystal Palace gardens in London. *Iguanodon*—still wildly inaccurate and sporting a nose-horn—was the star of the show. The night before the grand opening, Hawkins hosted a lavish gala dinner for twenty-one elite scientists entirely inside the hollow mold of the *Iguanodon*. They literally ate a banquet in the belly of the beast to celebrate the triumph of paleontology. You can still visit these protected historical sculptures in London today!

Was the Iguanodon bipedal or quadrupedal?

It was both. *Iguanodon* was a facultative biped. it walked on all fours to comfortably support its massive weight while grazing, but it could seamlessly rear up and run efficiently on its two powerful hind legs to flee predators or reach high vegetation.

What was the spike on the Iguanodon's hand used for?

The famous thumb spike was a lethal defensive weapon. Rigidly fused to the wrist, it had no grasping function. Instead, it worked like a natural brass knuckle or dagger, allowing the dinosaur to strike devastating blows against predators during close-quarters combat.

IMPORTANT - Some statements regarding behavior, coloration, and sensory abilities reflect ongoing scientific hypotheses, not established certainties.