Researchers have identified what they say is the first known series of footprints made by an adult Tyrannosaurus rex in the south-west of North Dakota.
The trackway measures about 23 feet in length and comprises four three-toed prints — two left and two right — preserved in rock from the well-known dinosaur fossil area called the Hell Creek Formation. The prints have been dated to roughly 66.5 million years ago.
The discovery was made last year by a team from the Denver Museum of Nature and Science in Colorado in collaboration with scientists from Liverpool John Moores University in the United Kingdom, who recognized and documented the unusual sequence of prints.
Researchers described the find as the first known series of adult T. rex footprints, adding a new type of evidence to the fossil record in a formation already noted for its dinosaur remains. The discovery provides a rare direct trace of the animal's presence in the landscape at the end of the Cretaceous period.