(Read the paper here, FREE ACCESS:  (https://www.sciencedirect.com/science/article/pii/S2950117226000038)

Key Findings

• A metatarsal (foot bone) from a large adult tyrannosaur has tooth marks where it had been bitten by another carnivore
• Lack of healing shows that the tooth marks were made when the tyrannosaur was already dead
• Spacing of the tooth marks suggest they were made by a much smaller, juvenile tyrannosaur
• This is the first example of a juvenile tyrannosaur cannibalizing a much larger adult
   

Background
Tyrannosaurs were the largest land carnivores ever to have lived, and dominated the dinosaur ecosystem of North America in the Late Cretaceous Period. We are used to seeing images of tyrannosaurs standing triumphantly above their vanquished prey, gorging on a bloody meal. However, a recently discovered fossil from Badlands Dinosaur Museum in North Dakota flips this view around. 

New discovery
In a new paper released today, Josephine Nielsen and coauthors describe a metatarsal (foot bone) from an adult tyrannosaur which has multiple tooth marks cut into the end of the bone. This time, the giant tyrannosaur was a meal for someone else! 

The tooth marks are nearly parallel to each other forming a number of sets made by multiple teeth during the same biting action. Spacing between the toothmarks represents the spacing between the teeth themselves, allowing us to calculate the size of the carnivore feeding on the carcass. Intriguingly, it appears that the large adult tyrannosaur was being nibbled on by a much smaller tyrannosaur, probably a juvenile.

There is no sign of healing around the marks showing that the adult tyrannosaur was already dead when it was fed upon. Furthermore, there would not have been much meat on the feet. This suggests that the small tyrannosaur fed on the large tyrannosaur’s carcass after it had been lying on the land surface for some time, during which most of the best meat had already been eaten by other scavengers.

Conclusions
Although fairly rare, cannibalism is documented in modern carnivores, and evidence for cannibalism within tyrannosaurs has been noted before. The new specimen not only adds another specimen for scientists to study, but it is the first example with a reversed body size discrepancy between the large-bodied carcass and small-bodied scavenger.

Where are the specimens from?
The specimen (BDM 124) was discovered in 2012 by fossil collectors Brent and Rod Olson on private land in central Montana which contains exposures of the Judith River Formation. In 2023, it was donated to the public repository at Badlands Dinosaur Museum, Dickinson Museum Center, Dickinson, North Dakota.

Points of contact
Josephine Nielsen: josephine.nielsen [at] post.au.dk (josephine[dot]nielsen[at]post[dot]au[dot]dk)
Denver Fowler: denver.fowler [at] dickinsongov.com (denver[dot]fowler[at]dickinsongov[dot]com)
 

About the researchers
Josephine Nielsen is a researcher from Aarhus University, Denmark, and was a 2024 Badlands Dinosaur Museum field team member
Dr. Denver Fowler is curator of the Badlands Dinosaur Museum in Dickinson, North Dakota, USA
Taia Wyenberg-Henzler is a tooth mark specialist and PhD candidate at the University of Edmonton, Alberta, Canada, and was a 2025 Badlands Dinosaur Museum field team member
Dr. Aase Roland Jacobsen is a curator at Science Museums, Aarhus University, Denmark, tooth mark specialist and a former associated researcher at The Royal Tyrrell Museum of Paleontology.
Dr. Christof Pearce is a professor at Aarhus University, Denmark

Reference: Nielsen J; Fowler DW; Wyenberg-Henzler, T;  Jacobsen AR, & Pearce, C. (2026) Investigating size-asymmetric feeding among tyrannosaurids using tooth marks on a metatarsal from the Judith River Formation, Montana, USA. Evolving Earth. https://www.sciencedirect.com/science/article/pii/S2950117226000038 (final version published online Jan. 31st 2026)