Scientists have long been intrigued by the origins of a dinosaur unearthed in the 1940s, questioning whether it was a juvenile Tyrannosaurus rex or an entirely different species. Initial findings relied solely on a tyrannosaur skull, leading to challenges in determining the age of the specimen.
The debate intensified with the introduction of another skull and skeleton, known as “Jane,” but the controversy remained unresolved. Recent research, however, has provided new insights that may clarify the situation.
A research team has announced the discovery of a complete skeleton, originally found in Montana in 2006, which they assert belongs to a distinct dinosaur species rather than a young T. rex. This revelation, detailed in a study published in the journal Nature, is said to “rewrite decades of research” concerning one of Earth”s most renowned predators, according to study co-author Lindsay Zanno from the North Carolina Museum of Natural Sciences and North Carolina State University.
The team analyzed growth rings present in the bones from the Hell Creek Formation in Montana, suggesting that the newly identified dinosaur was an adult and approximately half the size of a mature T. rex. By comparing growth rates to those of other reptiles, such as crocodiles, researchers concluded that the significant differences in skull structure, nerve patterns, and sinuses between this dinosaur and an adult T. rex were unlikely to arise merely from the process of puberty.
The findings point towards a dinosaur closely related to Nanotyrannus lancensis, a lesser-known relative of T. rex. Holly Woodward, a fossil bone specialist at Oklahoma State University who was not involved in the study, noted that there is now “more support and evidence than ever” for the existence of this relative.
Despite this, she remains skeptical about other skeletons like Jane potentially being distinct species. Other paleontologists, including Thomas Carr from Carthage College, also caution against drawing definitive conclusions. Although the new skeleton is confirmed as an adult, it could represent a sister species rather than a distant relative of T. rex. Carr remarked, “I don”t think this study settles everything,” highlighting that the similarities in skull shape between T. rex and the specimens in question complicate the issue.
Understanding this case of mistaken identity is crucial for comprehending the growth patterns of T. rex, as emphasized by study co-author James Napoli from Stony Brook University. An additional area of inquiry is whether T. rex was the primary predator at the end of the dinosaur era, approximately 67 million years ago, or if a smaller yet formidable predator also inhabited the landscape.
The newly identified skeleton, referred to as the “Dueling Dinosaurs,” was found entangled with a Triceratops skeleton and is currently displayed at the North Carolina Museum of Natural Sciences.
For further details, refer to the study “Nanotyrannus and Tyrannosaurus coexisted at the close of the Cretaceous,” published in Nature (2025).
