Was the Tyrannosaurus Rex a foodie?
The dinosaur, fixed in the popular imagination as a ruthless predator that chomped on whatever unfortunate creature crossed its path, actually had a jaw bristling with nerve endings that made it a more judicious eater than previously known, according to paleontologists in Japan who published their findings in Historical Biology on Monday.
While it might not have been a truly discerning gastronome, the T. Rex had a sophisticated mandible comparable to the jaws of modern-day crocodiles and tactile-foraging birds, like ducks, according to the scientists from the Institute of Dinosaur Research at Fukui Prefectural University, who conducted the study.
In other words, T. Rex very likely did not eat blindly, according to the study. It had keen senses that might have allowed it to recognize different parts of its prey and to chew on them differently depending on what it was munching on.
“The jaws of Tyrannosaurus were powerful enough to crush bones,” Soichiro Kawabe, one of the authors of the study and a paleontologist at the institute, said in an email. “However, in situations where food was plentiful, they may have used their sensitive snouts to eat the more nutritious parts of their prey selectively. The diet of Tyrannosaurus may not have been as crude as we imagine.”
The study does not say how discriminating the T. Rex was or whether it could recognize the difference between bone and flesh.
“These speculations are pretty imaginary and not within the scope of what we can scientifically derive from our research results,” Dr. Kawabe said.
The significance of the study is that it reveals the complex development of nerves within the mandible of the Tyrannosaurus, he said.
“Based on the morphology of the mandibular nerve of Tyrannosaurus, we were able to clarify that the jaw tip of Tyrannosaurus was most likely a pretty capable sensor,” Dr. Kawabe said.
Dr. Kawabe and another scientist, Soki Hattori, an assistant professor at the institute, used computed tomography, or CT scanning, to analyze and reconstruct the canal structure of the jawbone through which nerves and blood vessels would have passed. They studied the fossil of a T. Rex found in the Hell Creek Formation in Montana.
The fossil was well preserved, allowing the researchers to study the canal structure, he said.
The sensitive jaw tips also give clues to how the Tyrannosaurus may have parented.
Crocodiles have sensitive snouts, which help them detect prey in water but also give them such a finely tuned sense of touch that they can carry their young in their mouths without crushing them with their powerful jaws.
“Tyrannosaurus may have done the same,” Dr. Kawabe said.
The study underscores “the sensitive side of the T. Rex,” said Jack Tseng, a paleontologist at the University of California, Berkeley, who read the report.
“We’ve been really obsessed with the forces that the T. Rex could possess rather than its finesse,” he said. “This gives us a sense of its finesse.”
The report gives “another dimension” to a creature that the general public has obsessed over but rarely perceived as anything more than a monster, said Dr. Tseng, who has analyzed the bite of teenage Tyrannosaurus.
“They were not blockheads that were chomping down on anything they saw moving,” he said.
Still, Dr. Tseng said the study’s findings underscore the need for more fossil evidence to show how the dinosaur’s sensitive mandible was used. Analyzing coprolites, or fossilized feces, “could be another way to understand how sensitive their palate was,” he said.
The authors of the report acknowledged that their findings are limited: They did not analyze the full mandible area of the dinosaur or use other dinosaur fossils for comparison.
“Ideally, this study can be continued with a variety of additional types of dinosaurs, to see if Tyrannosaurus was truly exceptional, or just a run-of-the-mill carnivorous dinosaur,” said Thomas R. Holtz, a paleontologist at the University of Maryland who read the study. “But even this smaller scale study helps us better understand dinosaurs as living, feeling animals.”