Many of the giant pterasaurs that ruled the skies in the time of the dinosaurs had large elaborate crests. Several theories have arisen to their use, including helping with balance in flight. Now though a rare fossil of a juvenile pterasaur may provide some answers. The youngster had a crest still in the process of growing, lending weight to the theory that the purpose of these crests was as a display to attract mates.

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I guess that would fit in with some of the modern day animals behaviour.