This is a very cool fossil, a tiny T. rex cousin called Raptorex. Well, tiny is relative — it was still as big as a human being — but it has the same proportions, the oversized fanged head, the tiny forelimbs, etc., as it’s later relative, T. rex. It’s simply adorable, in a viciously evil predatory sort of way. Apparently the tyrannosaur body plan was successful at different scales.