The dinosaur limb, complete with skin, is just one of a series of remarkable finds emerging from the Tanis fossil site in the US State of North Dakota. But it's not just their exquisite condition that's turning heads - it's what these ancient specimens are purported to represent, according to BBC.
The claim is that the Tanis creatures were killed and entombed on the actual day a giant asteroid struck Earth.
The day 66 million years ago when the reign of the dinosaurs ended, and the rise of mammals began.
Very few dinosaur remains have been found in the rocks that record even the final few thousand years before the impact. To have a specimen from the cataclysm itself would be extraordinary.
Sir David will review the discoveries, many that will be getting their first public viewing on BBC. Along with that leg, there are fish that breathed in impact debris as it rained down from the sky.
We see a fossil turtle that was skewered by a wooden stake; the remains of small mammals and the burrows they made; skin from a horned triceratops; the embryo of a flying pterosaur inside its egg; and what appears to be a fragment from the asteroid impactor itself.
"We've got so many details with this site that tell us what happened moment by moment, it's almost like watching it play out in the movies. You look at the rock column, you look at the fossils there, and it brings you back to that day," says Robert DePalma, the University of Manchester, UK, graduate student who leads the Tanis dig.
It's now widely accepted that a roughly 12km-wide space rock hit our planet to cause the last mass extinction.
The impact site has been identified in the Gulf of Mexico, off the Yucatan Peninsula. That's some 3,000km away from Tanis, but such was the energy imparted in the event, its devastation was felt far and wide.
