A tiny, earlier cousin of Tyrannosaurus rex sported at least a partial coat of hairlike feathers, scientists reported today. Although predicted by several paleontologists, the discovery marks the first time featherlike structures have been directly observed on a tyrannosaurid.

According to Norell, the American Museum of Natural History paleontologist, large adult tyrannosaurs like T. rex probably lacked primitive feathers, an indication that the hairlike structures evolved to insulate warm-blooded dinosaurs rather than to enable flight.

"It's doubtful a 40-foot-long tyrannosaur was covered with this stuff, if we are right that [the feathers] were needed for insulation. As the dinosaurs get bigger, they need to dump heat, not hold onto it," Norell said. Xu added that even large dinosaurs like T. rex may have had feathers when they were young. "They are not likely to be completely featherless animals for [their] whole life," he said."

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