What does the geological setting of *Xiongguanlong* in Early Cretaceous Gansu suggest about tyrannosauroid evolution?

That defining characteristics of the group, like skull elongation and arm reduction, were diversifying across Asian faunas much earlier than previously estimated.

The presence and morphology of *Xiongguanlong* in Early Cretaceous Western China provide critical geographic context that shifts understanding of tyrannosauroid origins. Since many famous, large tyrannosaurs originate later from North America and Mongolia, finding a specialized, advanced basal form like *Xiongguanlong* in Gansu suggests that the key evolutionary trends—such as the gradual process of skull elongation and arm reduction—were actively underway and driving morphological change within East Asian ecosystems during the Aptian-Albian stages, rather than simply resulting from migration or inheriting traits developed elsewhere.