A species of carnivorous dinosaur that once roamed Madagascar 70 million years ago was so tough on its teeth that they needed to be replaced frequently, according to a new study.
Majungasaurus had to replace its mouth full of teeth about every two months, growing replacements in each socket anywhere from two to 13 times faster than other meat-eating dinosaurs, the researchers found. The in the journal PLOS ONE.
"This meant they were wearing down on their teeth quickly, possibly because they were gnawing on bones," said Michael D'Emic, study author and assistant professor of biology at Adelphi University in New York. "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."
Majungasaurus was around 21 feet long and reigned supreme at the top of the food chain on Madagascar. It's sharp teeth could slice like knives through the flesh of its prey. It also had a short snout and a horn jutting up from the top of its head.
But its teeth, meant for ripping through flesh, weren't so great when they encountered bone. Chewing on bones, something that some animals like rodents do, can provide them with some nutrients otherwise lacking from their diets.
"That's our working hypothesis for why they had such elevated rates of replacement," D'Emic said.
The rate of tooth growth was so rapid that it lines up with the quick ability sharks have of replacing their teeth -- as well as the large herbivore dinosaurs, he said.
Researchers analyzed growth rings on the teeth of Majungasaurus. They act like the rings of a tree, but instead of recording a year, the rings actually record a single day.
This analysis was compared with computerized tomography on its jaws to look at teeth growing inside them. Combined, this data revealed how quickly the dinosaurs could replace their teeth.
This time-consuming analysis of teeth replacement has only occurred in a few of the hundreds of carnivorous dinosaurs that were once spread across the globe. During their study, the researchers also looked at growth patterns for other dinosaurs like Allosaurus and Certosaurus.
"I'm hoping this latest project spurs more people to study other species. I bet that will reveal further surprises," D'Emic said. "And hopefully that will lead to a better understanding of how dinosaurs evolved to be successful for so long."
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