Meat-eating dinosaur replaced its teeth like a shark
New research led by Michael D. D'Emic, an assistant professor of biology at Adelphi University, indicates that a 70-million-year-old dinosaur shed and replaced its teeth like a shark about every two months. Native to what is now the island of Madagascar, Majungasaurus replaced its teeth up to 13 times faster than other carnivorous dinosaurs.
Bones are a very good source of various nutrients, so it isn't surprising that many animals gnaw on them. Unfortunately, bones tend to be on the hard side, which means that they're hard on the teeth.
To overcome this, animals have evolved a number of different strategies. One is to have very hard teeth that can stand up to a lifetime of wear without getting too blunted. Another is the one used by rodents, which is to have teeth that keep growing in as they're worn down. And there's the strategy used by sharks and dinosaurs like Majungasaurus, which replace their teeth on a regular basis.
By looking at the wear patterns on the teeth of Majungasaurus and comparing them to those of two other carnivorous dinosaurs, Allosaurus and Ceratosaurus, the researchers found the relatively soft teeth of Majungasaurus had microscopic growth rings like those of a tree, except that they were deposited daily rather than annually. They also looked at computerized tomography (CT) of intact Majungasaurus jaws to see unerupted teeth and estimate their replacement rate, which turned out to be one new tooth per socket every two months.
"This meant they were wearing down on their teeth quickly, possibly because they were gnawing on bones," says D'Emic. "There is independent evidence for this in the form of scratches and gouges that match the spacing and size of their teeth on a variety of bones – bones from animals that would have been their prey."
The study was published in PLOS ONE.