Iguanodon

Early Cretaceous (130-125 million years ago)

Iguanodon holds a singular place in the history of palaeontology. It was one of the first dinosaurs ever formally described, named by Gideon Mantell in 1825 from teeth found in Sussex, but the Isle of Wight has produced some of the most important Iguanodon material in the world. The island's Wessex Formation has yielded numerous specimens ranging from isolated bones to near-complete skeletons, and the genus has become almost synonymous with the island's fossil heritage.

The animal was a large herbivorous dinosaur, reaching lengths of around ten metres and weighing perhaps four tonnes. It walked primarily on its hind legs but could drop to all fours when moving slowly or feeding. The most distinctive feature was the large conical thumb spike, which Mantell originally interpreted as a nose horn, an error that persisted for decades until more complete specimens revealed the true anatomy. The thumb spike was probably used in defence against predators or in feeding, perhaps to break open tough seed cases or strip bark from trees.

Isle of Wight Iguanodon material comes primarily from the Wessex Formation, a sequence of river and floodplain sediments laid down during the Early Cretaceous when the island sat in a subtropical latitude roughly equivalent to modern-day North Africa. The climate was warm and seasonal, with distinct wet and dry periods that are recorded in the alternating mudstones and sandstones of the formation. Iguanodon shared this environment with a diverse fauna including the carnivore Neovenator, the armoured Polacanthus, and numerous smaller dinosaurs, crocodilians, and turtles.

The taxonomy of Iguanodon has been revised repeatedly over the past two centuries. At various times, dozens of species were assigned to the genus, many of them based on fragmentary material from across Europe. Modern revisions have pruned this considerably, and most Isle of Wight material is now referred to Mantellisaurus atherfieldensis or retained in Iguanodon bernissartensis, depending on the size and detailed anatomy of the specimen. The distinction matters because it reflects genuine biological diversity rather than mere variation within a single species.

Museums across the island and the mainland hold important Iguanodon specimens from the Isle of Wight. The Dinosaur Isle museum at Sandown, before its closure, displayed several significant finds, and the Natural History Museum in London holds type specimens collected from the island's coast in the 19th and early 20th centuries. New material continues to emerge from the eroding cliffs, particularly after winter storms strip away fresh exposures of the Wessex Formation.

The cultural impact of Iguanodon extends well beyond palaeontology. The Crystal Palace Iguanodon sculptures of 1854, though anatomically inaccurate by modern standards, were among the first life-sized reconstructions of any dinosaur and helped to establish the animals in the public imagination. The Isle of Wight's continuing association with the genus has made it a pilgrimage site for dinosaur enthusiasts from around the world.