Scientists have uncovered a previously unknown dinosaur species, Khankhuuluu mongoliensis, dating back 86 million years, that fills a critical gap in the early fossil record of tyrannosaurs and reveals how these iconic predators evolved into massive apex hunters. Discovered in Mongolia’s Gobi Desert in the early 1970s, the two partial skeletons of Khankhuuluu provide vital clues about the transitional phase between small early tyrannosauroids and the colossal late Cretaceous giants like Tyrannosaurus rex.
Measuring about 13 feet (4 meters) long, Khankhuuluu was significantly smaller than its later relatives, illustrating that tyrannosaurs remained modest in size for much of their early history. This discovery helps scientists understand the gradual evolutionary steps that led to the rise of enormous tyrannosaurs dominating ecosystems toward the end of the Cretaceous period.
Importantly, the research suggests that around 85 million years ago, Khankhuuluu or a close relative migrated from Asia to North America via a land bridge, giving rise to the first true tyrannosaurs that ruled North America until their extinction 66 million years ago. Subsequently, tyrannosaurs migrated back to Asia about 78 million years ago, revealing complex migration patterns that fueled their diversification.
This breakthrough has prompted a revision of the tyrannosaur family tree, highlighting how early tyrannosaurs developed advanced senses and cognitive skills before evolving into giant apex predators. Khankhuuluu mongoliensis fills a long-standing gap in the fossil record and offers a clearer understanding of tyrannosaur origins, rewriting the history of one of the most famous dinosaur lineages and illuminating the path to their reign as the "kings of the dinosaurs."
