Paleontology News
Image showing Dinosaurs from the end Cretaceous of North America, including T rex: Image Credit-Pedro Salas and Sergey Krasovskiy (CC BY 4.0)
Tracing Tyrannosaurus rex to Its Asian Ancestors
New research suggests Tyrannosaurus rex evolved in North America from Asian ancestors, while megaraptors were globally distributed predators whose size and success were shaped by climate change. Read the news story below:
Summary Points
Tyrannosaurus rex holotype (CM9380).
T. rex evolved in North America but likely descended from Asian ancestors.
These dinosaurs likely crossed the Bering land bridge over 70 million years ago.
Tyrannosaurids and megaraptors grew rapidly in size as global temperatures cooled.
Megaraptors were more globally distributed than previously thought, originating in Asia.
Both groups replaced older giant predators after an extinction event.
The study emphasizes how climate change and continental drift shaped dinosaur evolution.
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T. rex’s Asian Roots Revealed: Dinosaurs Crossed Land Bridge to Rule North America
This article is based on a new release by University of Leicester - May 6, 2025, and the Open Access (CC BY 4.0) Journal Article (Cassius Morrison et al, 2025) from Royal Society Open Science.
A groundbreaking new study led by researchers at University College London suggests that Tyrannosaurus rex, though it evolved in North America, likely descended from ancestors that migrated from Asia over 70 million years ago. These prehistoric predators are believed to have crossed the Bering land bridge from modern-day Siberia to Alaska, establishing a powerful lineage that would later include one of history's most iconic dinosaurs. This finding supports earlier research connecting T. rex more closely to Asian tyrannosaurs like Tarbosaurus than to North American species such as Daspletosaurus.
The researchers used advanced modeling that combined fossil data, evolutionary trees, geography, and paleoclimate to track the movements of tyrannosaurids and their lesser-known cousins, the megaraptors. Interestingly, both groups experienced a surge in size around the same time the Earth began cooling after a peak in temperatures 92 million years ago. This timing suggests these predators were better adapted to cooler climates - possibly thanks to feathers or warm-blooded traits - compared to their rivals.
Megaraptors, in contrast to T. rex, were leaner with massive arms and long claws, and the new research suggests they were more globally widespread than previously thought. While their fossils are mostly known from the Southern Hemisphere, the models indicate that megaraptors originated in Asia and expanded through Europe, Africa, and Gondwana, potentially thriving in places where fossils have yet to be found. Their evolution may have diverged due to different prey and hunting strategies.
The extinction of carcharodontosaurids, previously dominant meat-eaters, may have paved the way for both tyrannosaurids and megaraptors to evolve into apex predators. With the ecological top spots vacant, both groups grew in size dramatically - T. rex eventually reaching up to nine tons, and megaraptors stretching over 10 meters in length. Each adapted to their respective ecosystems, from T. rex hunting ceratopsians in Laramidia to megaraptors preying on sauropods in southern continents.
The findings not only shed light on the transcontinental journey of T. rex's ancestors, but also highlight how climate, extinction events, and continental drift shaped the evolution of large predatory dinosaurs. While tyrannosaurs ruled Asia and North America, megaraptors adapted to become dominant hunters in Patagonia and Australia. The study opens the door for future discoveries - perhaps even fossils of T. rex's ancestors still waiting to be found in Asia.
The end Cretaceous Northern Hemisphere fauna was dominated by Tyrannosaurids (such as Tyrannosaurus rex), hadrosaurs and ceratopsian ornithischian dinosaurs. (CC BY 4.0)
Journal Article:
Morrison Cassius, Scherer Charlie Roger, O’Callaghan Ezekiel V., Layton Collin, Boisvert Colin, Rolando Mauro Aranciaga, Durrant Leroy, Salas Pedro, Allain Steven J. R. and Gascoigne Samuel J. L. (2025) Rise of the king: Gondwanan origins and evolution of megaraptoran dinosaurs. Royal Society Open Science 12242238 https://doi.org/10.1098/rsos.242238.
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