How Iguanodon chewed its food
Apart from the homy beak that was able to nip off plants at the front end of the mouth, the sides of the jaws are lined with a formidable, nearly parallel array of chisel-like teeth that form irregularly edged blades (Figure 26). Each working tooth slots neatly against its neighbours in a rank-and-file arrangement, and beneath the working teeth are replacement crowns that will slot mto place as the working teeth are worn away, forming what is in effect a ‘magazine’, or battery, of teeth. This continuous replacement pattern is normal for reptiles in general. What is unusual, even by reptile standards, is that the working and replacement teeth are held together in an ever-growing magazine as if they were all contributing to one giant, grindstone-like tooth. Wear between opposing (upper and lower) magazines maintains a grinding surface throughout the life of the dinosaur. Dinosaur costume Rather than having permanent, hard-wearing grinders (as we do), this could be described as a disposable model that relies on constant replacement of individually simpler teeth.
Opposing edges of each cutting blade of teeth have characteristics that ensure efficiency in their cutting action. The inner surfaces of the lower teeth are coated in a thick layer of extremely hard enamel, while the remainder of the tooth is made of softer, bone-like dentine. Walking dinosaur costume In contrast, the upper teeth have the reverse arrangement: the outer edge being coated in thick enamel and the remainder of the tooth is composed of dentine. When the jaws are closed, these opposing blades slide past each other: the hard, enamelled leading edge of the lower jaw magazine meets the enamelled cutting edge of the upper teeth in a cutting/ shearing action rather like the blades of a pair of scissors (Figure 27). Once the enamelled edges have passed one another, the enamel edges (unlike scissor blades) then cut against the less resistant dentine parts of opposing magazines in a tearing and grinding action, which is ideal for crushing up tough plant fibres.