Tyrannosaurus rex has a yawn. All right, so it looks like it could be roaring instead, but I had a yawn in mind when I made this.
I’ve read that a close cousin of T. rex, the Tarbosaurus from late Cretaceous Asia, has yielded evidence for a dewlap-like fold of skin under its throat, so I decided to give one to my rex too. However, I do think the current trend of assuming all dinosaurs in any evolutionary grouping had a certain trait only because one member of that group has been found with that trait is overrated. That’s like assuming all big cats must have manes because lions do. If multiple tyrannosaurids were to show evidence of dewlaps, I might accept this was ancestral to the group. But right now, for all we know that dewlap could be unique to Tarbosaurus and its most immediate ancestors.