Fossil dinosaur leg's dazzling preservation

Scientists are investigating a fossil site called Tanis in North Dakota that records the day 66 million years ago when an asteroid hit Earth. Among the discoveries is a beautifully preserved dinosaur leg. The specimen features in a BBC programme called Dinosaurs: The Final Day. It will air on Friday 15 April at 18.30 BST on BBC One. In this clip Sir David Attenborough brings in expert Prof Paul Barrett to help him understand the significance of the fossil leg.

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