Where Did the T. rex Come From? Paleontologists Think They've Finally Figured It Out

Yahoo

10-05-2025

Fossils of the T. rex, tyrant lizard and queen of the dinosaurs, are found exclusively in North America. Strangely, they have more in common with other large theropod dinosaurs in Asia than they do with their predatory peers in the United States and Canada.
A new study published in the journal Royal Society Open Science may have finally figured out why that is. Analyzing the fossils and evolutionary history of T. rex and related dinosaur groups, paleontologists suggest that T. rex (prehistoric star of Universal's Jurassic Park and Jurassic World films) originated in North America but descended from ancestors which migrated from Asia about 70 million years ago.
Paleontologists debate over whether the direct ancestors of Tyrannosaurs came from North America or Asia. A new study led by University College London Ph.D student Cassius Morrison may have answered the question once and for all.
'Our modelling suggests the 'grandparents' of T. rex likely came to North America from Asia, crossing the Bering Strait between what is now Siberia and Alaska,' explained researcher Cassius Morrison, via the Natural History Museum, London. 'This is in line with past research finding that the T. rex was more closely related to its Asian cousins than to North American relatives such as Daspletosaurus. Our findings indicate that, while dozens of T. rex fossils have been unearthed in North America, the fossils of its direct ancestor may lie undiscovered still in Asia.'
The world 90 million years ago looked a little bit different. If you go back about 250 million years ago, all the world's land masses were gathered together in the supercontinent Pangaea. It began to break up about 200 million years ago, separating into the ancient continents of Laurasia in the north and Gondwanaland in the south. By the time we reached the Cretaceous (144 - 66 million years ago), the modern continents had separated but were still squished together tightly. North America was separated into two continents, Laramidia in the west and Appalachia in the east, separated by the Western Interior Seaway. Travel between the land masses was a little easier then than it is now.
Those long-extinct ancestors of Tyrannosaurs were significantly smaller than their more famous descendants. Some were roughly equivalent to a medium-sized dog while others were small enough to sit comfortably on your shoulders. They first started getting big about 90 million years ago, when the large-statured carcharodontosaurid theropods went extinct. Exploiting a vacant niche, Tyrannosaurs evolved from their diminutive ancestors to become apex predators of the Late Cretaceous.
Around the same time the carcharodontosaurids were going extinct, the planet was going through a period of rapid cooling. The world reached a peak in global temperatures known as the Cretaceous Thermal Maximum about 92 million years ago, then temperatures dropped. Tyrannosaurids and a related group of large predators known as the megaraptors survived because they were better equipped for colder temperatures and grew to gigantic sizes to fill the empty niche.
'Our findings have shined a light on how the largest tyrannosaurs appeared in North and South America during the Cretaceous and how and why they grew so large by the end of the age of dinosaurs,' said Charlie Scherer, also from University College London, via Sci News.
However Rexy got here, we're just glad she did, cause she makes for great entertainment! Catch Jurassic World Dominion, , and for Jurassic World Rebirth, in theaters July 2.