A 75-million-year-old fossilized foot bone from Montana shows bite marks from a smaller tyrannosaur feeding on a much larger relative. Researchers used 3D scans to document this evidence of scavenging behavior. The finding, published this year, highlights opportunistic feeding among these ancient predators.
Josephine Nielsen, a Master's student in geoscience at Aarhus University, led the analysis of a tyrannosaur metatarsal fossil discovered in Montana's Judith River Formation. The bone, now at the Badlands Dinosaur Museum in Dickinson, North Dakota, bears 16 distinct bite marks. Nielsen applied high-resolution 3D scanning and the CM classification system to confirm the marks came from a smaller tyrannosaur's teeth on the larger, several-ton specimen, likely 10-12 meters long in life. The marks show no signs of healing and appear on a low-meat area, indicating scavenging late in decay after soft tissues were gone. “I have analyzed the depth, angle, and placement of the marks in a virtual 3D environment and can document that these bite marks did not occur by chance. They are precise impressions from the teeth of a smaller tyrannosaur that fed on a much larger relative,” Nielsen said. She worked with digital models and a 3D print due to shipping risks for the original. The study, published in Evolving Earth, was supported by paleontologist Taia Wyenberg-Henzler and curator Denver Fowler. Nielsen connected with them during a 2024 Montana excavation camp. “The bone shows no signs of healing after the smaller dinosaur bites into it. Since the marks are located on the foot, where there is very little meat, it suggests that the dinosaur was 'cleaning up' and eating the last remains of an old carcass,” she explained. This research demonstrates how digital tools reveal precise details of dinosaur behavior, establishing a standardized way to interpret bite marks.