Re: Pterosaur wing membranes

[Michael Habib <mhabib5@jhmi.edu>]

> Yes, and most (but not all) pterosaurs seem to have been marine 
> soarers, where conditions are right for dynamic soaring and thermals 
> are weak. However,  they can gain altitude in any thermals that exceed 
> their minimum rate of sink.

Naturally, though it might be a bit tricky for large pterosaurs to stay 
in thermals for very long, simply owing to the relatively small size of 
most thermals and the presumably high cruising speed of most 
pterosaurs.  (For those that do not generally study flight, animals 
must stay not only in the thermal's bounds, but must remain near the 
middle of the thermal.  The air on the outside of a thermal is actually 
moving downward relative to the ground.)  I seem to recall that some 
marine thermals are pretty large, however.

I actually did a short paper (for a class some time ago, perhaps it 
will be something more some day) looking at the climate of the Western 
Interior Seaway, and the effects of that local climate on pterosaurs 
(specifically Pteranodon).  One helpful bit of atmospheric alteration 
was that the Eastern margin of the seaway was a giant evaporation pan.  
The humid air would have risen quite quickly (owing to its low 
density), and created giant humidity thermals that the animals could 
ride on to get up to cruising altitude before heading out to sea to 
feed.


Cheers,

--Mike H.