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What evidence shows that Dilong had protofeathers?
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tyrannosaur
The fossilized remains of Sue, the most complete Tyrannosaurus rex skeleton in the world, on display at the Field Museum of Natural History, Chicago.
The evidence for protofeathers in Dilong comes from the discovery of fossil specimens in the Yixian Formation of western Liaoning province, China, which include direct impressions of these structures.1
These protofeathers consisted of branched filaments that reached lengths of up to 2 cm (0.8 inch). Rather than resembling the contour feathers seen on modern birds, these filaments appeared more like a coat of hair. The presence of these structures in Dilong provided the first evidence that tyrannosaurs, like many other coelurosaurian theropods, were feathered. This discovery suggests that such filaments likely evolved initially for insulation rather than for flight.12