The strong but sensitive type
Fossils from a relative of the ferocious Tyrannosaurus rex led scientists to a fascinating conclusion recently: these powerful beasts had snouts with scales as sensitive as human fingertips.
The ancestor The Daspletosaurus horneri lived about 75 million years ago. Its bones were discovered in 1989, and scientists say it appears the animal is an ancestor of the Tyrannosaurus rex. The Daspletosaurus, which was smaller than T. rex at about nine metres long and two metres tall, died off more than 10 million years before the T. rex appeared. Scientists believe the Daspletosaurus horneri, which means “Horner’s frightful lizard,” had something in common with all tyrannosaurs — many small, sensitive nerve openings in its snout.
The bones The fossils of the Daspletosaurus horneri — initially a piece of the snout, and later a complete skull and other specimens including a skeleton — were found in northwestern Montana and southern Alberta by American paleontologists. Among them was a team working under the auspices of Montana’s Museum of the Rockies. The remains were found in the same geological layer, the Two Medicine Formation, a deposit dating back to the late Cretaceous period, about 65 million to 145 million years ago.
Into the groove Based on research that flowed from the discovery of the Daspletosaurus horneri fossils, scientists found grooves and canals left by blood vessels and nerves in the snout area. From this, experts have deduced that these animals had a network of very sensitive nerves that would have connected to the scales of their snout. “Its surface tissue would have been like the human hand, very tough but sensitive, likely more so,” says one of the experts, Jayc Sedlmayr, an assistant professor of cell biology and anatomy with Louisiana State University’s Health Sciences Center.
Similar creatures A key to the research is anatomical similarities between dinosaurs and their two most common living relatives: birds and crocodilians. Sedlmayr had dissected crocodiles, alligators and birds and knew that sensi- tivity in the snout and beak area is due to stimulation from a special nerve, the trigeminal nerve.
The Daspletosaurus horneri and other tyrannosaurs also had this nerve, says Thomas Carr, a director at the institute of paleontology at Carthage College in Wisconsin, and head of the team studying the Daspletosaurus.
Food and foreplay The nerves in the snouts of crocodil- ians and tyrannosaurs and in birds’ beaks are about as sensitive as human fingertips and lips. Researchers believe these dinosaurs used this sensitivity to locate prey, compete for food and, during mating rituals, touching the snouts of other tyrannosaurs while nuzzling. And despite the fact that tyrannosaurs were large and deadly land predators, just as alligators place their young in their jaws to carry and protect them, tyrannosaurs likely did the same.