The fossilised fin of an ichthyosaur has given up an ancient secret: it seems the massive marine predators were very, very quiet. In a recent Nature paper, a team led by Swedish scientists describe the delicate serrations on the trailing edge of the one-metre-long fin. Owls use a similar wing structure, the team note—and are famously silent swoopers. The fin of the ichthyosaur also had a flexible, fleshy tip, further cutting down on acoustic and hydrodynamic disturbance and allowing for “stealthy searches and pursuits”.
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