A British palaeontologist has found what he thinks is a preserved Tyrannosaurus rex footprint.
The metre-square, three-toed track was discovered in the Badlands of Montana, US, an arid landscape that has yielded many of the finest dinosaur specimens.
Dr Phil Manning, from the Manchester Museum, University of Manchester, first saw the impression last year.
He returned to the US in July to study the print further, and now plans to publish details in a science journal.
Dr Manning said that finding dinosaur trackways was an important addition to our understanding of how the great beasts lived more than 65 million years ago.
End of story
"People have been trying to find these tracks for over 100 years. And these are really quite special because they put the animal at the scene of the crime," he told the BBC's Inside Out programme.
"A live animal leaves tracks - bones can be transported after death, so it really puts the animal in the context of where it used to live."
The print was found in rocks that geologists refer to as the Hell Creek Formation.
This is a layer of sediments lying to the east of the Rocky Mountains that consists of greyish sandstones and shales with interbedded lignites. It formed at the very end of the age of the dinosaurs - and is probably most famous for its T. rex fossils.
Dr Manning's assessment of the print, together with drawings and photos, will be submitted to a scientific journal for peer review.
The Manchester researcher said he could not say he had found a T. rex print until others had had a chance to study his findings.
Age and size
"It could only be made by one of the two species known from Hell Creek - either the Nanotyrannus or its bigger relative, Tyrannosaurus rex. The size of the footprint at 76cm in length suggests it is more likely to be the latter," he explained.
There is one previous claim for a T. rex footprint in the scientific literature. The track was discovered in New Mexico in 1983 and published 11 years later.
"It is never possible to be certain of the animal that made fossil footprints as they do not die conveniently at the end of their tracks," commented Dr Angela Milner, the associate keeper of palaeontology at London's Natural History Museum.
"However both these prints occur in rocks of the right age, they definitely were made by large carnivorous dinosaurs - and the only one that was large enough to leave such a huge footprint was Tyrannosaurus rex."
Inside Out is broadcast on BBC One, at 1930, on Wednesday, 10 October. Viewers outside the North West region can watch the programme on Sky channel 978 or online at www.bbc.co.uk/insideout