Duck-billed dinosaurs were the Cuisinarts of the Late Cretaceous period, pulverizing tough, gritty plants such as conifer trees using hundreds of rough, interlocking teeth (shown). Now, scientists have figured out how the herbivores developed their complex chompers: The animals' teeth contained six types of tissue that wore down to differing degrees, creating distinctive peaks and valleys. The surface of the duck-billed dinos' teeth resembles that of horses and other modern grazers that have four main types of tooth tissue.
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