The plesiosaurs are extinct marine reptiles that patrolled the world's seas
Media playback is unsupported on your device
Video

Ancient reptile 'swam like a penguin'

The plesiosaurs - marine reptiles that patrolled the world's seas when dinosaurs ruled the land - swam much like penguins by using their flippers to "fly" underwater, say scientists.

It resolves a debate that began nearly 200 years ago.

  • 18 Dec 2015