Dinosaurs of The Isle of Wight - Ornithischians

Created Nov 29, 2001 | Updated Jul 26, 2013

The Ornithischian (bird-hipped) dinosaurs are one of the two major subdivisions of the Dinosauria, and consist of predominantly herbivorous dinosaurs.

Iguanodon

The first ornithiscian dinosaur, Iguanodon was discovered in Ringmer, East Sussex (UK) by Gideon Mantell¹. Since then several different species of Iguanodon have come to light. These include Iguanodon anglicum, Iguanodon ottingeri, Iguanodon mantelli, Iguanodon gracilis, Iguanodon lakotaensis, Iguanodon hoggi, Iguanodon dawsoni, Iguanodon fittoni, Iguanodon orientalis and Iguanodon seeleyi.

Two different species of Iguanodon have been found on the Island, Iguanodon atherfieldensis and Iguanodon bernissartensis. Iguanodon atherfieldensis is named after Atherfield Point on the Island, the location where the type specimen was found. The major differences between the two species are found in the structure of the skull, pelvis and feet.

Iguanodon Atherfieldensis

Iguanodon atherfieldensis, translated as Atherfield's Iguana-tooth, was first discovered by Reginald Hooley in 1917, and has since been discovered in Belgium, Spain, France and Germany. It grew to between six and seven metres long.

In comparison to other Iguanodons, Iguanodon atherfieldensis has a relatively low skull, forelimbs that are half the length of the hind limbs, and a short thumb spike. This type of Iguanodon was probably suited for low-level browsing and grazing.

Iguanodon bernissartensis

In 1878, nearly 40 skeletons of Iguanodons were found in a coal mine in Bernissart, Belgium, 26 of which were complete. Using these remains, Louis Dollo constructed Iguanodon as a kangaroo-like biped, a view that continued into the 1960s. He realised that Iguanodon's horned nose was an incorrect intepretation of a thumb spike.

Iguanodon bernissartensis, like atherfieldensis has been found on mainland Europe as well as the Island. Many complete skeletons are on display in the Institut Royal des Sciences Naturelles de Belgique.

Iguanodon bernissartensis was larger than Iguanodon atherfieldensis, growing to between 10 and 13 metres long. Its forelimbs are three quarters the size of its hind limbs. It had large, robust hands and an elongated thumb-spike.

Hypsilophodon foxii

Hypsilophodon foxii (meaning Fox's high-crowned tooth) was a small, fast biped.

The first specimen was discovered on the Island by William Buckland in 1832, yet both he and Sir Richard Owen considered it to be a juvenile Iguanodon. Reverend Fox noted several differences to Iguanodon, and considered it to be a new species - a view confirmed by Thomas Huxley, who named Hypsilophodon after him.

Hypsilophodons have only been found on the Isle of Wight. Palaeontologist Dr Dave Martill of Portsmouth University feels that as many as 5,000 Hypsilophodon specimens exist on the Island, all of which drowned when trapped in a tremendous flash flood. Until massive excavations take place, this can only be viewed as conjecture.

Most Hypsilophodon skeletons on the Island average around 1.5 metres in length, although it is believed that they grew as large as 2.3 metres. Although initially believed to have been able to climb trees and cliffs, it is more likely that Hypsilophodon was a ground-dwelling browsing omnivore, eating insects, small animals and vegetation, and capable of moving at speed. This is again conjecture, as no one faced with the skeleton of a goat would ever believe its arboreal capabilities

Valdosaurus canaliculatus

Valdo means Weald, and canaliculatus refers to the canal between the two condyles at the end of the femur. Valdosaurus has been discovered on the Isle of Wight, Sussex and Romania. Specimens are in the Natural History Museum and the Isle of Wight Museum of Geology.

Valdosaurus was around 1.5 metres tall at hip level, and 3.5 to 5 metres long. It was a herbivore, and like Iguanodon it could walk either quadrupedally or bipedally.

Yaverlandia bitholus

Yaverlandia bitholus is, so far, the only Pachycephalosaur to have been found on the Isle of Wight. Pachycephalosaurs were 'thick headed' dinosaurs who are believed to have used their thick, domed skulls as weapons. Yaverlandia is believed to have been one of the earliest, and most primitive pachycephalosaurs. Only one other Pachycephalosaur has been found in Europe, consisting of a tooth found in Portugal that has been named Taveirosaurus costai.

The species name of Yaverlandia bitholus, meaning twin-domed, is a reference to the skull's unique twin frontal bones. The only specimen discovered so far was a skull discovered in Yaverland, Isle of Wight. This find was 2 metres in length, but some believe it was a juvenile, and the adult would have reached greater proportions.

Stegosaur

A pubis discovered on the Isle of Wight has been identified as belonging to a stegosaur. Many scientists believe it could belong to Regnosaurus Northamptoni, the first stegosaur to be discovered (1838). This discovery initially caused much confusion as only a right mandible was recovered. It was at first believed to belong to Hylaeosaurus, although it was also believed to be from either an Iguanodon or a sauropod. Recently it has been confirmed as belonging to a stegosaur.

Other stegosaurs so far discovered include Kentrosaurus, Huayangosaurus, Craterosaurus and, of course, Stegosaurus, first discovered in 1877.

Some experts believe that the stegosaur was approximately 4 metres long, and would not only eat at ground level, but be able to rear up and eat higher vegetation.

Polacanthus foxii

Polacanthus foxii, ('Fox's many spined') was discovered by the Reverend Fox on the Isle of Wight in 1865. So far, three Polacanthus foxii specimens have been found, two on the Isle of Wight, and one in Dorset.

Other species of Polacanthus may have existed. Possibilities include Polacanthus rudgwickensis, found in Rudgwick, in Surrey, with other possible members of the Polacanthidae including the American Hoplitosaurus, and a newly-discovered specimen found in Spain. Specimens exist in the Natural History Museum, Sedgwick Museum in Cambridge and Blackgang Chine.

Polacanthus foxii was over 5 metres long, with a low, arched profile. Covered in spines, and an armoured shield, it was well protected. It was a herbivore, and probably ate close to the ground. A Polacanthus foxii can be seen in Walking With Dinosaurs: Giants Of The Skies, and on the BBC's Walking With Dinosaurs website.

Hylaeosaurus armatus

Hylaeosaurus, or 'forest-lizard', was the third dinosaur to be discovered and named (1833). Along with Iguanodon and Megalosaurus, it was one of the original three dinosaurs in the Dinosaurian pantheon. Hylaeosaurus, like Polacanthus, is an armoured ankylosaur, with large spikes and pointed armour plates. It was considered to be the same genus as Polacanthus, but recent study has shown that Hylaeosaurus does not have a co-ossified scapukocoroid, and there are also differences in the shape of the tibia and the arrangement of armour. Also unlike Polacanthus, it did not have a sacral shield of fused osteoderms.

Initial belief that Hylaeosaurus and Polacanthus were the same genus and species occurred largely because the first Polacanthus specimen consisted only of the hindparts, and the first Hylaeosaurus discovered consisted only of the foreparts.

Due to this confusion, Hylaeosaurus has been thought of as being discovered on the Isle of Wight, when in fact the Isle of Wight remains were those of Polacanthus. It is possible that a specimen is waiting to be found on the Island.

Hylaeosaurus was smaller than Polacanthus: approximately 4 metres long, with a similar diet.