A new study led by researchers at University College London (UCL) has revealed that the mighty Tyrannosaurus rex, one of history’s most famous predators, likely had its roots in Asia.
According to the study, T. rex’s direct ancestor crossed over from Asia to North America around 70 million years ago, using a land bridge that once connected Siberia and Alaska.
This discovery challenges previous beliefs that T. rex originated entirely in North America.
The research, published in Royal Society Open Science, also showed that the massive growth in size of T. rex and its relatives, the tyrannosaurids, coincided with a major global cooling event around 92 million years ago.
As temperatures dropped, these giant predators thrived, likely because they were better suited to cooler climates. Lead author Cassius Morrison, a Ph.D. student at UCL Earth Sciences, explained that the geographic origin of T. rex has been a heated topic among paleontologists for years.
Their findings suggest that T. rex’s “grandparents” came from Asia, which aligns with earlier research indicating that T. rex shared more similarities with Asian dinosaurs like Tarbosaurus than with its North American cousins like Daspletosaurus.
While many T. rex fossils have been uncovered in North America, Morrison and his team believe that fossils of its direct ancestors might still be hidden in Asia, waiting to be discovered.
The study also disputes a previous claim that a T. rex relative called Tyrannosaurus mcraeensis, found in New Mexico, predates T. rex by three to five million years. The team argued that the dating of the T. mcraeensis fossil is unreliable.
The researchers used advanced modeling techniques to trace the movements of tyrannosaurids and another mysterious group of giant predators called megaraptors. These models were built using fossil records, evolutionary trees, and climate data from the time.
The study found that megaraptors, which had slender heads and long, powerful claws, originated in Asia about 120 million years ago before spreading to Europe and the massive southern continent of Gondwana, which included present-day Africa, South America, and Antarctica.
Although megaraptors are less well-known than T. rex, the study suggests they were more widespread than previously thought.
Their fossils have been found mostly in South America, but the researchers believe they may have also roamed Europe and Africa, even though no fossils have been discovered there yet. Unlike T. rex, which used its powerful bite to take down large prey like Triceratops and Edmontosaurus, megaraptors may have hunted juvenile sauropods using their long, sharp claws.
The study also explains why both tyrannosaurids and megaraptors grew so large during the same period. Around 92 million years ago, global temperatures began to cool, and another group of giant predators called carcharodontosaurids went extinct.
With these competitors out of the way, tyrannosaurs quickly filled the gap at the top of the food chain. By the end of the dinosaur age, T. rex weighed as much as nine metric tons—similar to an African elephant or even a light tank—while megaraptors reached lengths of up to 10 meters.
The findings help paint a clearer picture of how the largest predators of the Cretaceous period spread across the world and grew to such colossal sizes. Co-author Charlie Scherer, an Earth Sciences graduate and soon-to-be Ph.D. student at UCL, explained that the extinction of rival predators likely gave tyrannosaurs the space they needed to evolve into the giants we know today.
Dr. Mauro Aranciaga Rolando, another co-author from Argentina’s Bernardino Rivadavia Natural Sciences Museum, added that megaraptors followed a different evolutionary path. While they eventually disappeared in Asia, they thrived in places like Australia and Patagonia, where they became dominant predators.
As the continents drifted apart, megaraptors evolved to adapt to their unique environments, continuing their reign in isolated ecosystems long after their Asian relatives vanished.
This new study not only challenges long-held beliefs about T. rex’s origins but also reshapes our understanding of how giant predators spread and evolved across ancient Earth.
