A high school science teacher from Colorado has helped give paleontologists something they had never had before: a sequence of footprints likely left by a fully grown Tyrannosaurus rex. The trackway, described in a study in the Journal of Vertebrate Paleontology published Sept. 8, stretches about 23 feet (7 meters) across the Hell Creek Formation of southwestern North Dakota and dates to about 66.5 million years ago, shortly before the asteroid impact that ended the age of dinosaurs.

Kent Hups, who teaches at Northglenn High School and volunteers as a research associate at the Denver Museum of Nature & Science, spotted the first prints in July 2025 while volunteering on a museum dig. Each of the four three-toed footprints is roughly 3 feet (1 meter) long. From a stride of about 13 feet (4 meters), researchers estimated the animal was walking at about 1.5 to 2 meters per second, roughly 3.4 to 4.5 mph, about the pace of a brisk human walk.

The find matters because bones show what a dinosaur looked like, while tracks record what it was doing. Study co-author Tyler Lyson said "footprints capture a moment of behavior," as quoted by Fox Weather. For the most famous predator in the fossil record, that kind of behavioral snapshot had been missing.

A Teacher's Eye in the Badlands

The trackway lies on the Dakota Prairie Grasslands, federal land managed by the U.S. Forest Service near Marmarth in Slope County. Hups, who has searched for fossil footprints as a hobby for about three decades, noticed wedge-shaped lumps of rock that looked like giant toes. He initially found two prints in the open, one more eroded than the other, according to CNN's account of the discovery.

Hups said he always tells his students that "science starts with curiosity, passion and careful observation."

The museum's paleontologists were not immediately convinced. Lyson, senior curator of vertebrate paleontology at the Denver Museum of Nature & Science, noted that weathered rocks can take on all sorts of shapes. He marked spots in the dirt where additional prints should be if the pattern was real, and the team dug up a third and then a fourth.

The team returned to the site this summer and found a fifth print that was not included in the published study. Lyson told CNN the new print removes any doubt in his mind that the trackway belongs to a T. rex.

The study's lead author, Peter Falkingham, a paleobiology professor at Liverpool John Moores University in England, never visited the site. Colleagues scanned the tracks in 3D and sent him the data, which he examined on his computer and in virtual reality, according to Discover Wildlife.

The Case for a Full-Grown Tyrannosaurus

The paper describes the trackway as "likely attributable" to an adult T. rex, careful wording that reflects how the identification was made. No bones were found with the prints. Instead, the team pointed to the tracks' very large size, the narrow angle between the toe impressions, and the abundance of T. rex fossils in the surrounding rock, according to Sci.News.

Lyson told CNN that only two dinosaurs in the Hell Creek Formation were big enough to leave prints that size, T. rex and the duck-billed Edmontosaurus, and that their feet are very different. The prints have three slender toes with a longer middle digit, similar to T. rex feet.

Earlier finds were more limited. Isolated footprints linked to adult tyrannosaurs were described from New Mexico in 1994, and Montana in 2008, but none recorded more than one step. Tyrannosaur trackways found in Canada and Wyoming were made by smaller animals, either younger individuals or related, smaller species.

The prints survived unusually. Sand filled depressions left in soft, muddy ground and hardened into calcium carbonate-cemented casts. When the softer surrounding rock later eroded, the tougher casts were left exposed. That process also fractured them, so the prints preserve little fine anatomical detail beyond overall size and toe count.

A Walking Pace, Not a Top Speed

The trackway provides the first direct measurement of an adult T. rex's stride. That is valuable, but it does not settle long-running debates over how fast the animal could run.

Thomas Holtz Jr., a vertebrate paleontologist at the University of Maryland, College Park, who was not involved in the study, told CNN that the estimated speed is far below the animal's maximum, because preserved tracks likely formed in wet soil and animals move fastest on firm ground. He still called the find significant, describing it as "perhaps the first definitive Tyrannosaurus rex trackway sequence."

The evidence has clear limits. This is a single trackway from one animal, and the weathered prints limit what can be said about foot anatomy. The speed estimate comes from stride and foot length, not direct observation. The study is peer-reviewed, but the fifth print found this summer has not yet been formally described.

Recovery Plans and What Fossil Hunters Should Know

Three of the footprints are to be recovered by helicopter later this year and taken to the Denver Museum of Nature & Science, where Lyson said researchers plan to analyze them further, including for any skin impression data.

For amateur fossil hunters, the story is both an encouragement and a caution. Collecting vertebrate fossils such as dinosaur bones and tracks on federal land generally requires a permit and is limited to qualified researchers working with approved institutions. Anyone who spots what looks like a fossil should photograph it, note the location, and contact a museum or the land management agency rather than digging it out. Removing fossils can destroy the context that made this trackway so valuable to science.

Hups told CNN he hopes more people look harder at strange-looking rocks, calling fossil tracks the closest thing we have to a time machine.

The next milestones are the helicopter recovery and a formal description of the fifth print, which could strengthen the case for the trackmaker and refine stride and speed estimates.

The bottom line: a teacher's sharp eye produced the first known series of footprints likely made by an adult T. rex, showing the predator walking at an ordinary pace across a muddy floodplain. The tracks add behavior to a story long told only by bones, but they capture a single walk rather than the full range of how T. rex moved.

What Readers Want to Know

What did the teacher find?

Kent Hups, a science teacher at Northglenn High School in Colorado, found a trackway of four three-toed footprints in North Dakota's Hell Creek Formation. Researchers say it was likely made by an adult Tyrannosaurus rex.

Is this the first T. rex footprint ever found?

No. Isolated footprints linked to adult tyrannosaurs were described in 1994 and 2008. This is the first known trackway, or sequence of steps, attributed to an adult T. rex.

How fast was the T. rex moving?

Researchers estimate about 3.4 to 4.5 mph, similar to a brisk human walk. An independent expert noted this likely reflects a walk on wet ground, not the animal's top speed.

How do scientists know it was a T. rex?

They relied on the prints' very large size, the narrow angle of the toes, and the abundance of T. rex fossils in the same rock layers. No bones were found with the tracks, so the identification is described as likely rather than certain.

Where will the footprints go?

Three of the prints are to be recovered by helicopter later this year and taken to the Denver Museum of Nature & Science.

Can people collect fossils where the tracks were found?

The trackway is on U.S. Forest Service land, where collecting vertebrate fossils generally requires a permit. Anyone who finds a possible fossil should document it and contact a museum or the managing agency instead of removing it.