Re: Pterosaur wing membranes

[jrc <jrccea@bellsouth.net>]

----- Original Message ----- 
From: "Michael Habib" <mhabib5@jhmi.edu>
To: <dinosaur@usc.edu>
Sent: Friday, April 14, 2006 8:58 PM
Subject: Re: Pterosaur wing membranes


> However, low wing loadings are terrible for dynamic soaring (which is why 
> albatrosses have high wing loadings).  Pterosaurs were pretty obviously 
> built for dynamic soaring (with incredibly high aspect ratios, for 
> starters).

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.

> Bats are, in fact, not very good at gliding, all told.  Most cannot glide 
> much at all, and the flying foxes glide very slowly.

Because of their relatively light wing loading.

>  At higher wing loadings, an animal glides faster (getting from point A to 
> point B more quickly), without having to use more energy.  The amount of 
> vertical travel remains unchanged, they just get to where they're going 
> faster.

Horizontal travel remains unchanged too.  For a given wing planform, 
increasing the weight does not reduce the gliding range.  You glide just as 
far, but as you say, you get there more quickly.

>  That doesn't mean gliding is no good to large bats; they obviously use it 
> when appropriate and it saves energy.  Vultures also glide pretty 
> frequently.  But, all told, they're not good at covering distance or 
> riding shears.  Rather, such low-loading animals are good at loitering.
>
> Pterosaurs, by contrast, were great at gliding and dynamic soaring, but 
> probably pretty poor at loitering (compared to a vulture, that is, which 
> is a very high bar).

It would take a stronger thermal for them to loiter.  But they would be 
superbly adapted for migrating, able to cover a lot of distance in a day.
> Cheers,
>
> --Mike Habib