By most standards, Iguanodon (11 metres long and weighing about 3-4 tonnes) was a large herbivorous animal, and would have consumed plants in large quantities. Animatronic dinosaur Given this background information, questions about precisely how Iguanodon fed and assimilated its food can be explored in detail.
One persistent theory concerning its method of feeding was its suggested use of a long tongue to pull vegetation into the mouth. Animatronic dinosaur for sale This began with Gideon Mantell, who described one of the first, nearly complete lower jaws of Iguanodon. The new fossil included some tell-tale teeth, so the ownership could not be doubted, and it had a toothless, spout-shaped front end. Mantell speculated that the spout shape allowed a long tongue to slide in and out of the mouth, rather like a giraffe’s does. Mantell could not have known that the tip of the newly discovered lower jaw was incomplete and was capped by a predentary bone that filled in the ‘spout’.
It is very curious to note that in the 1920s Louis Dollo provided further support for Mantell’s conjecture. Walking dinosaur costume Dollo described a special opening in the predentary at the tip of the lower jaw; this formed a tunnel passing straight through the predentary bone that allowed a long, thin, muscular tongue to be projected outward to grasp vegetation and draw it into the mouth. Large bones (ceratobranchials) that had been found lying between the jaws of Iguanodon were suggested to act as the attachment for the muscles that would have operated this type of tongue. Such a structure fitted neatly with Dollo’s concept of Iguanodon as a high arboreal browser with a giraffe-like long, grasping tongue.
Careful re-examination of the lower jaws of a number of Iguanodon skulls from Bernissart failed to reveal Dollo’s predentary tunnel. The predentary has a sharp upper edge that supported a turtle-like horny beak. The predentary, and its beak, bit against the similarly toothless beak-covered premaxillae at the tip of the upper jaw, and this arrangement allowed these dinosaurs to very effectively crop the plants upon which they were feeding. The advantage of the horny beak was that it would have grown continuously (unlike teeth, which gradually wear away) no matter how tough and abrasive the plants that were being cropped. The ceratobranchial bones still require some explanation. In this instance, they would have been used to anchor the muscles that moved the tongue around the mouth to reposition the food as it was being chewed and for pushing the food back into the throat when it was ready to be swallowed. This is exactly the same role that is performed by the ceratobranchial bones in the floor of the human mouth.