Paul Cambridge wrote:
I know theories abound about mating display purposes,You may well have just answered your own quetsion.
but if an animal is working so hard to LOSE pounds, i.e. the hollow tubular bones and such, wouldn't it be self-defeating to have these crests?Not necessarily. Like other animals, one sex may have sported the biggest display that they could get away with. One thing they were probably NOT used for is yaw control in the air. None of the really long-necked azhdarchids have ever been found sporting a large crest, and I venture to speculate that none will be, due to the severe problems with yaw reversals caused by the erratic flow reversals on the crest (very similar to the erratic yaw forces created by flow reversals on Piper Cherokee nosewheel fairings). It seems that the hollow tubular bones may have been more a result of maximising resistance to bending and torsion than an effort to reduce weight. With the caveat that the azhdarchids had a modification in phalanges IV-2&3 that was intended to reduce resistance to torsion (to compensate for the relatively reduced length of the outer wing). As Paul MacCready says, putting a crest on a long necked pterosaur is like trying to fly an arrow with the feathers on the front end.
It must have been a pain to get of the ground in the first place being of that body size.Well, first off they had tiny bodies. Even the chunky Quetzalcoatlus species measured only 12.25 inches more or less from the notarium socket to the hip socket (compared to a neck length of about 4.85 feet). Secondly, it would appear that both Q species and Q northropi could launch handily even in today's atmosphere, so I venture to suppose that it would have been just as easy for Pteranodon.
All the best,