Why did T. rex have feathers?

Why did T. rex have feathers? Paleontologists think feathers may have first evolved to keep dinosaurs warm. But while a young T. rex probably had a thin coat of downy feathers, an adult T. rex would not have needed feathers to stay warm.

Paleontologists think feathers may have first evolved to keep dinosaurs warm. But while a young T. rex probably had a thin coat of downy feathers, an adult T. rex would not have needed feathers to stay warm.
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