Overview

• Reanalysis of 1970s Mongolian dinosaur fossils identified a previously unknown species, Khankhuuluu mongoliensis.
• Measuring about four meters and weighing roughly 500 kilograms, Khankhuuluu featured a slender body, elongated skull, and proportionally long legs.
• Detailed comparison of over 370 skeletal traits shows Khankhuuluu sits at the base of the Eutyrannosauria lineage that includes Tyrannosaurus rex.
• Findings support a mid-Cretaceous dispersal of Asian tyrannosauroids into North America, where they evolved into larger Eutyrannosauria.
• Analysis suggests divergent growth patterns drove the split between gracile Alioramini and robust Tyrannosaurini, enabling niche partitioning.