US EditionScientists Confirm Nanotyrannus as Distinct Species
The study analyzed growth rings and anatomy of fossils from Montana's Hell Creek Formation, confirming two Nanotyrannus species as distinct from Tyrannosaurus rex adults.
- In October 2025, Zanno and Napoli published in Nature that the Dueling Dinosaurs' small predator is a fully grown Nanotyrannus lancensis, not a juvenile Tyrannosaurus rex, and they named a second species, Nanotyrannus lethaeus.
- The Dueling Dinosaurs specimen preserves forearm and tail elements, and growth rings and spinal fusion indicate about 20 years and skeletal maturity.
- Comparison of 200 tyrannosauroid fossils revealed that Nanotyrannus has larger forelimbs, hands, finger bones and claws, distinct skull nerve and sinus patterns, and fewer tail vertebrae than T. rex.
- The finding forces a re-examination of decades of T. rex research, as it used Nanotyrannus material to model growth and behavior, and confirms higher predator diversity in the last million years before the asteroid impact.
- Phylogenetic analysis indicates that Nanotyrannus lies outside the core Tyrannosauridae lineage, and the paper also suggests reclassifying Dryptosaurus and Appalachiosaurus, implying multiple tyrannosaur species coexisted in the late Cretaceous last million years.
146 Articles
146 Articles
“Dueling Dinosaurs” Fossil Solves One of Paleontology’s Biggest Debates
Scientists have proven Nanotyrannus was its own species, reshaping what we know about the predators that lived alongside T. rex. What if our understanding of T. rex growth has been wrong all along? A newly analyzed tyrannosaur skeleton has brought one of paleontology’s longest-running controversies to an end: the question of whether Nanotyrannus represents a [...]
The Dueling Dinosaurs Mystery May Have Been Solved — The Baby T. rex Was Instead a Nanotyrannus
Learn how the legendary “Dueling Dinosaurs” fossil revealed that a supposed teenage Tyrannosaurus rex was actually a full-grown Nanotyrannus — changing what we know about tyrant evolution.
Palaeontology breakthrough as scientists reveal new T-Rex cousin species
A new palaeontological breakthrough based on analysis of the “Dueling Dinosaurs” fossil has revealed that the T. rex had a smaller cousin species.The “Dueling Dinosaurs” fossil was unearthed in 2006 and is considered one of the most dramatic discoveries in palaeontology.The fossil features a Triceratops, a tanky horned dinosaur, and a lean, agile carnivorous dinosaur, believed to be a T. rex, engaged in combat.Researchers have long debated wheth…
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