Paleontologists examined an exceptionally well-preserved, nearly somatically mature tyrannosaurus skeleton from the Hell Creek Formation in Montana. Their results show that the specimen shares similarities with the holotype specimen Nanotyrantand demonstrate that this line is different from Tyrannosaur.
“This Fossil Changes Decades” Tyrannosaurus rex research on its head,” said Dr. Lindsay Zanno, a researcher at North Carolina State University and the North Carolina Museum of Natural Sciences.
Using growth rings, spinal fusion data and developmental anatomy, the researchers demonstrated that the new specimen was about 20 years old and physically mature.
Its skeletal features, including larger forelimbs, more teeth, fewer caudal vertebrae, and distinct distribution of cranial nerves, are features recorded early in development and are biologically incompatible with Tyrannosaurus rex.
“For Nanotyrant be underage Tyrannosaurus rexit would have to challenge everything we know about vertebrate growth. It's not just unlikely, it's impossible,” said Dr. James Napoli, a researcher at Stony Brook University.
For many years, paleontologists have used Nanotyrant fossils for modeling Tyrannosaur growth and behavior.
This new data shows that these studies were based on two completely different animals – and that multiple species of tyrannosaurs inhabited the same ecosystems in the last million years before the asteroid impact.
As part of their research, Dr. Zanno and Dr. Napoli examined more than 200 tyrannosaur fossils.
They discovered one skeleton that was previously believed to be that of a teenager. Tyrannosaurus rexslightly different from the previously described species Nanotyranus lanceolatawhich is part of the famous “Dueling Dinosaurs” fossil.
The authors concluded that the sample represents a new Nanotyrant view and named it Nanotyrannus letaus.
Validity confirmation Nanotyrant means that the diversity of predators in the last million years of the Cretaceous period was much higher than previously thought, and hints that other small-bodied dinosaur species may also have been victims of misidentification.
“This discovery paints a richer, more competitive picture of the last days of the dinosaurs,” Dr Zanno said.
“Possessing enormous size, powerful bite force and stereoscopic vision, Tyrannosaurus rex was a formidable predator, but did not reign supreme.”
“It was rushing nearby Nanotyrant – a slimmer, faster and more agile hunter.”
conclusions appear in the magazine today Nature.
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L.E. Zanno and J.G. Napoli. Nanotyrant And Tyrannosaur coexisted at the end of the Cretaceous. Naturepublished online October 30, 2025; doi: 10.1038/s41586-025-09801-6
