Mystery of T. Rex’s Debated North American Origins Finally Solved

Paleontologists are divided at the beginning of certainly one of our favourite dinosaurs, Tyrannosaurus rex. Some say its ancestry is firmly rooted in North America. Others don’t seem to be satisfied.

An world workforce, led by way of paleoecologist Cassius Morrison from University College London, now proposes the horrible lizard’s ‘grandparents’ can have as a substitute migrated to North America from Asia around the Bering Strait.

“Dozens of T. rex fossils have been unearthed in North America but our findings indicate that the fossils of T. rex‘s direct ancestor may lie undiscovered still in Asia,” Morrison says.

“This is in line with past research finding that the T. rex was more closely related to Asian cousins such as the Tarbosaurus than to North American relatives such as Daspletosaurus.”

In 2024 a systematic workforce reported {that a} fossil present in New Mexico, from the T. rex relative Tyrannosaurus mcraeensis, predated its extra well-known counterpart by way of round 6 million years. They took this to imply that large-bodied tyrannosaurs had a North American beginning.

Morrison’s workforce argues this conclusion – and the age estimated for T. mcraeensis – is unreliable, because of the shortage of specimens and present technological barriers.

Their strategies for tracing Tyrannosaur circle of relatives historical past as a substitute concerned modeling in line with the fossil report (and its gaps), the dinosaur evolutionary tree and knowledge at the local weather and geography of the time. It specifically unearths how tyrannosaurids and megaraptors can have moved around the continents.

Based on those fashions, the workforce argues that despite the fact that the T. rex genus most likely arose in western North America – or somewhat the prehistoric continent Laramidia, because the land mass of the time is understood – its direct ancestors most likely migrated throughout from Asia.

“The genus Tyrannosaurus originated in Laramidia from an ancestrally Asian taxon that emigrated to North America during the Late Campanian – Early Maastrichtian,” the authors write.

This is not a brand new proposition: even the tiniest of T. rex‘s family members left fossils that recommend a Beringian land bridge migration.

Megaraptors, they discovered, most likely emerged in Asia round 120 million years in the past, ahead of dispersing to Europe and the southern ‘supercontinent’ Gondwana. But no megaraptor fossils were present in Europe or Africa – a minimum of, now not but.

“At the beginning of their evolutionary history, around 120 million years ago, megaraptors were part of a widespread and diverse dinosaur fauna,” explains paleontologist Mauro Aranciaga Rolando, from the Bernardino Rivadavia Natural Sciences Argentine Museum.

“As the Cretaceous period progressed and the continents that once formed Gondwana began to drift apart, these predators became increasingly specialized. While in regions like Asia megaraptors were eventually replaced by tyrannosaurs, in areas such as Australia and Patagonia they evolved to become apex predators, dominating their ecosystems.”

As the arena’s local weather turned into cooler round 92 million years in the past, each megaraptors and tyrannosaurids reached gigantic sizes. But the workforce discovered no direct correlation between local weather and gigantism in those dinosaurs. Instead, they will were higher tailored to the chilly, permitting them to take over the newly vacant apex predator area of interest of their environments.

“They likely grew to such gigantic sizes to replace the equally giant carcharodontosaurid theropods that went extinct about 90 million years ago,” says UCL paleontologist Charlie Scherer. “This extinction likely removed the ecological barrier that prevented tyrannosaurs from growing to such sizes.”

The analysis is revealed in Royal Society Open Science.