Adult T. rex: a 66.5-million-year-old track discovered in the United States

Four fossilized footprints discovered in North Dakota represent the first known track attributed to an adult Tyrannosaurus rex. Dating back approximately 66.5 million years, they provide researchers with a rare snapshot of the movement of this large predator.

The discovery is detailed in a study published on September 9 in the Journal of Vertebrate Paleontology. The track, measuring about seven meters in length, includes two left footprints and two right footprints unearthed in the Hell Creek geological formation in the southwestern part of the state.

Each footprint measures nearly 91 centimeters. The distance between the steps reaches approximately four meters, leading the team to estimate that the animal was moving at a speed of between 5.6 and 7.2 km/h, comparable to a human walking pace. This estimate remains approximate due to the erosion of the tracks.

Scientists consider the T. rex to be the most likely creator of the track due to the exceptional size of the footprints, the narrow shape of the toes, and the abundance of fossils from this species in the area. Two isolated footprints had previously been attributed to adults, but no comparable sequence of steps had been described.

The site was discovered in 2025 near Marmarth by Kent Hups, a teacher from Colorado and a volunteer at the Denver Museum of Nature & Science. Researchers subsequently digitized the tracks in high resolution for study and to create three-dimensional reproductions.

Three of the four footprints are to be airlifted and transported to the Denver museum. Unlike bones, this track directly preserves a moment of the animal’s behavior as it traversed the landscape.