A 66-million-year-old Edmontosaurus skull, cataloged as MOR 1627, preserves an embedded tyrannosaurid tooth and matching bite marks on its face, with no sign of healing around the wound. The specimen was discovered in 2005 in Montana’s Hell Creek Formation on land managed by the Bureau of Land Management’s Miles City Field Office. CT scans performed at Bozeman Health Deaconess Hospital confirmed that the tooth’s orientation and placement are consistent with a face-to-face strike, meaning the tyrannosaur bit directly into the front of the hadrosaur’s skull. The absence of bone remodeling around the embedded tooth indicates the bite occurred at or very near the moment of death.
Why a fatal face bite changes what paleontologists know about T. rex hunting
Most evidence of tyrannosaur predation comes from bones that show healed injuries, suggesting the prey survived the attack. A separate, well-known specimen documents a T. rex tooth crown lodged in a hadrosaurid tail vertebra surrounded by regrown bone, proving that particular animal lived long enough for its skeleton to repair itself. MOR 1627 tells the opposite story. Because no healing occurred, the bite either killed the Edmontosaurus outright or landed on an animal already dying. That distinction matters for reconstructing how large theropods attacked living prey rather than simply scavenging carcasses.
The location of the bite is equally telling. Tooth marks on tails and limbs are relatively common in the Late Cretaceous fossil record. A bite aimed squarely at the face of another large dinosaur implies a different kind of encounter, one where predator and prey were oriented toward each other. Researchers analyzing MOR 1627 interpret the tooth orientation and placement as consistent with a direct, frontal strike rather than an opportunistic bite taken from behind or from the side of a fleeing animal.
That scenario supports the idea that tyrannosaurids sometimes targeted the head and neck, where a single well-placed bite could disable or kill large prey quickly. A frontal attack is riskier for the predator, exposing it to blows from the victim’s limbs or tail, but it also offers the chance to crush the skull, damage the braincase, or sever major blood vessels. In MOR 1627, the tooth’s position in the facial bones suggests the tyrannosaur’s jaws closed with enough force to penetrate dense bone and then snap the tooth crown, leaving it locked in place.
One hypothesis worth examining is whether the frequency of unhealed facial bites in Hell Creek hadrosaurs could reflect seasonal resource stress. If food or water became scarce during dry periods, hadrosaurs and tyrannosaurs would have concentrated around the same shrinking resources, increasing the odds of direct, aggressive encounters. The current fossil record, however, does not contain enough specimens with unhealed facial injuries to test that idea statistically. MOR 1627 is a single data point, and without dozens of comparable skulls from the same formation, any correlation between bite frequency and environmental conditions remains speculative.
The specimen also feeds into the long-running debate over whether large tyrannosaurids were primarily hunters or scavengers. Clear-cut evidence of active predation is rare, because paleontologists must show that a bite occurred while the victim was still alive or freshly killed. In this case, the face-to-face orientation, the embedded tooth, and the lack of healing combine to make a strong case that the tyrannosaur engaged a living Edmontosaurus at close range. While MOR 1627 cannot settle the hunter-versus-scavenger question on its own, it adds a vivid example of lethal, directed aggression to the growing catalog of tyrannosaur feeding traces.
CT scans and comparative studies anchor the MOR 1627 findings
The peer-reviewed study published in PeerJ documents the embedded tyrannosaurid tooth and associated tooth marks on the articulated Edmontosaurus skull. The researchers used the CT imaging performed at Bozeman Health Deaconess Hospital to map the tooth’s position within the bone and assess fracture patterns in the surrounding skull material. The tooth’s angle and depth, combined with the lack of any bone remodeling, allowed the team to distinguish this bite from post-mortem feeding, where a scavenger gnaws on remains that are already decomposing.
Those CT slices show how the tooth crown wedges between bony struts in the snout, with microfractures radiating outward from the point of impact. In living bone, such trauma would trigger a cascade of biological responses, including new bone growth and smoothing of fracture edges. None of those features are present in MOR 1627. Instead, the fracture surfaces remain sharp and unmodified, consistent with a wound that never had time to heal. The CT data also reveal no evidence that sediment compaction or later geological processes forced the tooth into the skull after burial, reinforcing the interpretation of a perimortem bite.
