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American Association for the Advancement of Science

Some dinos' teeth rivaled mammals' for plant-chewing

Horse-like chewing surface in a hadrosaurid dental battery. The crests and basins form through differential wear of the dental tissues.
[Image courtesy of Gregory M. Erickson, Ph. D., Florida State University]

The teeth of duck-billed dinosaurs called "hadrosaurids" were far more complex than those of other reptiles, according to a new study. In fact, they were much more like the teeth of horses, bison or elephants, which are built for grinding tough, gritty plant material, the researchers say.

The hadrosaurids were large herbivores that were common during the Late Cretaceous period, about 66 to 100 million years ago. With broad, duck-like bills, they grazed on horsetail, fern and primitive angiosperm groundcover and browsed on conifers. These tough plants were covered with hard, tooth-scouring particles. Fossils have shown that hadrosaurids chewed these plants using teeth with flattened grinding surfaces, like the those on horse or bison teeth.

The grinding teeth of these mammals are pretty complex, with several different tissue types of varying hardness. This combination of materials helps maintain the small ridges and valleys on the tooth's surface, protecting them from breaking or wearing down. Most reptile teeth are much simpler, with only two types of tissue.

Gregory Erickson of Florida State University and colleagues analyzed fossil hadrosaurid teeth and show that they were in fact composed of six types of tissue and were among the most complex of any known animal teeth. The hadrosaurids thus appear to have been well-equipped for their diets of tough plants, which may help explain why they were such common dinosaurs.

The research appears in the 4 October issue of the journal Science.