Thanks to movies, we probably all have the same mental picture of the terrifying Tyrannosaurus Rex, but new research has revealed that the creatures had a sensitive side. We already know that they probably didn't bellow bone-rattling roars but cooed like doves instead, and now their hard-nosed image has taken another hit with the discovery of a new related species that shows their snouts were as sensitive as our fingertips, to help them build nests and nuzzle their young.

Although Tyrannosaurus Rex is arguably the most well-known dinosaur ever, it's just one species in a group collectively known as the tyrannosaurs. New details are regularly dug up on the animals, including the fact that they may have grown much bigger than was previously assumed, and now Daspletosaurus horneri joins the family – and it has some secrets to spill.

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The name means "Horner's Frightful Lizard," after the influential palaeontologist, Jack Horner (not the kid in the corner eating pie). By analyzing the texture of the bone in its skull, scientists were able to infer the different types of skin it would have had on its face, including patches of protective "armor" and more sensitive areas that would have allowed the animals to use their snouts to interact with their surroundings, to compensate for their laughably little arms.

"Being a tyrannosaur, they had really small arms," says Jason Moore, co-author of the study. "They wouldn't be able to interact with their environment with their hands the way mammals do — find food, build nests, tend to eggs and young. In order to do these things, Daspletosaurus needed to use its feet or head. The discovery and analysis of the tyrannosaur shows that the dinosaur had a developed face sensitivity similar to the sensitivity in our finger tips, suggesting it could use its snout for all those complex ecological interactions, similar to the way crocodiles do today."

Holes in the snout and jaws of the tyrannosaur skulls would have allowed bundles of nerves to pass through and reach the skin. According to the researchers, the sensitivity that would allow fits into the wider context of unusual facial senses that different animals have evolved.

"The trigeminal nerve has an extraordinary evolutionary history of developing into wildly different 'sixth senses' in different vertebrates, such as sensing magnetic fields for bird migration, electroreception for predation in the platypus bill or the whisker pits of dolphins, sensing infrared in pit vipers to identify prey, guiding movements in mammals through the use of whiskers, sensing vibrations through the water by alligators and turning the elephant trunk into a sensitive 'hand' similar to what has been done to the entire face of tyrannosaurs," says Jayc Sedlmayr, co-author of the study.

Rough bone across most of their face suggests the tyrannosaurs' heads were mostly covered in large, flat scales. That texture gets particularly bumpy around the tip of the snout and on the sides of the lower jaws, which the researchers say is an indication that those areas once sported a thicker armor-like coating, to protect the animal from harm.

"It turns out that tyrannosaurs are identical to crocodylians in that the bones of their snouts and jaws are rough, except for a narrow band of smooth bone along the tooth row," says Thomas Carr, lead researcher on the study. "We did find evidence for other types of skin on the face, including areas of extremely coarse bone that supported armor-like skin on the snout and on the sides of the lower jaws. The armor-like skin would have protected tyrannosaurs from abrasions, perhaps sustained when hunting and feeding."

Radiometric dating indicates that Daspletosaurus horneri joins the family as the youngest tyrannosaur, evolving from Daspletosaurus torosus over a period of about 2.3 million years.

"Daspletosaurus horneri was the youngest, and last, of its lineage that lived after its closest relative, D. torosus, which is found in Alberta, Canada," says Carr. "The geographic proximity of these species and their sequential occurrence suggests that they represent a single lineage where D. torosus has evolved into D. horneri."

The research was published in the journal Scientific Reports.

Source: University of New Mexico

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