Paul Sereno, a paleontologist at the University of Chicago, adding the toe claw to the skeleton of the new tyrannosaur Raptorex.
"If I was a tyrannosaur facing another tyrannosaur face-to-face, I'd say the only real strategy is to wait for an opening and then go straight for the head," he said.
The new fossils shed light on debates about tyrannosaur evolution.
If so, he, she or it would not be the only new tyrannosaur in the news at the moment.
Samson—actually reckoned to be a female—is thought by some palaeontologists to be an example of a new tyrannosaur species, not the familiar rex.
The imprint is well defined and deeply embedded in the sandstone riverbed, as if the tyrannosaur had walked there only last week.
