The world's greatest land predator may have been a nuzzler.
Tyrannosaurs, the "tyrant lizards" that once roamed the American West, are best known for their razor-sharp, banana-sized teeth, their crushing bite force and for terrorizing Jeff Goldblum and Sam Neill in "Jurassic Park."
But if a new study is correct, the massive meat-eaters may have employed a group of highly sensitive scales on their faces to help them eat, flirt and care for their young.
That's according to a group of scientists who just published a study on a group of fossils found in Montana. The group, led by Thomas Carr, of Carthage College in Wisconsin, studied the nearly intact skulls and other fragments of a new dinosaur species, this one called Daspletosaurus horneri, a member of the tyrannosaur family.
Carr and his team have concluded that among other traits, D. horneri may have had a group of scales along the sides and top of its snout that it used to sense things nearby. That conclusion was largely the work of evolutionary anatomist Dr. Jayc Sedlmayr, who teaches at the LSU Health Sciences Center in New Orleans and is a co-author of the report, published in Scientific Reports.
Sedlmayr's role in the project was to examine the bone fossils to try to determine what the D. horneri looked like by studying its closest living relatives: birds and crocodilian reptiles like alligators.
He noticed that the fossil skulls had bony canals that seemed to serve as protection for nerve bundles. Further, the number of these features was very similar to what is found in crocodiles, he said.
"These kinds of openings are associated with very sensitive nerve networks," Sedlmayr said.
Crocodiles have similar scales all over their bodies. They use them to sense nearby prey in the water and strike it, even in complete darkness. The scales also allow them to use crushing bite force when needed, but to gently carry their young when the adults need to move them, he said.
D. horneri, on the other hand, had the scales over only a limited area: the front, top and sides of the snout.
"Theirs is a face-based touch system more elaborate than a human hand," Sedlmayr said. That suggests the scales were used in more limited situations than crocodiles use theirs. The tyrannosaurs could have used their sensitive faces, for example, when eating, mating or caring for young.
"What we think is happening is it's used for social interactions," Sedlmayr said, referring to interactions with young or with potential mates.
"In the 500 million years of vertebrate evolution, tyrannosaurs are some of the most powerful land-living predators that ever existed," he said. Yet daspletosaurs may have had the same ability to delicately assist their young as their water-loving descendants do today.
The scales could also have assisted in another area: luring a lover.
"They could be used in sexual or mating rituals," Sedlmayr said. "Kind of a form of flirtation."
It may seem incongruous to picture these massive predators affectionately nuzzling each other in the wild, but that may have been exactly what happened, he said.
And even though the daspletosaurs are not the same species as T. rex, they are in the same family, and T. rex may have descended from the daspletosaurs, Sedlmayr said, meaning these types of facial touch abilities could have been found in all tyrannosaurs.
D. horneri, which lived about 75 million years ago, is an important fossil for a second reason. Its direct-line evolutionary ancestor is known and was found in the same area: Daspletosaurus torosos.
The two are a single-step progression on the evolutionary tree, something known as anagenesis. To find such evolutionary progression is very rare, Sedlmayr said.
"In many case, an organism will (develop into a new species), then diverge, and you'll get a branching pattern to the actual tree," he said. "This is an actual linear relationship. It's one to one, ancestor to descendant."