Complex Dental Structure and Wear Biomechanics in Hadrosaurid Dinosaurs

Abstract

Mammalian grinding dentitions are composed of four major tissues that wear differentially, creating coarse surfaces for pulverizing tough plants and liberating nutrients. Although such dentition evolved repeatedly in mammals (such as horses, bison, and elephants), a similar innovation occurred much earlier (~85 million years ago) within the duck-billed dinosaur group Hadrosauridae, fueling their 35-million-year occupation of Laurasian megaherbivorous niches. How this complexity was achieved is unknown, as reptilian teeth are generally two-tissue structures presumably lacking biomechanical attributes for grinding. Here we show that hadrosaurids broke from the primitive reptilian archetype and evolved a six-tissue dental composition that is among the most sophisticated known. Three-dimensional wear models incorporating fossilized wear properties reveal how these tissues interacted for grinding and ecological specialization.

The Functional and Palaeoecological Implications of Tooth Morphology and Wear for the Megaherbivorous Dinosaurs from the Dinosaur Park Formation (Upper Campanian) of Alberta, Canada

“…For this reason, we examined dentine microwear. Preliminary investigation confirmed that both mantle dentine and orthodentine are exposed on wear facets [36]. The former is characterized by its resistance to wear, causing it to stand proud of the softer orthodentine, which wears more readily to produce a concavity on the occlusal surface [36].…”

“…Preliminary investigation confirmed that both mantle dentine and orthodentine are exposed on wear facets [36]. The former is characterized by its resistance to wear, causing it to stand proud of the softer orthodentine, which wears more readily to produce a concavity on the occlusal surface [36]. Despite these mechanical differences, examination of microwear revealed that individual features are continuous across the boundary of these two tissues.…”

Dental macro- and microwear in Carinodens belgicus, a small mosasaur from the type Maastrichtian

“…Though bite forces can allow materials of lesser hardness to indent a harder solid, this is far less likely a cause than indentation by materials of greater or equal material hardness. The hardness of squamate enamel is not yet known, but the likely value of its hardness is somewhere between that of pure apatite (Dietrich, 1969) and mammalian enamel (Cuy et al, 2002;Xu et al, 1998) , and may be similar to that of estimates made for the enamel of some archosaurs (Erickson et al, 2012). Mosasaur enamel is known to have a structure that may allow some specialisations to avoid fracture such as modifications to its thickness (Sander, 1999), but it is not prismatic like mammalian enamel and may not be as resistant to indentation and more prone to fracture.…”

Dental abrasion as a cutting process

“…This is particularly important when conventional 'CoulombAmontons' estimates tend to show that the coefficient of friction varies with groove depth [71]. However, some theoretical approaches to abrasive wear have ignored such complications, leaning heavily on theory from static tests [74], and these have recently been applied to dental abrasion studies [75].…”