Overview
- Researchers used growth rings, spinal fusion and developmentally fixed anatomy to show the tyrannosaur was about 20 years old and fully grown.
- Comparisons across more than 200 tyrannosaur fossils supported recognition of Nanotyrannus lancensis and led to the naming of a second species, N. lethaeus.
- Key differences from T. rex include larger forelimbs, higher tooth counts, fewer tail vertebrae and distinct cranial nerve and sinus patterns that do not align with T. rex growth.
- The study concludes Nanotyrannus coexisted with T. rex in late‑Cretaceous Hell Creek ecosystems, indicating greater predator diversity than previously assumed.
- The specimen—part of Montana’s 2006 “Dueling Dinosaurs” discovery now at the North Carolina Museum of Natural Sciences—prompts calls to reexamine decades of T. rex growth and biomechanics research.