“This fossil turns years of Tyrannosaurus rex research study on its head,”stated Dr. Lindsay Zanno, a scientist at North Carolina State University and the North Carolina Museum of Natural Sciences.

Utilizing development rings, spine combination information and developmental anatomy, the scientists showed that the brand-new specimen was around 20 years old and physically fully grown.

Its skeletal functions– consisting of bigger forelimbs, more teeth, less tail vertebrae, and unique skull nerve patterns– are functions repaired early in advancement and biologically incompatible with Tyrannosaurus rex

“For Nanotyrannus to be a juvenile Tyrannosaurus rexit would require to defy whatever we understand about vertebrate development. It’s not simply not likely– it’s difficult,” stated Dr. James Napoli, a scientist at Stony Brook University.

For many years, paleontologists have actually utilized Nanotyrannus fossils to design Tyrannosaurus development and habits.

This brand-new proof exposes that those research studies were based upon 2 totally various animals– which several tyrannosaur types lived in the exact same communities in the last million years before the asteroid effect.

As part of their research study, Dr. Zanno and Dr. Napoli took a look at over 200 tyrannosaur fossils.

They found that a person skeleton, previously believed to represent a teenage Tyrannosaurus rexwas a little various than the previously-described types Nanotyrannus lancensiswhich becomes part of the well-known Dueling Dinosaurs fossil.

The authors concluded that the specimen represents a brand-new Nanotyrannus types and called it Nanotyrannus lethaeus

Verification of the credibility of Nanotyrannus suggests that predator variety in the last million years of the Cretaceous duration was much greater than formerly believed, and tips that other small-bodied dinosaur types may likewise be victims of incorrect identity.

“This discovery paints a richer, more competitive image of the last days of the dinosaurs,” Dr. Zanno stated.

“With huge size, an effective bite force and stereoscopic vision, Tyrannosaurus rex was a powerful predator, however it did not rule uncontested.”

“Darting along with was Nanotyrannus — a leaner, swifter and more nimble hunter.”

The findings appear today in the journal Nature

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L.E. Zanno & & J.G. Napoli. Nanotyrannus and Tyrannosaurus existed together at the close of the Cretaceous. Naturereleased online October 30, 2025; doi: 10.1038/ s41586-025-09801-6