How does the skull morphology of *Xiongguanlong* contrast with derived Late Cretaceous tyrannosaurids?

It features a distinctive long and narrow skull with an elongate preorbital region accounting for more than two-thirds of its length.

A key feature distinguishing *Xiongguanlong* from later, more derived tyrannosaurids is its cranial architecture. Unlike the powerful, deep, and boxier skulls associated with later forms that specialized in immense biting force—the hallmark of apex predators like *T. rex*—*Xiongguanlong* retained a remarkably long and narrow skull. Its preorbital region, the area in front of the eye socket, constituted over two-thirds of the total skull length, a morphology that provided a specialized muzzle reminiscent of the contemporary genus *Alioramus* rather than the robust crushing jaws of its successors.