Hypothesized distributions of nerves in Tyrannosaurus' mandible (orange). Credit: Taylor & Francis
Tyrannosaurus Rex was more than just a large beast with a big bite. It also had nerve sensors in its jaws that enabled it to detect and eat prey better, according to a study in Historical Biology Today.
Dr. Soichiro Kawabe from Fukui Prefectural University in Japan, the lead author, says that T. rex was a more terrifying predator than we thought.
"Our findings indicate that the nerves of Tyrannosaurus' mandible (an area in the jaw) are more complexly distributed than any other dinosaurs. They are comparable to modern-day crocodiles or tactile-foraging birds which have very keen senses.
This means that T. rex was sensitive for slight variations in material and movement. It indicates that T. rex could recognize different parts of its prey and be able to eat them differently depending upon the situation.
"This changes our perception of T. Rex as a dinosaur, insensitive around its mouth and biting at everything, even bones.
While the morphology and nerves of the jaws have been studied in many fossil reptiles as well, this is the first study of the mandible structure of T. rex.
Dr. Kawabe was joined by Dr. Soki Harttori Assistant Professor at Institute of Dinosaur Research to use computed tomography to analyze and reconstruct the distribution nervevascular canal of a T. rex fossil mandible. This was originally discovered in Montana's Hell Creek Formation.
The reconstruction was then compared to that of other dinosaurs like Triceratops as well as living birds and crocodiles.
The researchers were able to describe the well preserved canals that house the nerves and vessels in the dentary of Tyrannosaurus.
Dr. Kawabe says that the present study revealed complex branching of neurovascular canals in Tyrannosaurus' lower jaw, particularly in the anterior region. It is also assumed that there would be a similar branching neurovascular channel in Tyrannosaurus' upper jaw.
He said: "The neurovascular canal has a branching pattern as complex and extant as that of the extant Crocodilians, ducks, and crocodilians suggests that Tyrannosaurus' trigeminal nervous systems probably served as a sensitive sensor within the snout.
"It is important to note that Tyrannosaurus's sensitivity may have been less than that of crocodilians, because Tyrannosaurus does not possess the thick neural tissue that occupies the neurovascular canal like extant crocodiles.
"However, the sensitivity of Tyrannosaurus' snout was significantly higher than that of ornithischian dinos when they were compared in this study."
These results are consistent with the skull surface analysis of Daspletosaurus and neurovascular canal morphology in the maxilla from allosaurid Neovenator. This suggests that the facial area may have been very sensitive.
Dr. Hattori says that these inferences also suggest predation by tyrannosaurids. However, the jaw tips of tyrannosaurids were adapted to perform a variety of behaviors including nest construction, parental care and intraspecific communication.
The study has some limitations. T. rex's mandible area was not fully examined by the team. However, this is a small problem that "should be reasonable."
More information: Soichiro Kabe et. al. Complex neurovascular system within the dentary Tyrannosaurus. Historical Biology (2021). Soichiro Kawabe et al, Complex neurovascular system in the dentary of Tyrannosaurus,(2021). DOI: 10.1080/08912963.2021.1965137
