Iguanodon (Iguanodon ottingeri)

Iguanodon was a very successful species of large herbivores whose remains have been found all over the world

Size

Iguanodon ottingeri grew to lengths of up to 10 meters.

Behaviour

Generalised Iguanodon behaviour:

  • Most (but not all) Iguanodon species were facultative bipeds, meaning that they were capable of walking on two legs, but spent most of their time on four. Evidence suggests that young Iguanodon may have been more adapted for walking on two legs than adults.
  • Iguanodon's fingers were specialised for defence, notably its thumbs, which featured a prominent spike. When Iguanodon was first discovered, the thumb spike was originally placed on the animal's nose.
  • Iguanodon's estimated maximum running speed was 24km/hr, which could only be achieved by running upright: Iguanodon's spine was very inflexible vertically, so it would have found galloping on all fours very difficult.
  • In Europe, Iguanodon fossils are often found in groups of 3 or 4 individuals rather than herds. However, fossilized Iguanodon tracks, and a trove of 37 individual fossils at the Bernissart site, seem to suggest that at least some Iguanodon species lived in herds.
  • Able to chew to a degree.

Position in Food Chain

Herbivorous, likely to be browse on low-level plants and trees.

Habitat

Iguanodon ottingeri is found in the same Cedar Mountain formation as Gastonia, suggesting it lived on an arid floodplain.

Reconstruction

Reconstructing Iguanodon ottingeri may be a problem, as it is currently known only from teeth. New fossils found in the Dalton Wells Quarry have been diagnosed as Iguanodon ottingeri, but they have not yet been fully described. They are said to be similar to Iguanodon lakotaensis in some respects and may have been sail-backed, so we can use this dinosaur as a basis for our reconstruction.

Recreating Iguanodon for Earthsim

Color

It is likely the sail was used primarily for display, and was probably more colourful than the rest of the body.

Sounds

These are large herbivores, hence in Earthsim we have decided to use a combination of heavy bleating or honking sounds.

Visual Reconstruction

SPECIES 1. Iguanodon ottingeri

Iguanodon ottingeri is currently known only from teeth and is considered a nomen dubium, or a species that is dubious and invalid. However, new specimens of sail-backed iguanodontids from the Dalton Wells Quarry (which have not been described), have been diagnosed as I. ‘ottingeri’. They are said to be similar to I. lakotaensis in some respects and may have been sail-backed too. Unless these specimens are described soon, the species ottingeri will not be considered further, and this document concentrates on I. lakotaensis.

SPECIES 2. Iguanodon lakotaensis

Only the skull is known. However, work by Norman has shown it is maybe the same as Iguanodon bernissartensis, a very common European species known from many complete skeletons. Our restoration of I. lakotaensis will therefore rely heavily on I bernissartensis, as a guide. The only difference will be the presence of a sail on the back.

General dimensions

Up to 10m long. The forelimbs would be 50-70% the length of the hindlimbs – shorter in younger individuals. There are at least three different reconstructions of the skeleton of this animal in side view. Young Iguanodon may have had different posture to adults (see below).

Skull

In general appearance, the iguanodontid skull is “vaguely reminiscent of those of horses”. The rear of the skull (all that behind the orbits) is box-like, with rather straight edges. As such, the rear of the skull is almost a perfect square when seen from the front/back, and an elongate rectangle shape from above/below. The parts of the skull in front of the orbits, do not conform to this simple box design – they taper gradually forward, and expand outwards at the tip: the tip of the jaws are formed by a continuously growing beak, the outer edge of which is almost flat and horizontal when seen from the front, and broadly rounded when seen from above. The beak edge is slightly crenulated in the fossil material, but this would have been overlain by horny keratin material in life, and the edge would have been sharp and smooth in life. Moving back along the skull from the beak, the snout is narrower and the skull only widens out again at the level of the eyes and beyond. This gives the skull as a whole a ‘waisted’ appearance from above. The jaw line is almost straight for most of its length, running from just past the orbit, forward to the rear of the beak. However the line shifts downwards here, and the line of the beak is displaced considerably lower relative to the rest of the jaw line. The jaw articulation is also very much lower than the jaw line. This gives the jaw line a slightly arch-like contour when seen from the side. This slightly arched outline also occurs on the lower margin of the jaws, and the upper margin of the skull in side view. Where the upper and lower jaws meet, there is a very slight overbite. The chin juts out slightly. The orbits are round and positioned high on the skull, facing outwards and slightly forwards. A bone over-lying the orbit forms a slight ‘brow’. The top of the head is rather flat. The teeth are inset (fig 2E), indicating the presence of a soft cheek…

Teeth

The teeth are leaf-shaped and reminiscent of those of iguanas (hence the name Iguanodon, don=tooth). The outer margin is crenulated.

