July 18, 2013
Teeth Continuously Replaced In Large Sauropod Dinosaurs
[Watch Video: CT Scan Of A Diplodocus Tooth]
Brett Smith for redOrbit.com - Your Universe Online
According to a new report, published in the open access journal PLoS ONE, two sauropods, Diplodocus and Camarasaurus, produced new teeth on a monthly basis and had several backup teeth constantly stored in their jaws.
"A nearly 100-foot-long sauropod would have had a fresh tooth in each position about every one to two months, sometimes less," said report co-author Michael D'Emic, from Stony Brook University in New York.
In the study, D'Emic and several other American researchers searched tens of museum collections for sauropod jaws. After negotiating with several museums about gaining access to their specimens, the team was finally able to procure a Camarasaurus jaw from Utah and a Diplodocus jaw from Colorado.
The team then deliberately and painstakingly cracked open the jaws and removed visible teeth as well as backup teeth that were embedded in the sockets below.
"That had to be done by a professional, somebody with a surgeon's hands and patience," D'Emic told the Los Angeles Times.
To remove the teeth, set them in a special resin, mount them on slides, polish them by hand and then photograph them for study -- took researchers six months.
After removing all the teeth, the paleontologists found that their Camarasaurus had three backup teeth and Diplodocus had five spares behind each visible tooth. In addition to counting teeth, the team said they were also interested in finding out how rapidly each tooth came in.
Using CT images taken at the University of Michigan's Canton Health Center, the team looked at each tooth's dentin, the level just below the enamel. Counting layers of dentin like rings in a tree stump, the researchers were able to determine the age of each individual tooth. By looking at the intervals between teeth in a jaw socket, they could also figure out how rapidly teeth were replaced.
According to the report, Camarasaurus, had a new tooth about once every two months and Diplodocus had a replacement about once a month.
Because the massive sauropods only used their teeth to cut their leafy food from a plant before swallowing it whole, having teeth turn over faster kept them fresh for trimming off trees or bushes, D'Emic said.
Additionally, if the massive dinosaurs ate food that grew close to the ground -- they would have exposed their teeth to coarse and damaging soil on a regular basis, D'Emic said.
Sauropod expert Paul Sereno, from the University of Chicago, told the Times that he tended to agree with D'Emic's argument.
"Last night I had a salad that I grew in my own yard for the first time, and I really had to wash the lettuce carefully, because there's this grit in it," said Sereno, who was not directly involved in the study. "It's exactly what we're talking about. You put your muzzle down to the ground and you're going to be incorporating these sand grits that wear your teeth down."