Archaeological discoveries have changed what we know about tyrannosaurs—they had feathers and ran like birds. Now, a new species that roamed in Montana 100 million to 66 million years ago has given us our first insight into what these dinosaurs’ faces might have looked like.
A typical Daspletosaurus hornei is about 30 feet long and 7 feet tall, with a large skull covered in bony ridges and different skin types, according to Thomas Carr, a paleontologist from Carthage College, and his team.
In their paper in Scientific Reports , they write that D. horneri is “critical to understanding the evolutionary transition from non-beak to beak along the line to birds, since beaks are specialized epidermal structures,” meaning the skull gives us a glimpse at the in-between stages between snouts and beaks.
Researchers examined the textures of a well-preserved skull and reconstructed what kinds of tissues and systems of nerves covered them. They also had access to a massive database of tyrannosaur bones that they used for comparison to rule out any damage that might have happened during fossilization.
Once the researchers completed their texture analysis, they compared it to modern animals who show nearly identical patterns: birds and crocodiles. Here’s Annalee Newitz reporting for Ars Technica:
Immediately, they found that the tyrannosaur’s lower jaw showed evidence of having “neurovasculature that is also seen in birds.” Specifically, it seems that D. horneri had a trigeminal nerve, an ancient piece of anatomy found in many animals whose faces are highly sensitive to vibration, infrared radiation, electricity, and even magnetic fields.
The trigeminal nerve would have been connected to a highly sensitive flat scale on the dinosaur’s nose and around its mouth. Each of these scales would’ve been densely packed with nerves—integumentary sensory organs (ISOs)—that could transmit “high resolution tactile sensations from the skin, making their snouts more sensitive than human fingerprints.”
According to the researchers, ISOs might’ve helped in a variety of ways. They could have helped tyrannosaurs detect optimal nest temperatures, harmlessly pick up eggs, and even engage in foreplay. During courtship, they might have rubbed their sensitive faces together to stimulate those nerve endings. That such hulking creatures could engage in such subtle sexual behavior is remarkable, and may suggest that we have a lot more to learn about these ancient beasts.
Photo credit: Patrick Emerson / Flickr (CC BY-ND 2.0)