Wyoming’s fresh T. rex bones show exactly how the predator tore its prey apart

A dense jumble of dinosaur bones in northeastern Wyoming has given paleontologists something they rarely obtain: physical traces of a Tyrannosaurus rex feeding on its food. Among thousands of fossils excavated from a single bonebed, a small number carry tooth marks that match the serrated teeth of the great predator, preserving the instant its jaws met bone tens of millions of years ago.

Direct evidence of what T. rex actually did with its teeth is surprisingly scarce, because bite marks seldom survive and are easy to confuse with damage from other animals or from the sediment that entombed the bones. A newly published analysis is notable both for what it found and for how carefully it ruled out the alternatives, offering a grounded look at the animal’s feeding behavior rather than a reconstruction based on jaw mechanics alone.

A Wyoming bonebed packed with duck-billed dinosaurs

The fossils come from the Lance Formation of northeastern Wyoming, a rock layer laid down at the very end of the Cretaceous, roughly 66 million years ago. The bonebed is dominated by Edmontosaurus annectens, a large, plant-eating, duck-billed dinosaur that lived alongside T. rex in the final chapter before the mass extinction. The study, published in the open-access journal PLOS One in July 2026, describes an examination of more than three thousand individual bones pulled from that one site, an unusually large sample that let the researchers treat the search for tooth marks as a rigorous statistical exercise rather than a hunt for a single dramatic specimen.

Assemblages like this, where many animals of the same species accumulated in one place, are valuable precisely because they capture an ecosystem rather than an isolated skeleton. Any predator or scavenger working through such a deposit would leave traces spread across many bones, if those traces survived at all.

Twelve marked bones out of more than three thousand

The most striking result is how rare the marks turned out to be. Of the 3,013 bones examined, only thirteen showed surface features that looked like tooth traces, and closer inspection reclassified one of those as damage from a different cause entirely. That left twelve bones with genuine tooth marks, and four of them carried the distinctive patterns the team attributed to Tyrannosaurus rex. The scarcity is itself informative: it suggests that feeding traces from the era’s apex predator were the exception rather than the rule, and it cautions against reading dramatic behavior into every scratch on a fossil.

The low count also underscores why careful methodology matters. With so few marked bones in such a large sample, a single misidentification would meaningfully distort any conclusion about how often the predator fed on these carcasses.

What the scored bone reveals about the bite

The marks the team linked to T. rex are not random gouges but recognizable trace types with formal names. The bones carry traces classified as Knethichnus parallelum and Linichnus serratus, the kinds of marks left when a serrated tooth is dragged across a bone surface. Knethichnus parallelum in particular records a row of parallel grooves scored into the bone as the fine serrations along a tooth’s edge rake past, in effect a fingerprint of a bladed, steak-knife tooth pulling through flesh and scraping the bone beneath. Reading those patterns lets paleontologists reconstruct the motion of the jaw as it stripped soft tissue from the skeleton, turning static fossils into a record of the feeding action itself.

That is the sense in which the Wyoming bones show how the predator worked at a carcass: the geometry, depth and spacing of the scores line up with the size and serration of tyrannosaur teeth, distinguishing them from the punctures or crushing damage other animals leave behind.

Ruling out the impostors

Part of the study’s value lies in what it excluded. One bone that initially looked bitten was reassigned to a different origin once its perforations were examined closely, a reminder that not every hole or groove in a fossil is a dinosaur bite. To sort real traces from lookalikes, the researchers weighed the shape, depth, orientation and spacing of each mark and compared them against the expected signature of tyrannosaur teeth, and in the process they refined the broader criteria that scientists use to identify tooth traces on fossil bone at all. The result is a more conservative and repeatable standard, one that other researchers can apply to bonebeds elsewhere.

Scavenger, hunter, or both

What the marks cannot settle is whether the T. rex killed the Edmontosaurus or simply fed on animals that were already dead. Tooth traces record feeding, not the manner of death, so a bitten bone is equally consistent with an active kill and with scavenging a carcass. That ambiguity fits a long-running debate about the lifestyle of T. rex, which most paleontologists now regard as an opportunistic feeder that both hunted and scavenged depending on what was available. The Wyoming bones do not crown the animal as a pure predator or a pure scavenger, but they do add hard physical evidence that it fed on the herds of duck-billed dinosaurs that shared its world, one dragged tooth at a time.

This article was produced with AI assistance and reviewed by Morning Overview editors.

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