Even flossing wouldn't have helped

Science News, Oct 20, 2001

Small particles trapped in minuscule cracks or pits in the fossilized teeth of some plant-eating dinosaurs could give scientists a way to identify what types of greenery the ancient herbivores munched.

Many types of plants produce phytoliths--literally, plant stones--in their stems and leaves by converting the silica dissolved in groundwater into a crystalline form similar to opals. These tiny parcels of grit come in a wide variety of shapes and sizes, and they have a microscopic structure different from that in silica crystals formed by geologic processes, says David A. Krauss, a paleobiologist at Boston College.

Because they're harder than tooth enamel, phytoliths scratch tooth surfaces and can become embedded in small cracks there. Krauss examined a collection of teeth from hadrosaurs and ceratopsians--two different groups of plant-eating dinosaurs--unearthed in Dinosaur Provincial Park in Alberta, Canada. He found that about 25 percent of these teeth had phytoliths trapped in the chewing surfaces.

Different types of plants produce phytoliths that look alike, but some groups of species generate distinct crystal forms. Krauss analyzed the phytoliths produced by living relatives of the ancient plants found in the fossil layers holding the dinosaurs.

The sizes and shapes of crystals from the fossil teeth suggest that the ceratopsian dinosaurs, relatives of Triceratops, may have eaten a high proportion of tough-leafed cycads, whereas the hadrosaurs, or duck-billed dinosaurs, probably favored ferns. --S.P.