Chuck Bednar for redOrbit.com – Your Universe Online
An ancient, bison-sized rodent likely used its massive incisors like elephant tusks, experts from the University of York and The Hull York Medical School (HYMS) claim in a new study.
As the researchers report in Wednesday’s online edition of the Journal of Anatomy, the creature, Josephoartigasia monesi, was a rodent that is a close cousin of the guinea pig and lived in South America approximately three million years ago.
It is the largest fossil rodent ever discovered, with an estimated body mass of 1000 kilograms (2200 pounds). Affectionately dubbed “Ratzilla” by freelance journalist Sid Perkins in an article published by Science, the creature is believed to be the largest rodent to have ever lived.
It also had gigantic and extremely powerful front teeth, according to Dr. Philip Cox.
Dr. Cox, a member of the Centre for Anatomical and Human Sciences (a joint research center run by the York Department of Archaeology and HYMS) used computer simulations to see just how powerful the bite of Josephoartigasia might have been.
While the bite forces would have been tremendous (approximately 1400 newtons, similar to that of a tiger), the researchers found that the incisors would have been robust enough to withstand nearly three times that force – an indication that the teeth may have been used for other purposes.
Perkins said that it is possible that this “megarodent” used its front teeth to dig up roots, to protect itself against predators, or as a weapon during battles over potential mates or territory, just as modern elephants do. A future analysis of microwear patterns on Josephoartigasia’s teeth may provide more information about the creature’s dietary habits, he added.
The research was conducted using CT scans of the specimen’s 53-centimeter-long skull, which was first described less than 10 years ago. Dr. Cox and his colleagues used that data to create a virtual reconstruction of the skull, then subjected it to finite element analysis, an technique used to predict stress and strain in a complex geometric object.
The software used in the process is the same used to analyze stress in airplane parts, Perkins said, and they modeled the lower jaw based on a close modern-day relative, the chinchilla. Based on the simulations, the researchers measured the overall bite force of the Josephoartigasia at 4,165 newtons, three times that of a crocodile, but just 1,400 at the tips of its front teeth.
“Predicted stresses across the skull were only minimally affected by changes to muscle forces and orientations, but revealed a reasonable safety factor in the strength of the skull,” the study authors wrote. “These results, combined with previous work, lead us to speculate that J. monesi was behaving in an elephant-like manner, using its incisors like tusks, and processing tough vegetation with large bite forces at the cheek teeth.”
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