Science Mystery of Tyrannosaurus rex solved
A thorough analysis of dinosaur bones clears up a long-standing misconception about Tyrannosaurus rex. Until now, fossils of Nanotyrannus lancensis were considered by many scientists to be a juvenile form of the T-Rex.
31.10.2025, 05:31
SDA
Now a US team presents an overwhelming list of evidence in the scientific journal "Nature" as to why this is extremely unlikely. Lindsay Zanno and James Napoli from the North Carolina Museum of Natural Sciences in Raleigh (North Carolina) also came across a previously unknown dinosaur species while examining hundreds of fossils.
For Zanno, the publication is also the admission of an error: she was part of the team that published a study in the journal "Science Advances" in 2020, in which the fossils of the species Nanotyrannus lancensis were assigned to the T-Rex. One reason for their doubts about the thesis could have been a study published in the journal "Fossil Studies" in January 2024: In it, other researchers described the fossil of an actual juvenile T-Rex, among other things, and in this way showed that the Nanotyrannus fossils have nothing to do with the T-Rex.
The reference specimen of Nanotyrannus lancensis was already described in 1946 and called Gorgosaurus lancensis at the time. It was not until further investigations in 1988 that it was renamed Nanotyrannus lancensis. However, there was controversy among experts as to whether it was actually a separate species, as the few existing fossils were very similar to T. rex. In 2013, the fossils of a Nanotyrannus lancensis (predatory dinosaur) and a Triceratops (herbivore) were offered as "dueling dinosaurs" in a controversial auction - scientists called for them to be transferred to a museum.
Result turns decades of research on T. rex on its head
Close examination of the largely complete predatory dinosaur fossil has now led Zanno and Napoli to the realization that N. lancensis is a separate species. "This fossil doesn't just end the debate - it turns decades of research on T. rex on its head," Zanno is quoted as saying in a statement from North Carolina State University in Raleigh, where she is a professor. Because scientists used Nanotyrannus fossils for years to reconstruct the growth of T. rex, much of the supposed knowledge about T. rex coming of age is probably inaccurate.
"For Nanotyrannus to have been a young Tyrannosaurus rex, it would have to contradict everything we know about vertebrate growth. That's not just unlikely - it's impossible," said Napoli. For example, the Nanotyrannus has longer arms in relation to its body than the T-rex. The Nanotyrannus has 35 tail vertebrae, while the T-Rex has at least 40. The Nanotyrannus also has more teeth than the T-Rex. In addition, the pattern of nerve tracts in the skull differs significantly between the species. Last but not least, the growth rings in the bones of the Nanotyrannus became narrower and narrower towards the outside, which indicates a fully-grown animal.
Still unknown dinosaur species identified
During the examination of more than 200 Tyrannosaurus and Nanotyrannus fossils, the researchers discovered that a fossil with the technical designation BMRP 2002.4.1, which was previously categorized as T-Rex or N. lancensis, represents a previously unknown species: Nanotyrannus lethaeus. The species name is named after the river Lethe in the underworld of Greek mythology. While N. lancensis probably weighed around 700 kilograms, N. lethaeus probably weighed more than 1200 kilograms. Other physical characteristics also point to a separate species.
"This discovery paints a more comprehensive and meaningful picture of the end of the dinosaurs," explained Zanno. With its enormous size, powerful bite and spatial vision, the T. rex was a fearsome hunter - but not alone in the field, Zanno emphasized. According to the latest findings, Nanotyrannus was a slimmer, faster and more agile hunter than the T-rex.
