[my_pointy_head_is_sharp]

They are birds same with the T-Rex

From Wikipedia:

T-Rex was among the last non-avian dinosaurs to exist prior to the Cretaceous–Tertiary extinction event.

Skin and feathers - skin impressions from large tyrannosaurid specimens show mosaic scales

[Steve Van Doorn]

It has been in debate for a long time if they were birds or not. I tend to believe they are based on their legs.