Iguanodon

Iguanodon bernissartensis was a large ornithopod dinosaur that roamed Early Cretaceous Europe between 126 and 122 million years ago. This bulky herbivore measured up to 11 meters long and weighed around 4.5 metric tons, making it one of the largest plant-eaters of its time and place. It could walk on either two or four legs, likely dropping to all fours while grazing and rising onto its powerful hind limbs to reach higher vegetation or flee predators.

The most distinctive features of Iguanodon were its remarkable hands. Each thumb bore a large conical spike, likely used for defense against predators or possibly in combat with rivals. In contrast, its fifth finger was elongated and prehensile, capable of grasping vegetation much like a thumb works in reverse. The three middle fingers were robust and hoof-like, perfect for weight-bearing during quadrupedal locomotion.

Iguanodon holds a special place in paleontological history as only the second dinosaur ever to be scientifically named, following Megalosaurus. English physician Gideon Mantell described it in 1825 based on teeth discovered in Sussex. However, our modern understanding comes primarily from the spectacular 1878 discovery at Bernissart, Belgium, where miners struck a mass grave containing at least 38 individuals preserved in remarkable detail.

Early reconstructions famously placed the thumb spike on Iguanodon's nose like a rhinoceros horn—a mistake not corrected until the complete Bernissart specimens revealed the true anatomy. This error serves as a humbling reminder of how fragmentary fossils can mislead even brilliant scientists, and why complete specimens are so valuable to paleontology.