First known adult T. rex trackway discovered in North Dakota

Palaeontologists have discovered what is believed to be the first known trackway left by a fully grown Tyrannosaurus rex, offering rare evidence of how the dinosaur moved.

The discovery consists of four connected footprints preserved in the badlands of southwestern North Dakota, near the Montana border.

The tracks, described in a new paper published in the Journal of Vertebrate Paleontology, are about 66.5 million years old.

Until now, only two confirmed footprints from adult T. rex had been identified worldwide, one in New Mexico and another in Montana. Both were isolated tracks, providing little information about the dinosaur's movement.

“Bones tell us an enormous amount about these animals, but footprints capture a moment of behaviour. With a trackway, we can actually follow an animal as it moves across the landscape. That is incredibly rare for T. rex,” Tyler Lyson, senior curator of vertebrate palaeontology at the Denver Museum, said in a statement.

Researchers found the new tracks last year on federal land near Marmarth, North Dakota. Each footprint measures about 3 feet (0.9 metres) long, with roughly 13 feet (4 metres) between successive steps. Their size and shape helped researchers identify them as belonging to an adult T. rex.

The team used high-resolution 3D scanning to document the footprints. The scans allow researchers to study the tracks digitally and create physical replicas without disturbing the original site.

The spacing of the tracks also provided clues about the dinosaur's speed. Researchers estimate that the T. rex was moving at around 3.5 to 4.5 mph, roughly the pace of a brisk human walk. They cautioned that the estimate is not exact because weathering and erosion have altered the footprints over millions of years.

Researchers plan to recover three of the four footprints later this year and transport them by helicopter to the Denver Museum of Nature & Science for preservation and further study.