That analytical framework did not emerge in a vacuum. Earlier peer-reviewed work on tyrannosaurid bite marks found on Daspletosaurus remains from Dinosaur Provincial Park in Alberta, Canada, established methods for separating pre-mortem bites from post-mortem ones. The Daspletosaurus study showed that bite marks inflicted on a living animal leave different surface textures and fracture geometries than those made on dry or partially decomposed bone. Applying those criteria to MOR 1627 strengthened the case that the Edmontosaurus was alive, or had just died, when the tyrannosaur’s tooth broke off in its face.
Separate research on tyrannosaur-on-tyrannosaur feeding documented bite marks on Tyrannosaurus bones across multiple museum collections, confirming that these predators routinely left identifiable dental signatures on bone. That body of work gives paleontologists a reliable reference library for matching tooth marks to specific predator groups, which is how the MOR 1627 tooth was attributed to a tyrannosaurid rather than another large theropod. The spacing of the marks, the cross-sectional shape of the tooth, and the pattern of crushing in the surrounding bone all align with the powerful, thick-toothed jaws characteristic of tyrannosaurids.
In addition, the articulated nature of the Edmontosaurus skull helps rule out the possibility that the bite occurred long after death. Many scavenging traces appear on disarticulated bones that have been moved or scattered, but MOR 1627 preserves the cranial elements in life position. That anatomical integrity, combined with the CT-based assessment of fracture timing, underpins the conclusion that the bite was delivered during the final moments of the animal’s life.
Gaps in the fossil record and what to watch for next
Several questions remain open. The full CT scan datasets and exact tooth dimensions from MOR 1627 have not been released in publicly accessible repositories, limiting the ability of independent researchers to replicate the analysis or compare the tooth directly against known tyrannosaur dental measurements from other specimens. Provenance documentation beyond the initial BLM field records from the 2005 discovery is limited to citation trails rather than original collection logs, which means the precise stratigraphic position of the skull within the Hell Creek Formation is not as tightly constrained as it could be.
The comparative framework also has limits. Raw measurements from the Daspletosaurus bite-mark study and other tyrannosaur feeding research come from different formations, ages, and depositional environments. That makes it difficult to translate frequencies of certain bite types directly from one ecosystem to another. Hell Creek’s mix of floodplain, channel, and overbank deposits biases which bones preserve and how they weather, potentially skewing the apparent rate of facial bites in hadrosaurs compared with other regions.
Future work will likely focus on expanding the sample size of well-preserved hadrosaur skulls from the same time and place. Systematic CT scanning of additional Edmontosaurus and related hadrosaurid specimens could reveal subtle, previously overlooked bite traces beneath the bone surface, including partially healed injuries that never reached the outer cortex. Combining those data with high-resolution mapping of Hell Creek stratigraphy would help tie individual attacks to particular intervals of climate and environmental change.
Researchers are also calling for more open data practices surrounding spectacular specimens like MOR 1627. Making CT volumes, surface meshes, and detailed field notes available would allow multiple teams to test alternative interpretations, refine estimates of bite force and jaw mechanics, and explore whether the embedded tooth might be matched to a specific tyrannosaurid species. As more fossils are scanned and more datasets shared, paleontologists hope to move from isolated case studies toward a statistically grounded picture of how apex predators hunted at the close of the Cretaceous.
For now, MOR 1627 stands as a particularly vivid snapshot: a hadrosaur caught in the act of being bitten in the face by a tyrannosaur, its final struggle recorded in snapped enamel and crushed bone. That moment, frozen in stone for tens of millions of years, offers rare, direct evidence of the risks and violence that shaped life in the Hell Creek ecosystem-and a reminder that even the most familiar dinosaur predators still have new stories to tell through the fossils they left behind.
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*This article was researched with the help of AI, with human editors creating the final content.
