研究人员说，长着鸭嘴的鸭嘴龙恐龙的牙齿要比其它爬行动物的牙齿复杂得多，它们牙齿对磨碎坚韧、沙砾般的植物性材料的能力可与马或野牛的牙齿相媲美。
鸭嘴龙是晚白垩世时在欧洲、亚洲及北美占主导地位的大型食草动物。它们用宽阔的鸭子样的喙进食问荆、蕨类植物及原始的被子植物性地被并会吃针叶树。这些坚韧、富含纤维素的植物覆盖有坚硬的、摩擦牙齿的颗粒，而这些鸭嘴龙用其类似于马和野牛牙齿的带有平磨面的齿列来咀嚼它们。
这些哺乳动物的磨牙相对较复杂，带有数种不同的组织类型，但爬行动物通常拥有简单的，只有2种组织类型的牙齿，这些组织为： 硬珐琅质及一种较软、骨头样的材料。Gregory Erickson及其同事分析了鸭嘴龙牙齿的化石并显示它们实际上是由6种组织组成的，而且属于那些任何已知动物中最复杂的牙齿。
不同组织的分布在每个牙齿内也有相当大的差异，从而暴露出随着牙齿在跨越咀嚼面所进行迁移时的不同的构造。文章的作者说，这使得某一单颗的牙齿能够在其发展的过程中呈现不同的形式和功能，并可能促成了鸭嘴龙的成功的适应性发展。（生物谷Bioon.com）
doi: 10.1126/science.1224495
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Complex Dental Structure and Wear Biomechanics in Hadrosaurid Dinosaurs
Gregory M. Erickson, Brandon A. Krick, Matthew Hamilton, Gerald R. Bourne, Mark A. Norell, Erica Lilleodden, W. Gregory Sawyer
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.
