A 2025 paper by Lindsay Zanno and James Napoli concluded that some bones from the 'Dueling Dinosaurs' specimen represent a fully grown individual of Nanotyrannus lancensis rather than a juvenile Tyrannosaurus rex.
October 30, 2025
high
temporal
Taxonomic reinterpretation of bones from the well-known 'Dueling Dinosaurs' fossil assemblage.
Specimens identified as Nanotyrannus have been reported to show, relative to Tyrannosaurus rex, proportionally longer forearms, fewer tail vertebrae, and a greater number of teeth.
high
morphological
Reported anatomical differences cited in comparative studies of small-bodied tyrannosaur specimens versus T. rex.
Tyrannosaurus rex existed approximately 67 million years ago during the late Cretaceous period.
high
temporal
Tyrannosaurus rex is commonly placed near the end of the Cretaceous in biostratigraphic and geochronological frameworks.
Nanotyrannus lancensis is described as a small-bodied, agile tyrannosauroid with relatively long legs and proportionally larger forelimbs compared with Tyrannosaurus rex.
high
taxonomic
Morphological descriptions of small tyrannosauroid taxa emphasize adaptations for speed and agility versus the larger, more robust form of T. rex.