Re: pteros have lift-off

[jrc <jrccea@bellsouth.net>]

northropi has a considerable part of the wing skeleton preserved, including 
the articular elements that are important to the launch.  The missing bits 
are allometrically scaled up from the smaller Qsp.  The known bits are 
enough to demonstrate that the quad launch is feasible for the big version. 
By extrapolating from the similarities in the known Hatz humerus, I would 
expect that the same is true for Hatz.  Like David M says, think of a 
pterosaur launch as a modified downstroke.  The outer wing is already 
starting to operate as an opening/lifing device as it begins to unfold very 
early in the cycle.  The quad launch also has the advantage of placing the 
torso in a suitable position for generating an appropriate stroke plane. 
For pterosaurs, that is not true of the bipedal launch. Other comments 
inserted below.
JimC

----- Original Message ----- 
From: "David Peters" <davidpeters@att.net>
To: "Michael Habib" <mhabib5@jhmi.edu>
Cc: "DML list" <dinosaur@usc.edu>
Sent: Monday, January 12, 2009 12:04 AM
Subject: Re: pteros have lift-off


> Not sure we  have any complete giant pterosaurs. All such reconstructions 
> are  scaled-up versions of the man-sized ones and smaller, are they not?
> Since the dp-crest varies so much in pterosaurs, does this tell us 
> anything about their launch mode? Does a warped or a hatchet-shaped 
> deltopectoral crest change things?

Yes.  The pterosaurs with dp crest shaped like that of quetz and hatz will 
be able to achieve higher launch weights.

> Have you compared "upper deckers" (short scapulae/long coracoids)  with 
> "bottom deckers" long scapulae/short coracoids)?

Yes.  As a generality, the bottom deckers have realigned the downstroke 
muscles to make their contraction path more horizontal (which does not limit 
their downstroke production due to the reshaping of the dp crest and 
coracoid flange).  They do this to allow a more effective stroke path for 
the upstroke muscles, so that the power of the upstroke is increased.

JimC