The 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 purport to represent. The claim is 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. The BBC has spent three years filming at Tanis for a show to be broadcast on...