The mark that was left in a once dinosaur rich area of Montana could be the footprint of a Tyrannosaurus rex.
Either a Nanotyrannus or a T. rex could have generated a track of that size. Whatever it was, it was big.
If confirmed, it would be the second known T. rex print to ever be discovered. The first was found in 1983 in New Mexico.
The track is three feet wide and estimated to be 65 million years old.
The site of the print is being kept a secret until suitable measures can be taken to preserve it.
To see an image of the track click here.