Khankhuuluu is the latest Tyrannosaur relative to be identified by paleontologists, recognized from long-recovered fossils and now believed to be the closest known ancestor of the iconic large predators.
The discovery was led by University of Calgary PhD student Jared Voris and UC researcher Dr. Darla Zelenitsky, who headed an international team. Their work fills in critical gaps in the evolutionary and migratory history of the Tyrannosaur family.
Khankhuuluu
The dinosaur’s name—Khankhuuluu—is derived from a Mongolian phrase meaning “Prince of Dragons,” echoing the linguistic connection to Tyrannosaurus rex, which translates to “The Tyrant Lizard King.” Khankhuuluu lived approximately 86 million years ago, during a period following the extinction of earlier large predators. It was a fast, medium-sized carnivore weighing around 1,600 pounds—only a third to half the size of a fully grown T. rex.
“This new species provides us the window into the ascent stage of Tyrannosaur evolution; right when they’re transitioning from small predators to their apex predator form,” says lead author Jared Voris.
Evolving the Tyrant Lizard King
Khankhuuluu represents an important evolutionary stage in the lineage that led to T. rex, though it lacked many traits defining its famous descendant. It had the early development of horns—features that would later become prominent in species like Albertosaurus and Gorgosaurus, used for mating displays or intimidation.
Unlike T. rex, it had a long, shallow skull that lacked the powerful bite seen in later Tyrannosaurs. Instead, Khankhuuluu likely relied on speed and agility to hunt, behaving more like a modern coyote than a bone-crushing apex predator.
Identifying the Tyrannosaur Ancestor
The fossils used in this study were not recently excavated but had remained unexamined in Mongolia’s Institute of Paleontology for about 50 years. Altangerel Perle, now a paleontologist at the National University of Mongolia, first uncovered the remains in the 1970s while working in the Bayanshiree Formation in southern Mongolia. At the time, the fossils were thought to belong to Alectrosaurus, a dinosaur already known from China.
It wasn’t until 2023 that Voris examined the fossils and identified unique characteristics that set Khankhuuluu apart as a new species, helping to clarify key points in the evolutionary tree of Tyrannosaurs.
“Khankhuuluu, or a closely related species, would have immigrated to North America from Asia around 85 million years ago,” explains Zelenitsky, a paleontologist and associate professor in the Department of Earth, Energy and Environment. “Our study provides solid evidence that large Tyrannosaurs first evolved in North America as a result of this immigration event.”
Path of the Tyrannosaur
The Dragon Prince, or a close relative, likely crossed a land bridge into North America before giving rise to the Tyrannosaur line. The lineage remained in North America for millions of years before fossil evidence suggests a return migration to Asia.
Fundamentally, the discovery of Khankhuuluu—the last known Tyrannosaur ancestor to inhabit Asia—has reshaped our understanding of Tyrannosaur migration patterns.
Overall, it now appears that movement between Asia and North America was more structured and less sporadic than previously thought.
The paper “A New Mongolian Tyrannosauroid and the Evolution of Eutyrannosauria” appeared on June 11, 2025, in Nature.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.