T. rex was likely responsible for some tooth marks on fossil bones from Cretaceous-era Wyoming
New research helps researchers confirm if marks on fossils are indeed bite marks
image:
Tooth trace types on neural spine fragments. A) Punctures on opposing surfaces in neural spine HRS01295. The image only depicts one of the punctures indicated by the white box. An arrow indicates the location of the other puncture not visible in the image. B) A magnified view of the puncture within the white box area on Fig 4A. C) A view of the puncture opposing the puncture on Fig 4B and indicated by arrow on Fig 4A. D) Neural spine fragment HRS03650 with a score indicated by an arrow. E) A view of the opposing surface from HRS03650 (Fig 4D) shows a deep and curved score with associated tooth trace ichnotaxon Linichnus serratus.
view moreCredit: C. T. Siviero et al., 2026, PLOS One, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
A collection of fossilized dinosaur bones from Wyoming feature tooth marks that provide evidence that some bites were likely created by Tyrannosaurus rex, according to a study published July 15, 2026 in the open access journal PLOS One by Bethania C. T. Siviero from Loma Linda University, USA, and colleagues.
Tooth marks on fossilized bones offer scientists unique insights into ecosystems and animal behavior millions of years ago. This study describes and identifies several types of punctures, holes, and other marks on fossils that appear to be tooth marks. The researchers developed a guide, based on previously published research and their new findings, for how to interpret tooth traces on fossils.
The research team examined over 3,000 bones from northeastern Wyoming from the late Cretaceous period, about 72 - 66 million years ago. Most of the bones were from Edmontosaurus annectens, a large, duck-billed herbivorous dinosaur.
Just 12 of the bones had tooth traces. Four of those bones had distinct tooth mark patterns, and based on the shape and spacing of these marks, the researchers believe they came from T. rex. Some of the other tooth traces may have been created by other contemporaneous carnivores, including other dinosaurs and crocodilians.
Most of the bones with tooth marks show no evidence of any healing around the marks, meaning that these marks were probably made around or after the animals’ deaths. This, along with previous research on bones from this site, indicates that not only may some of the animals have been predated, but also that their carcasses may have been exposed to the elements and scavenged, before eventually being buried and fossilized.
Tooth marks in fossils often look like punctures or furrows, but similar marks can form on bones for a variety of other reasons, such joint disease, or erosion after the animal has died. If researchers want to study prehistoric ecology and animal behavior using bite marks, they need to ensure that these really are bite marks. By laying out a set of criteria for identifying tooth marks in fossil bones, this study helps to hone a vital paleontological research tool.
The authors add: “Correctly identifying bone depressions and perforations is important because not all of these features are tooth marks. Some are caused by diseases, while others result from post-mortem processes such as insect activity or other processes due to bone exposure. Distinguishing between these different types of bone modifications is essential, as they can provide valuable information about an animal's condition before death as well as the processes that affected its remains after death.”
“The study of tooth marks on fossil bones is important because it provides valuable insights into animal behavior and interactions between species.”
Tooth trace types on rib specimens. A) Prominent furrow tooth trace on rib fragment HRS09477. B) Two puncture traces on rib fragment HRS09477 indicated by arrows on the opposing side of a furrow on Fig 3A. C) Magnified image of the puncture on HRS09477 indicated by arrow 2 on Fig 3B, indicating the pull and drag from the bite. D) Rib fragment HRS03161 with puncture and associated drag from the bite. E) Rib fragment HRS09551 with parallel scores. F) Rib HRS03387 with prominent scores and associated tooth trace ichnotaxon Knethichnus parallelum. G) Magnification of area indicated by the white box featuring prominent and detailed parallel Knethichnus parallelum traces. H) Rib HRS09954 with a long score trace indicated by the arrow.
Credit
C. T. Siviero et al., 2026, PLOS One, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
Excavation of dinosaur fossil bones from an Edmontosaurus annectens monodominant bonebed of the Upper Cretaceous Lance Formation, Wyoming, USA.
Credit
Bethania C.T. Siviero, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
In your coverage, please use this URL to provide access to the freely available article in PLOS One: https://plos.io/4eVZgJ7
Citation: C. T. Siviero B, Rega E, McLain MA, Brand LR, Nelsen D, Chadwick AV (2026) Identification of tooth traces from a Cretaceous (Maastrichtian) Edmontosaurus annectens bonebed in the Lance Formation, Wyoming, U.S.A. PLoS One 21(7): e0351939. https://doi.org/10.1371/journal.pone.0351939
Author countries: USA.
Funding: Internal fundings from Loma Linda University.
Journal
PLOS One
Method of Research
Observational study
Subject of Research
Animals
Article Title
Identification of tooth traces from a Cretaceous (Maastrichtian) Edmontosaurus annectens bonebed in the Lance Formation, Wyoming, U.S.A.
Article Publication Date
15-Jul-2026
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