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[ig gwah' no don] "iguana tooth"; one of the first dinosaurs ever described


The largest Iguanodon was about 30 feet long, 16 feet high (9 feet at hips), and weighed about 3 tons.

Like most ornithopods, Iguanodon was an occasional biped: this dinosaur spent most of its time grazing on all fours, but was capable of running on its two hind legs (at least for short distances) when it was being pursued by predators.

The most outstanding feature of Iguanodon was a highly specialised, five-fingered hand made up of an erect and spiked thumb, three webbed middle fingers, and a grasping fifth finger. Iguanodon was also the first dinosaur to develop back teeth for grinding food, and it was also capable of moving its lower jaw back and forth.


Herds of Iguanodon flourished in Europe, North Africa, Asia, and, probably, North America during the Cretaceous Period (135-100 million years ago).


Iguandon's strong teeth suggest that it ate tough plants. It probably ate standing on all fours, and used its bony beak to nip off plants, such as palms and ferns. Some scientists have also suggested that the Iguanadon might have had a long tongue, like a giraffe.


Like other dinosaurs, Iguanodon probably laid eggs.


Since dozens of fossils have been found together at a few sites, Iguanodon was most likely a herd animal.

Fossil History

The first Iguanodon fossils ever found were some teeth and bones discovered in Sussex, England, in 1822. Their discoverer, Gideon Mantell, thought the bones resembled modern-day iguanas, and it was he who coined the name Iguanondon, in 1825. One of the first dinosaurs ever described, it was the second to be given a name, after Megalosaurus. Several fossil footprints have also been found, with the greatest concentration being in the British Isles.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Archosauria
order Ornithischia
family Iguanodonidae
genus and species
Iguanodon anglicus
I. atherfieldensis
I. bernissartensis
I. dawsoni
I. fittoni
I. hoggi
I. lakotaensis
I. ootingeri

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The Robinson Library >> Science >> Geology >> Paleontology

This page was last updated on 05/18/2017.