Skull: facial features (fig 3)

With no horns or projections, Iguanodon is probably the most ‘featureless’ dinosaur in the ecosystem. A cheek would have covered the sides of the face up to the beak. The tongue would have been muscular and probably long, to help process and masticate food. The eyes were on the sides of the head.

Legs and posture

In a normal resting pose, Iguanodon would have had all four limbs on the ground. The fore limbs were about 60% of the length of the hind limbs. The knee was at roughly the same level as the shoulder, and the backbone tapered slightly downwards towards the neck. The tail was held above the ground. In younger individuals, the legs were proportionately longer, and juveniles may have walked on two feet, only moving to four feet in older age.

Hands

The 5-fingered hands of Iguanodon are very distinctive. Digit one is a thumb spike (see below). The middle three fingers would have been used for supporting the weight, and 2 and 3 bear blunt ‘hooves’. The fifth or ‘little’ digit is smaller and more flexible and points outwards. The angle between digit 1 and 5 is about 90 degrees. Each finger would have appeared distinct in life, but the three middle fingers were joined for much of their length. In a neutral standing position, the hands would have been oriented palm to palm, with the thumb spikes projecting forwards.

Hind feet

Each of the three toes on the hind feet of Iguanodon bear ‘hoof’-like claws. The middle toe pointed forwards and the outer toes splayed outwards to about 40 degrees to the middle toe. Iguanodon footprints are very common, and indicate that a padded heel formed the rear or the foot. This can be seen in the gallery images.

The ‘torso’

The body is deep and rounded. It will appear especially deep from the side because of the raised sail on the back. Tendons linked up the vertebrae of the back and tail, which would have reduced mobility of the spine. The gut was large and long, a long digestive tract was needed to process all the vegetation.

Neck

The neck is ‘s’ shaped, and the neck joins the skull at the very back.

Skin and spines

I. lakotaensis is thought to have been sail backed: the dorsal process of each individual vertebra was elongated, although not to the degree seen in more derived iguanodontids such as Ouranosaurus. Each vertebral spine would have been joined to the next by tendons and soft tissues, to form a continuous sail along the back. The sail started abruptly behind the neck (above the arms) where it was highest, and tapered gently backwards to the tail tip. Each dorsal (back) vertebra spine was about double the length of those figured. The only other notable feature is the thumb spike. This was conical and pointed. It would have been slightly longer and sharper in life, due to the presence of a keratin sheath. The skin was a rough texture, made up of a mosaic of small pebble-like scales.

Primary references

DiCroce, T. and Carpenter, K. (2001). New Ornithopod from the Cedar Mountain Formation (Lower Cretaceous) of Eastern Utah. In: Tanke, D.H. and Carpenter, K. (Eds). Mesozoic Vertebrate Life: New Research inspired by the Paleontology of Philip J. Currie, Indiana University Press, Bloomington & Indianapolis, Indiana, p.183-196.

Martill, D. M. and Naish, D. 2001. Dinosaurs of the Isle of Wight. The Palaeontological Association.

Norman, D. B. 1980. On the ornithischian dinosaur Iguanodon bernissartensis from the Lower Cretaceous of Bernissart (Belgium). Mémoires de l’Institut Royal des Sciences Naturelles de Belgique, 178, 105pp.

Norman, D. B. 1986. On the Anatomy of Iguanodon atherfieldensis (Ornithischia: Ornithopoda). Bull. Inst. r. Sci. nat. Belg.: Sciences de la Terre, 56, 281-372.

Norman, D. B. 1998. On Asian ornithopods (Dinosauria: Ornithischia). 3. A new species of iguanodontid dinosaur. Zoological Journal of the Linnean Society. 122: 291-348.

Weishampel, D.B. & Bjork, P.R., 1989. The first indisputable remains of Iguanodon (Ornithischia: Ornithopoda) from North America: Iguanodon lakotaensis, sp. nov. Journal of Vertebrate Paleontology 9(1):56-66