I think someone may have posted this already, but in case not: https://www.smithsonianmag.com/smart-news/t-rex-skin-was-not...

"T. Rex Was Likely Covered in Scales, Not Feathers"

What I don't understand is how something the size of T rex doesn't just die from heat shock whenever it breaks into a sprint. I vaguely recall reading somewhere that one of the dangers facing beached whales is that they start to overheat rapidly. Did big dinosaurs just live in cooler environments? Do they have better ways to dissipate heat? Did they like dipping in lakes and ponds? I'm sure someone would have asked these questions already, but no idea what current thinking in the field is...