These Four Giant Dinosaur Footprints Discovered in North Dakota Might Represent the First Trackway Made by an Adult T. Rex Ever Found

Four enormous three-toed impressions uncovered in southwestern North Dakota may preserve an unusually rare moment in the life of Tyrannosaurus rex: the passage of a fully grown animal across a wet, wooded landscape about 66.5 million years ago. Paleontologists say the aligned prints could form the first trackway attributed to an adult T. rex, rather than a single isolated mark. The discovery points to an animal that left several consecutive steps behind in ancient ground that later became fossilized.

The discovery began with a high school teacher volunteering at a paleontological excavation. The teacher noticed what appeared to be a large dinosaur footprint and brought it to the attention of researchers. What initially looked like one promising trace ultimately became a sequence of four giant tracks, each showing the animal's characteristic three forward-pointing toes. Finding several prints in sequence gave the team more evidence to examine than one mark alone could provide.

That sequence matters because tracks can document motion in a way that skeletons cannot. A fossil bone can identify an animal and hint at its size, but a run of footprints can retain evidence of its direction, stride and progress through a particular place. In this case, the marks suggest that a massive predator was moving through terrain that was marshy and forested during the closing chapter of the age of dinosaurs. They preserve a fleeting record of behavior from a creature known more often through bones than through evidence of its steps.

The team estimates that the animal was not rushing. Based on the spacing and form of the tracks, it calculates a walking speed of roughly 3.4 to 4.5 miles an hour. The estimate offers a picture of a large theropod traveling at a steady pace, though it does not by itself establish what prompted the journey or where the animal was headed. The tracks record movement, but not the destination, circumstances or duration of the dinosaur's passage.

Researchers presented the find in a paper published September 8 in the Journal of Vertebrate Paleontology. Their interpretation is especially notable because evidence tied to adult T. rex feet has been exceptionally limited. Before this North Dakota work, only two tracks thought to have been left by adult T. rex individuals had been reported, with one from New Mexico and another from Montana. The newly described set would add a rare multi-step example to that small body of evidence.

The first reaction inside the excavation was not immediate certainty. Hups believed the original impression had been made by T. rex, but paleontologist Lyson was more cautious when told about it. That skepticism reflects the difficulty of assigning a footprint to one dinosaur species, particularly when the fossil record includes incomplete traces and when very few accepted adult T. rex prints are available for comparison. The later identification rests on examining the entire set of impressions, not merely on the initial discovery.

The four-print trail therefore carries greater weight than an isolated impression would. Repeated tracks can help researchers assess whether the shape, size and spacing belong together as the work of one walker. Even so, the proposed identification remains an interpretation built from the available physical evidence, not a direct observation of the animal, and further study will determine how strongly it stands against alternative explanations. The rarity of comparable adult tracks makes both the claim and the need for careful review significant.

For North Dakota, the site also provides a localized view of an ancient environment rather than a museum image of a dinosaur alone. The prints place a giant animal on the ground in a landscape that was then wet and wooded, turning a distant geological period into evidence of an actual passage. They may help researchers compare how large dinosaurs moved across different Late Cretaceous settings in the region. The setting is central to the discovery because the old, swampy ground preserved the trace left by the animal.

Attention will now center on the detailed study of the trackway and on whether additional footprints emerge from the same area. More material could sharpen estimates of the trackmaker's anatomy and movement, or complicate the current reading. For now, the North Dakota impressions offer a rare candidate record of an adult T. rex walking through a long-vanished swampy forest, with four steps still visible after millions of years. The find may ultimately clarify whether the trackway represents the strongest known evidence of its kind.

Source: Smithsonian Magazine