A newly discovered species of Tyrannosaurus, a relative of T. rex, has revealed a surprising feature that may have been shared among this group of Cretaceous carnivores: a remarkably sensitive face.
Standing at more than 2m (6ft) high and 9m (29ft) long, the carnivorous Daspletosaurus horneri – which means Horner's frightful lizard – would have been a fearsome predator. Its sensitive facial scales may have added to its brutal efficiency at hunting and killing prey, reveals a study published in the journal Scientific Reports.
The fossil remains of several adults and juveniles of the species Daspletosaurus horneri were unearthed in Montana, US. It is thought to have lived there about 75 million years ago and was one of the last of its kind to have evolved in what is now the western US.
Examining the skulls and skeletons from several adults and juveniles of the species, researchers were able to start to piece together what the tyrannosaur would have looked like.
But looking at bones can only get you so far when reconstructing a dinosaur's appearance. The specimens' soft tissue was not preserved by fossilisation. The palaeontologists were able to team up with scientists studying the anatomy of modern-day dinosaur relatives to hone in on what these lost tissues were like.
Dissection of birds – sometimes called ''living dinosaurs'' – and crocodilians helped to shed light on the facial structure of the tyrannosaur. The presence of many holes in the skull, called foramina, showed that the tyrannosaur had many nerves and blood vessels passing through to the soft tissues surrounding it.
A rich supply of blood and nerves to the tissues suggests that the dinosaur's facial skin and scales were very sensitive, helping it to identify objects.
"In some ways, the facial components of the trigeminal nerve of these dinosaurs mirrors that of humans," said study author Jayc Sedlmayr, an anatomist at Louisiana State University Health Sciences Centre.
"The human trigeminal nerve provides significant touch sensitivity to the face. It brings back sensation from our facial muscles, allowing us to fine tune and coordinate the emotional and social displays so important to human communication."
Daspletosaurus horneri is also thought to have had large, flat scales covering its face, patches of armour-like skin, and no lips.
"It turns out that tyrannosaurs are identical to crocodilians in that the bones of their snouts and jaws are rough, except for a narrow band of smooth bone along the tooth row," said study author Thomas Carr of Carthage College.
"In crocodilians, the rough texture occurs on deep to large flat scales; given the identical texture, tyrannosaurs had the same covering. We did not find any evidence for lips in tyrannosaurs, the rough texture covered by scales extends nearly to the tooth row, providing no space for lips."