Tyrannosaurus rex scavenged on Edmontosaurus annectens carcasses in the Late Cretaceous, according to a study published in PLoS ONE. Researchers from Loma Linda University identified specific tooth traces on 12 out of 3,013 fossilized bones from a Wyoming bonebed, concluding the lack of bone healing indicates scavenging rather than active predation.
Precision Mapping of T-Rex Feeding Habits in the Lance Formation
Paleontologists examined a massive collection of bones excavated between 1997 and 2017 near Hanson Ranch Station in northeastern Wyoming. The site, part of the Lance Formation, yielded 3,013 bones primarily belonging to the duck-billed hadrosaur Edmontosaurus annectens.
According to Dr. Bethania Siviero and her colleagues, identifying tooth marks is notoriously difficult. Many bone depressions are incorrectly labeled as bite marks when they are actually natural anatomical features. To solve this, the team used CT scans to verify the lesions.
Only 12 bones—including ribs, vertebrae, a radius, and an ulna—were confirmed to have genuine tooth traces. Four of these displayed patterns matching two known ichnospecies: Knethichnus parallelum and Linichnus serratus. By matching the spacing of these marks to the dental structure of predators in that ecosystem, the researchers identified Tyrannosaurus rex as the most likely culprit.
Did you know? Only 12 of the 3,013 bones in this specific Wyoming bonebed showed genuine tooth marks, highlighting how rare physical evidence of feeding is in the fossil record.
Scavenging vs. Predation: The Evidence in the Bone
Because the bitten bones showed no signs of healing, Siviero and her team concluded the T. rex fed on the animals around the time of death or afterward.
This suggests a scavenging behavior.
Comparative Analysis of Tooth Trace Identification
| Feature | Previous Criteria | Siviero et al. Approach |
|---|---|---|
| Verification | Visual inspection of depressions | CT scans and anatomical review |
| Context | Often ignored or ambiguous | Integrated with ecosystem data |
| Result | Potential for misleading behavior data | Refined standards for “tooth traces” |
Establishing New Standards for Paleontology
The research aims to fix a recurring problem in the field. Dr. Siviero noted that “mistaken identification of tooth traces has led to misleading interpretations of animal behavior.” By critically reviewing previous criteria, the team is pushing for a more rigorous standard in how paleontologists identify perforations in fossil bone.
This shift toward high-resolution imaging and stricter anatomical verification helps prevent “parsimonious etiologies”—simpler, non-predatory explanations—from being overlooked in favor of more exciting, but incorrect, predation theories.
Frequently Asked Questions
Did T-Rex only scavenge?
The study focuses on this specific bonebed where evidence points to scavenging. It does not claim T. rex never hunted active prey.
What is the Lance Formation?
It is a geological formation in northeastern Wyoming.
How do CT scans help identify bite marks?
CT scans allow researchers to see the internal structure of the bone and determine if a hole is a natural growth or a mechanical perforation caused by a tooth.
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