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They have found what looks like a direct ancestor of Tyrannosaurus rex, and it throws doubt on everything they thought they knew about T. rex evolution. The theory had been that something of similar size, but clumsier, had evolved the fierce jaws and small forelimbs.
Raptorex kriegsteini lived about 60 million years before T. rex. And it looks like a miniature T. rex. Same general shape, complete with the tiny forelimbs that were assumed to be a late-evolved characteristic. It has the same jaw and teeth. According to the abstract:
Raptorex kriegsteini lived about 60 million years before T. rex. And it looks like a miniature T. rex. Same general shape, complete with the tiny forelimbs that were assumed to be a late-evolved characteristic. It has the same jaw and teeth. According to the abstract:
We show that their most conspicuous functional specializations—a proportionately large skull, incisiform premaxillary teeth, expanded jaw-closing musculature, diminutive forelimb, and a hindlimb with cursorial proportions—were present in a new small-bodied, basal tyrannosauroid from Lower Cretaceous rocks in northeastern China. These specializations, scaled up in Late Cretaceous tyrannosaurids with body masses approaching 100 times greater, drove the most dominant radiation of macropredators of the Mesozoic.