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Re: pteros have lift-off

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.

----- 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.