“Sue: The T. Rex Experience” is on display through May 12, 2024 at the Memphis Museum of Science and History. The focal point of the exhibit is a replica of Sue, the largest and most complete specimen of a Tyrannosaurus rex ever discovered.
Calgary, Canada – A newly identified species of dinosaur, Khankhuuluu mongoliensis — or “dragon prince of Mongolia” — may hold the key to understanding how tyrannosaurs like Tyrannosaurus rex rose to the top of the prehistoric food chain. Described in a study published Wednesday in Nature, the discovery of this modestly sized predator provides a long-missing link in the evolutionary story of one of history’s most fearsome lineages.
Weighing approximately 1,700 pounds and measuring 13 feet in length, K. mongoliensis lacked the colossal bulk of later tyrannosaurs but shared their defining traits: bipedal stance, sharp teeth, and small arms. Yet its smaller head and longer arms hint at a transitional phase — a form caught between the earlier, more agile tyrannosauroids and the lumbering giants that dominated the late Cretaceous.
The fossils that led to the identification were first unearthed in Mongolia’s Gobi Desert during expeditions in the 1970s and initially misclassified as belonging to Alectrosaurus. But when Jared Voris, a Ph.D. candidate from the University of Calgary, reexamined the bones decades later, he realized they told a different story.
“I realized it was something completely different than anything we’d ever seen,” Voris said. The fossils exhibited characteristics that set them apart from known genera, indicating they were a distinct, older ancestor of apex predators, such as T. rex and Tarbosaurus.
The dating of the fossils — to approximately 86 million years ago — is critical. It places K. mongoliensis nearly 20 million years before T. rex, suggesting tyrannosaurs didn’t start as giants. Instead, they evolved through a series of migrations and ecological pressures.
Using comparisons across 12 tyrannosaur species, researchers reconstructed the family tree and migration patterns of these predators. They found that around 85 million years ago, a species related to K. mongoliensis likely crossed from Asia into North America via a land bridge, where the Bering Strait lies today, giving rise to the North American tyrannosaurs. Later, another wave of migration back into Asia gave rise to giant species like Tarbosaurus and smaller, long-snouted forms, such as “Pinocchio rex.”
The last known migration, approximately 68 million years ago, may have brought an Asian tyrannosaur back to North America, leading to the rise of T. rex.
Though small by tyrannosaur standards, the dragon prince stands tall as a crucial figure in the story of life on Earth.
