re: Flightless pterosaur indicators

[Tim Williams <tijawi@yahoo.com>]

It's worth considering that flightlessness in pterosaurs, if it happened at 
all, might have been promoted by an aquatic/marine ecology.  This would be 
analogous to what happened in the evolution of certain flightless birds, like 
hesperornithids.


So in this case the flightless pterosaur would not be doing too much walking, 
just swimming and maybe diving.  It all depends how amenable the pterosaur 
bauplan is to swimming or floating on the surface, and/or to diving (either 
foot-propelled or wing-propelled diving).


Cheers

Tim


--- On Wed, 24/3/10, David Peters <davidpeters@att.net> wrote:

> From: David Peters <davidpeters@att.net>
> Subject: re: Flightless pterosaur indicators
> To: "dinosaur mailing list" <dinosaur@usc.edu>
> Received: Wednesday, 24 March, 2010, 2:39 PM
> Seems to me three indicators might
> have to include:
> 
> 1. Lack of predators in the environment
> 
> 2. Any change in morphology that prevents flight
> including:
> a) reduction of wing length, 
> b) reduction of the pectoral girdle (and its anchoring
> muscles), 
> c) morphological changes that move the center of
> aerodynamic balance away from the wing root. 
> 
> 3. Death of the pterosaur    ;-) (had to throw
> that one in)
> 
> If pterosaur wings originally developed as secondary sexual
> characteristics (after all they can be folded and deployed),
> then perhaps they were retained in flightless forms
> (analogous to the Kagu), for the same usage. So, if we're
> going to find flightless pterosaurs, I think our best bet is
> to look for the ones with smaller shoulders. What the
> threshold dimensions might be I leave to the engineers and
> mathematicians. If anyone wants to figure those equations
> out, please contact me off list and we'll have a project. 
> 
> Or do pterosaurs also need large shoulders to walk around
> quadrupedally?
> 
> David Peters
> davidpeters@att.net
>