T. Rex Was Likely Covered in Scales, Not Feathers

The research dispels theories that the fearsome dino boasted a feathery plume

T rex skin
Fossilized skin from the neck of a Tyrannosaurus rex. ©2004 Black Hills Institute of Geological Research, Inc., Hill City, SD

Tyrannosaurus rex​ has long been depicted with scaly, reptile-like skin. Over the past few decades, however, new research has called the accuracy of that portrayal into question. Evidence of feathers was discovered on the fossils of earlier tyrannosaurs, leading scientists to believe that the king of the dinos may have boasted fluffy plumage.

But as Jason Bittel reports for National Geographic, new research suggests that the T. rex of our favorite childhood movies may have not been too far from the truth. According to a study recently published in the journal Biology Letters, the T. rex’s skin was likely scaly.

An international team of researchers studied skin impressions taken from T. rex fossils found in Montana. They then compared those impressions to fossilized skin patches of other tryannosaurs, like the Albertosaurus, Daspletosaurus, Gorgosaurus, and Tarbosaurus. The samples represented parts of the dinosaurs’ stomach, chest, neck, pelvis, and tail, according to Ben Guarino of the Washington Post. And none bore any traces of feathers.

These findings indicate “that most (if not all) large-bodied tyrannosaurids were scaly,” the authors of the study write. They add that the T. rex may have had some feathers, but the plumage was likely limited to the dinosaur’s back.

Since there is ample evidence to suggest that earlier tryannosaurs had feathers, the study’s conclusions would mean that tyrannosaurs evolved a feathery coat, only to eventually lose it. The study’s authors believe that the T. rex’s size can help explain the evolutionary shift, Bittel reports.

T. rex were much bigger than their predecessors, having developed long legs that let them dash after prey. But large and active animals don't cool down as quickly as smaller creatures. So as they got bigger, researchers think that the dinosaurs may have lost their plumage. “[F]eathers were too much of a hindrance to cooling off after a sprint,” Bittel writes.  

There was, however, at least one massive tryannosaur that had feathers. The Yutyrannusdiscovered several years ago in China, stretched about 30 feet long and was covered in fine feathers. This dinosaur was smaller than the T. rex, but about the same size as the Albertosaurus and Gorgosaurus, which means that size can’t be the only factor that determines whether or not a dino sports a downy coat. So the authors of the study offer an additional hypothesis: the Yutyrannus had feathers because it lived in shady forests, which helped the dinosaur keep its cool.

A similar phenomenon can be seen in elephants of today, as Helen Briggs of the BBC points out. Asian elephants have more hair than African elephants not only because they are smaller, but also because they live in dense forest environments.

But the study’s findings are not conclusive. Soft tissues like feathers are only preserved in the fossil record under specific circumstances, so “[j]ust because we don't see them doesn't mean they weren't there,” Steve Brusatte of the University of Edinburgh told Briggs. So it is still possible that the most fearsome of all the dinosaurs was fluffy and soft.  

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