Although its ancestors probably did have feathers, as recent research has suggested, a new study published this week in the journal Biology Letters has concluded that the Tyrannosaurus rex did not, and was in fact covered in scales similar to those found on modern-day lizards.

In the new study, Phil R. Bell, a paleontologist from the University of New England in Australia, and his colleagues analyzed skin impressions from a T.rex skeleton found in Montana, as well as from four related species (Albertosaurus, Daspletosaurus, Gorgosaurus and Tarbosaurus) late in the tyrannosaur’s history, according to BBC News and the Washington Post.

While recent studies had found that two tyrannosauroids that preceded the T. rex by around 50 million years (Dilong and Yutyrannus) were covered in feathers, the new analysis of the T. rex itself revealed that the creature’s abdomen, chest, pelvis, neck, and tail were covered exclusively in scales. If it had feathers, they were limited to its back or spines, the authors said.

“With all the hype about feathered theropods, it’s easy to forget that actually, most dinosaurs had scaly, reptilian-like skin,” Bell told the Post via email. However, he noted, the new study “shows without question that T. rex had scaly skin.” The reasons for this trait remain a mystery, although size may have played a role.

“Big animals have trouble shedding excess heat, so being covered in feathers is not a good idea unless you live somewhere cold,” he explained. However, while Dilong was much smaller than the T. rex, Yutyrannus was closer to the size of the larger dinosaur, lived in similar climates and still had feathers. “So what’s the reason for this difference? We really don’t know.”

Some researchers dispute the research’s conclusion, however

The debate over whether T. rex was covered in scales or feathers can be traced back to a lack of fossil evidence, according to BBC News. One of the reason tyrannosaur skin is rare, Bell told the Post, is that paleontologists long preferred to break through it to get to the creature’s bones.

Bell and his colleagues reported that skin patches from the neck, pelvis, and tail of the Montana-based T. rex, along with similar findings on its relatives, indicate that their outer covering (fossil integument) “possessed scaly reptilian-like skin.” Not all researchers are convinced, however.

University of London paleontologist David Hone, who was not involved in the research, told the Post that the research “doesn’t rule out feathers on… tyrannosaurs, but does suggest they lacked a full coat of feathers.” University of Edinburgh paleontologist Dr. Steve Brusatte agreed.

“I don’t think we can assume that T. rex lacked feathers just because some fossil skeletons have skin impressions that are scaly,” Dr. Brusatte told BBC News. “It takes inconceivable good luck to preserve feathers in fossils. Just because we don’t see them doesn’t mean they weren’t there. So I don’t think we need to throw out the image of a big fluffy T. rex quite yet.”

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Image credit: Peter Larson, Black Hills Institute

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