The thumb spike that was once a nose horn
Iguanodon—"iguana-tooth"—was named in 1825 by Gideon Mantell and became the second dinosaur formally named from fossils, after Megalosaurus. Today's genus centres on I. bernissartensis from Early Cretaceous western Europe, about 126 to 122 million years ago: bulky herbivores nine to eleven metres long and roughly 4.5 metric tons.
Distinctive anatomy includes large thumb spikes likely used in defence, plus long grasping fifth fingers for foraging. Mantell based the name on English teeth that matched iguanas scaled up roughly twentyfold, after Samuel Stutchbury spotted the resemblance at the Royal College of Surgeons. Early estimates pushed length toward eighteen metres; Friedrich Holl supplied the species name anglicum (later anglicus) in 1829. With Megalosaurus and Hylaeosaurus, Iguanodon helped define Dinosauria.
A popular tale credits Mantell's wife Mary Ann with finding the first teeth in Sussex in 1822, but notebooks show Mantell collecting large bones at Whitemans Green by 1820, and he later admitted finding the teeth himself. Experts first dismissed them as fish or rhinoceros; Georges Cuvier briefly agreed, then affirmed they were reptilian and possibly from a giant herbivore after Buckland's Megalosaurus description. The 1834 Maidstone slab guided early art—yet Mantell perched a supposed nasal horn that later proved to be the thumb spike.
Belgian mine finds of 1878, studied by Louis Dollo, yielded I. bernissartensis. Twenty-first-century revision split English "Iguanodon" material into Mantellisaurus, Barilium, and Hypselospinus; I. anglicus is a nomen dubium, so the name sticks to the Belgian-centred species, with I. galvensis added from Iberia in 2015. Owen's heavy Crystal Palace beasts, including a banquet held inside a standing sculpture, shaped public dinosaurs for decades even after Mantell realised the forelimbs were comparatively slender.
Source: Iguanodon
