Jun 7, 2017

Rumors of T. Rex’s Feathery Past Were Greatly Exaggerated

Tyrannosaurus rex fossilized skin impression.
The first known fossilized skin impressions for Tyrannosaurus rex suggest that this gigantic carnivore, unlike many other dinosaurs, had little to no feathers.

The fossils, reported in the journal Biology Letters, show that T. rex was instead covered with a tough and scaly hide. Fossilized skin impressions for other tyrannosaurs — including Albertosaurus, Gorgosaurus, and Daspletosaurus — reveal that all such dinosaurs lacked feathers, too.

Co-author W. Scott Persons and his colleagues were thrilled when they first saw the T. rex remains, which preserve numerous patches of skin impressions from the dinosaur’s neck, pelvis, and tail.

“Mostly I couldn’t wait to touch it!” Persons said, referring to one such well-preserved fossil. “It is every kid’s dream to pet a T. rex, and — if we are honest — it is also every dinosaur paleontologist’s.”

“The skin is bumpy,” he continued. “None of the scales are as big as what you see on the back of a crocodile, but they are similar to the scales along a croc’s flank. I suppose tyrannosaur hide would make for a nice set of luggage.”

The T. rex remains were unearthed near the town of Baker, Montana, and date to the Late Cretaceous (100.5–66 million years ago). Lead author Phil Bell of the University of New England, Persons, and the rest of the international team examined the fossils in detail. The resulting information, combined with observations of the other dinosaur remains, allowed the researchers to assemble a new dataset concerning both tyrannosaur skin and overall body size.

The scientists note that the wolf and lion-sized ancestors of tyrannosaurs were among the first carnivorous dinosaurs to be discovered with feathered, rather than scaled, skin. Over the course of evolution, many in the lineage must have therefore lost their feathers.

Persons said that the feather coats of the tyrannosaur ancestors probably served as insulation to hold in body heat. As T. rex and certain other tyrannosaurs grew ever larger over time, their need for feathers probably diminished.

Tyrannosaur fossil skin impression.
“Today we see that many big mammals — like elephants, rhinos, hippos, and Cape buffalo — have greatly reduced their covering of hair,” he explained. “As big bulky animals living in warm environments, these mammals are more concerned with the risk of overheating than the challenge of staying warm, so they are better off with little to no hair. The same explanation probably explains, at least in part, why big tyrannosaurids had little to no feathers.”

T. rex, which could grow to about 40 feet long and 20 feet tall, had very long legs and strong leg bones. These indicate that it could move quickly when it wanted to do so.

“In a sprint, it could probably out-run any other large dinosaur,” Persons said.

T. rex, as well as other tyrannosaurs, lived in a range of habitats, from swamps to open floodplains. During the day, these regions could become very hot. A large animal with an active lifestyle living in an often-hot environment was then “better off not wearing a down jacket,” Persons said.

Exchanging such a feathery covering for a scaly hide meant that T. rex and its kind were covered in skin that was tough and resistant to abrasion, the researchers believe.

Persons is currently investing still more new T. rex fossils, this time from Saskatchewan, Canada. Instead of focusing on the skin, he is examining the enormous dinosaur’s skull, and what it reveals about the carnivore’s face.

Read more at Discovery News

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