研究人員說,，長著鴨嘴的鴨嘴龍恐龍的牙齒要比其它爬行動物的牙齒復(fù)雜得多，它們牙齒對磨碎堅(jiān)韌,、沙礫般的植物性材料的能力可與馬或野牛的牙齒相媲美,。
鴨嘴龍是晚白堊世時在歐洲,、亞洲及北美占主導(dǎo)地位的大型食草動物。它們用寬闊的鴨子樣的喙進(jìn)食問荊,、蕨類植物及原始的被子植物性地被并會吃針葉樹,。這些堅(jiān)韌、富含纖維素的植物覆蓋有堅(jiān)硬的,、摩擦牙齒的顆粒,，而這些鴨嘴龍用其類似于馬和野牛牙齒的帶有平磨面的齒列來咀嚼它們。
這些哺乳動物的磨牙相對較復(fù)雜,，帶有數(shù)種不同的組織類型,，但爬行動物通常擁有簡單的，只有2種組織類型的牙齒,，這些組織為： 硬琺瑯質(zhì)及一種較軟,、骨頭樣的材料。Gregory Erickson及其同事分析了鴨嘴龍牙齒的化石并顯示它們實(shí)際上是由6種組織組成的,，而且屬于那些任何已知動物中最復(fù)雜的牙齒,。
不同組織的分布在每個牙齒內(nèi)也有相當(dāng)大的差異，從而暴露出隨著牙齒在跨越咀嚼面所進(jìn)行遷移時的不同的構(gòu)造,。文章的作者說,，這使得某一單顆的牙齒能夠在其發(fā)展的過程中呈現(xiàn)不同的形式和功能，并可能促成了鴨嘴龍的成功的適應(yīng)性發(fā)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.
