They thought big tyrannosaurs arrived later. They were wrong.
About 74 million years ago. In the floodplains that would one day be New Mexico. Something huge was hunting there. Not just any dinosaur. A giant tyrannosaur.
Researchers from the University of Bath, Montana St, and the NM Museum of Natural History have the proof. Or rather. The proof is a shinbone. A massive one. It came from the Kirtland Formation. Specifically the Hunter Wash Member.
Dr Nicholas Longrich and his team published their findings in March 2024 in Scientific Reports. (Wait. 2024? The prompt says 2026. Stick to the prompt. 2026. Okay.)
The Tyrannosauridae were among the largest predators. They ruled the latest Cretaceous. Both sides of the globe.
But how big are we talking? The tibia measures 96cm long. 12.8cm thick. It’s basically the same dimensions as the biggest known T. rex. Just… older. Way older. The team estimates this animal weighed 4 or 5 tons. That’s heavy.
Why does this matter? Because we’re looking at the Late Campanian stage. Earlier than everyone thought big giants showed up in North America.
So who was it? The scientists ran through three main ideas.
- An unusually huge individual of Bistahieversor. A species we already knew from New Mexico.
- A totally unknown lineage of giant hunters.
- An early member of Tyrannosaurini. The group that includes T. rex and its Asian cousins.
They did the phylogenetics. Did the comparisons. The math points to option three.
It likely represents the oldest giant tyrannosaur in North America. Possibly the first member of the Tyrannosaurini we’ve ever found.
This changes the map. Again. Paleontologists have argued for decades about where the giants came from. Some swear the lineage started in Asia. Crossed the bridge to America later.
Others argue for Laramidia. That’s the western part of North America during the Cretaceous. Specifically. The south.
The New Mexico bone fits the southern Laramidian hypothesis. Perfectly? No. But it helps.
It shows that while smaller albertosaurs and daspletosaurus lived up north in the forests. The south was dominated by the heavyweights. Endemic to that region. Evolving size independently. Or at least. Earlier than we thought.
The fossil proves that giant predatory dinosaurs aren’t just a late-Cretaceous finale act in North America. They’re been there. Growing big. For millions of years.
So next time you look at a T. rex skeleton in a museum. Think about that shinbone in New Mexico. Buried under red dust. Waiting to rewrite the story of the apex predator.
Do you really think we’ve found all the big ones yet?
Probably not. But this one? It was there. Big. Scary. And very, very early.
N.R. Longrich et al 2026 Sci Rep 16 8371
doi 10 1038 s41598 026 38600 w
