One day about 72 to 66 million years ago, a plant-eating dinosaur became Tyrannosaurus rexfood. Several fossilized bones discovered in Wyoming over several digs between 1997 and 2017 feature tooth marks that were likely the result of a big bite by a T. rex. The fossils are detailed in a study published today in the journal PLOS One, and are helping paleontologists piece together an extinct ecosystem.
“The study of tooth marks on fossil bones is important because it provides valuable insights into animal behavior and interactions between species,” the study’s authors wrote in a joint statement.
In the study, authors Bethania C. T. Siviero, Elizabeth Rega, Matthew A. McLain, Leonard R. Brand, David Nelsen, and Art V. Chadwick examined over 3,000 bones found in northeastern Wyoming. They date back to about 72 to 66 million years ago, during the late Cretaceous period. Most of the bones were from Edmontosaurus annectens, a large, duck-billed herbivorous dinosaur that lived in present-day western North America.
Out of 3,013 bones in the study, only 12 had traces of teeth. Four had distinct tooth mark patterns, and based on the spacing and shape of these marks, the team believes that they are the result of a T. rex bite. Some of the other tooth traces may have been created by other meat-eating dinosaurs and crocodilians.
Importantly, most of the bones with tooth marks do not have any evidence of healing. This means that the marks were most likely made around or after the animals’ died. The animals may have been hunted while they were alive, or a larger carnivore may have scavenged their carcasses after death. The remaining bones were then buried and fossilized over tens of millions of years.
To help future researchers, the study also includes a tooth mark guide that describes and identifies several types of punctures, holes, and other marks on fossils that appear to be tooth marks.
In fossils, tooth marks often look like punctures or furrows. However, similar marks can form on bones for several other reasons, including joint disease, or erosion after the animal died. In order to study prehistoric ecology and animal behavior using bite marks, scientists must ensure that what they’re looking at really are bite marks. Laying out a set of criteria for identifying tooth marks in fossil bones could be a vital paleontological research tool.
“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 authors concluded.
Who knows what other evidence of dinosaur meals may be lurking deep underneath the ground just waiting to be dug up. However, that duck-billed dinosaur might grumble over just how valuable its death was 72 million years ago.
