A new Nature study by Lindsay Zanno and James Napoli proposes that the Burpee Museum’s famed tyrannosaur "Jane" represents a distinct species, Nanotyrannus lethaeus, rather than a juvenile T. rex. The authors reexamined hundreds of tyrannosaur fossils and report growth patterns, bone microstructure and proportions inconsistent with juvenile T. rex. Nanotyrannus is described as a smaller (~18 ft), more agile predator with proportionally longer legs and stronger forelimbs. The paper has prompted renewed discussion and further study of other key specimens to resolve tyrannosaur diversity at the end of the Cretaceous.
Jane May Not Be T. rex: Study Names Rockford Fossil Nanotyrannus lethaeus
A new Nature study by Lindsay Zanno and James Napoli proposes that the Burpee Museum’s famed tyrannosaur "Jane" represents a distinct species, Nanotyrannus lethaeus, rather than a juvenile T. rex. The authors reexamined hundreds of tyrannosaur fossils and report growth patterns, bone microstructure and proportions inconsistent with juvenile T. rex. Nanotyrannus is described as a smaller (~18 ft), more agile predator with proportionally longer legs and stronger forelimbs. The paper has prompted renewed discussion and further study of other key specimens to resolve tyrannosaur diversity at the end of the Cretaceous.
13:26, 04.11.2025Science
Rockford’s famous fossil "Jane" may be a distinct species, not a juvenile T. rex
Jane, the well-known tyrannosaur specimen on display at the Burpee Museum of Natural History, may not be a juvenile Tyrannosaurus rex after all. A new paper in Nature by Lindsay Zanno (North Carolina Museum of Natural Sciences) and James Napoli (Stony Brook University) argues that Jane represents a separate species, which the authors name Nanotyrannus lethaeus.
The study reexamined hundreds of tyrannosaur fossils, including Jane, and reports distinctive growth trajectories, bone microstructures and skeletal proportions in smaller tyrannosaur specimens that the authors say are inconsistent with them being juvenile T. rex. According to the paper, Nanotyrannus appears to have been a more lightly built, fleet-footed predator — roughly 18 feet long — with proportionally longer legs and relatively stronger forelimbs than the giant, heavyset T. rex, which could reach about 40 feet.
"We’ve always known Jane was special," said Anne Weerda, executive director of the Burpee Museum, emphasizing that whether Jane is an unusually preserved juvenile or the only known specimen of a new species, she remains scientifically important and a source of local pride.
The fossil was recovered from Montana’s Hell Creek Formation and brought to Rockford 23 years ago. For decades, paleontologists have debated whether smaller tyrannosaur skeletons represent juvenile growth stages of T. rex or a separate taxon. Zanno and Napoli’s analysis adds new data to that debate and, the announcement reports, has persuaded a number of previously skeptical researchers to reassess their positions after examining the specimen and associated data.
Researchers describe Nanotyrannus as adapted for speed and agility, likely relying on pursuit or ambush tactics, whereas adult T. rex were built for enormous size and bite force. The authors and participating institutions stress that ongoing study of other key specimens — including the famed "Dueling Dinosaurs" at the North Carolina Museum of Natural Sciences — will help clarify tyrannosaur diversity and life history across the end of the Cretaceous.
"Jane is an extraordinary specimen—not just scientifically, but as a point of pride for Rockford," said Joshua Mathews, head of paleontology at the Burpee Museum. He noted the community’s role in discovery, excavation and preparation, and that Jane has remained central to paleontological research for more than two decades.
While the new study is influential, taxonomic revision in paleontology often involves continued scrutiny, additional specimens and further analyses. For now, Jane will remain a focal point in efforts to understand tyrannosaur growth, behavior and diversity in the Late Cretaceous.
This article was adapted from reporting by Abreanna Blose (ablose@gannett.com) and includes material from a community announcement by the Burpee Museum of Natural History.