First Adult T. Rex Trackway Found in North Dakota

Scientists confirmed the first-ever trackway of an adult T. rex in North Dakota, recording a 13-foot stride at a brisk-walk pace 66.5 million years ago.

Scientists have confirmed the first adult Tyrannosaurus rex trackway ever discovered, a 23-foot sequence of four three-toed footprints in the Hell Creek Formation on U.S. Forest Service land near Marmarth, North Dakota. The find was spotted by Kent Hups, a high school science teacher and amateur fossil hunter volunteering with the Denver Museum of Nature & Science field program. According to Good News Network, Hups co-authored the paper and said, "I never imagined that could lead me to a discovery like this," calling the trackway "the closest you get to a time machine."

Bones reveal anatomy, but a trackway captures behavior — a moment of an animal actually moving. "With a trackway, we can actually follow an animal as it moved across the landscape," said Tyler Lyson, senior curator of vertebrate paleontology at the Denver Museum of Nature & Science, in findings reported by both Good News Network and Space Daily. Isolated adult T. rex prints had been found before, and tyrannosaur trackways in Canada and Wyoming came from smaller animals, but a walking sequence from a full-grown rex had never been recorded. The attribution rests on the prints' exceptional size, the narrow angle between toe impressions, and the abundance of adult T. rex fossils in the surrounding rock, which published this week in the Journal of Vertebrate Paleontology leaves no other candidate.

The trackway records two left and two right footprints with a stride of approximately 13 feet between successive prints of the same foot. Feeding the stride and footprint size into standard locomotion equations, the team estimated the animal was walking at about 3.5 to 4.5 mph — roughly the pace of a brisk human walk — though Space Daily notes the prints are heavily weathered, making the speed figure approximate. The finding lands squarely in a long-running debate: biomechanical models have long suggested a running T. rex would have needed impossible leg muscle, and now the animal itself, as Space Daily puts it, has weighed in as "the only witness that was there," ambling along exactly as predicted.

The methods were as modern as the subject is ancient. The team documented each footprint with high-resolution 3D surface scanning, and lead author Peter Falkingham, a professor of paleobiology at Liverpool John Moores University, analyzed the trackway without ever seeing it in person — colleagues scanned the stones in the field and sent him the digital models, which he examined on his computer and in VR. Three of the four prints are expected to be recovered by helicopter this fall and transported to the Denver Museum of Nature & Science, which plans to share recovery updates with guests this winter. Sixty-six and a half million years later, the mud kept the receipt.