Tyrannosaurus rex likely migrated from Asia to North America approximately 70 million years ago, according to new research. This discovery sheds light on the ancient origins and global journey of one of history’s most iconic predators. Illustration by Pedro Salas and Sergey Krasovskiy.
The legendary Tyrannosaurus rex, the undisputed king of the dinosaurs, likely didn't just appear in North America. A groundbreaking new study suggests its direct ancestors made a remarkable journey across a land bridge from Asia, igniting fresh debate among paleontologists about the origins of this iconic predator.
Led by Cassius Morrison, a bright doctoral student in paleontology at University College London (UCL), the research team employed sophisticated mathematical modeling to trace the lineage of T. rex. Their compelling conclusion: the precursors to the mighty tyrant king likely traversed the ancient Bering Strait, connecting modern-day Siberia and Alaska, approximately 70 million years ago.
This intriguing finding aligns with previous research hinting at a closer evolutionary relationship between T. rex and Tarbosaurus, a formidable Asian carnivore, compared to other apex predators that roamed North America, such as the fearsome Daspletosaurus, Morrison explained.
Imagine a vastly different landscape during that era. Morrison described to CNN a region cloaked in temperate rainforests, boasting a climate reminiscent of present-day British Columbia. Within this lush environment, tyrannosaurids, the ancestors of T. rex, would have been relatively scarce compared to the herbivorous dinosaurs they hunted – a dynamic mirroring modern apex predators like lions.
"And because they are fewer, there are also fewer chances for them to then be preserved in the fossil record," Morrison astutely pointed out.
Faced with this inherent scarcity of direct fossil evidence, Morrison and his fellow researchers cleverly employed mathematical models. These models ingeniously integrate existing fossil data, the established T. rex family tree, and crucial climatic and environmental conditions to paint a more complete picture.
Crucially, the modeling also intelligently accounts for gaps in the fossil record. This foresight ensures that the model can be dynamically updated and refined as future paleontological discoveries come to light. In fact, Morrison highlighted that their study suggests that undiscovered fossils of these pivotal T. rex ancestors may still lie hidden within the ancient landscapes of Asia.
The Puzzle of Gigantism: Why Did T. Rex Become So Massive?
The team's insightful analysis didn't stop at geographical origins. They also unearthed a fascinating link between global temperature fluctuations and the dramatic size increase observed in tyrannosaurids like T. rex. Their findings indicate that this rapid growth spurt coincided with a period of declining global temperatures. This suggests that these colossal dinosaurs may have possessed physiological adaptations, such as feathers or a degree of warm-bloodedness, that allowed them to thrive in cooler climates.
Furthermore, the researchers propose that the extinction of another group of giant meat-eating dinosaurs, the carcharodontosaurids, around 90 million years ago played a crucial role. This extinction event likely created an "ecological vacuum at the top of the food chain," as stated in a UCL news release.
This newfound ecological opportunity paved the way for tyrannosaurs to evolve into the colossal giants that dominated the Late Cretaceous period. By the time the age of dinosaurs drew to a close, T. rex could have reached a staggering weight of up to 9 metric tons – a mass comparable to a very large African elephant or even a light tank, according to the release.
Study co-author Charlie Scherer, a master's graduate in Earth sciences and future doctoral student at UCL, emphasized the significance of their findings. He stated that their work "has shined a light on how the largest tyrannosaurs appeared in North and South America during the Cretaceous Period and how and why they grew so large by the end of the age of dinosaurs."
"They likely grew to such gigantic sizes to replace the equally giant carcharodontosaurid theropods that went extinct about 90 million years ago," Scherer elaborated. "This extinction likely removed the ecological barrier that prevented tyrannosaurs from growing to such sizes."
Expert Perspective: Climate Played a Key Role
Steve Brusatte, a distinguished paleontologist at the University of Edinburgh in Scotland, who was not involved in the study, lauded the research as "fine scholarly work." He noted that the study "forensically tracks tyrannosaurs and other meat-eating dinosaurs over time, and compares their evolution with changes in climate."
Brusatte offered a compelling perspective: "Even the very largest and most dominant dinosaurs were affected by the weather. It seems like tyrannosaurs were able to get big multiple times independently, when cooler climates promoted increases in size."
He concluded with an insightful remark: "It was easier to be big when temperatures were cool. The kings of the dinosaurs were not predestined to rule, but were helped along by the climate."
This fascinating study, published in the esteemed journal Royal Society Open Science, provides valuable new insights into the origins and evolutionary journey of the mighty Tyrannosaurus rex, highlighting the significant role of both geographical connections and environmental factors in shaping the reign of this iconic dinosaur.