Re: bottom decker?? pteros

["James R. Cunningham" <jrccea@bellsouth.net>]

david peters wrote:

> Two cladistic facts do seem to emerge however. First: the clade that includes 
> azhdarchids and their ancestors among the dorygnathids appears to have a 
> coracoid that flares ventrally, while the clade that includes all of the 
> sharp-nosed germanodacs, tapejarids, pteranodontids, etc., does not have this 
> flare.<

This may be related to wingloading.  I haven't looked enough at the
other species to form a solid opinion.

> Second: the pterosaurs which appear to be adapted to soaring, such as the 
> ornithocheirids in one clade and the pteranodontids and nyctosaurs in 
> another, appear to have a shorter scapula than coracoid, and thus would all 
> be top-deckers.<

I have difficulty in seeing how anything could be more specifically
adapted to soaring than Quetzalcoatlus.  Perhaps, you meant adapted to
extraction of other sources of atmospheric energy which can be used for
soaring?  There are a number of different sources of soaring energy, and
a number of different techniques for extracting it.
 
> Airplanes with high or low wings usually have a reason other than flying for 
> them.

True.  Most of the time, its marketing.

> and in ease of maintenance (preflighting under the wing in a stance or a deep 
> crouch).

Low wings are much easier for maintenance.  You can lie down to work
underneath the wing.  In high wing planes you wind up in an awkward
position when working under the wing.  Visibility is about the same in
both types.  In both types, when you want to watch the ground you watch
it at a quartering angle about 45 degrees out to the front, side, and
down.  You tend to do this in order to reduce the rate at which stuff is
sweeping across your field of view, so the wing winds up being generally
out of the way either way.

> The reason Quetz. has a lower glenoid has more to do with its terrestrial 
> adaptations.

I do disagree with this.  In Quetz, the lower glenoid appears to me to
be related to the high wingloading and flapping power.  Moving the
glenoid downward allows a more powerful upstroke.  Extending the dp
crest further down allows a more powerful downstroke with muscles that
are operating more horizontally along the more horizontal coracoid. 
It's a way to get more bang for the buck without increasing the depth of
the torso.

>In my opinion, which differs from Jim's, Q. spent alot of time in water where 
>it was a bottom-feeder aided by its huge size, long rostrum and long neck, 
>rather than feeding while soaring. And it came from a long line of similarly 
>adapted pterosaurs of phylogenetically increasing size, driven by competition 
>into untapped niches in ever deeper waters.<

As David mentions, he and I differ here, but as he also knows, I like to
see different avenues of investigation remain open, so would not dream
of trying to dissuade him from investigating that hypothesis.  Rather, I
encourage it.
Jim