Fossilized dinosaur bones found in Wyoming contain tooth marks that researchers say were likely made by Tyrannosaurus rex, according to a study published July 15, 2026 in PLOS One.
The work was led by Bethania C. T. Siviero of Loma Linda University and focused on more than 3,000 bones collected in northeastern Wyoming. Those fossils date to the late Cretaceous period, about 72 to 66 million years ago.
Most of the bones belonged to Edmontosaurus annectens, a large plant-eating dinosaur with a duck-shaped bill. Only 12 of the bones showed possible tooth traces, and four had patterns the researchers said matched the shape and spacing of T. rex teeth.
According to the study, the team concluded that T. rex was the most likely source of those marks, though other damaged bones may have been bitten by other predators or scavengers such as carnivorous dinosaurs and crocodilians. Most of the marked bones showed no signs of healing, suggesting the bites happened near the time of death or after the animals had died.
The researchers say identifying real tooth marks is difficult because disease, insects, weathering and erosion can all leave similar features on bone. They say their new guide for interpreting possible tooth marks should help paleontologists better use fossil damage to study prehistoric behavior and ecological relationships.
