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Re: pterosaur launching tactics

----- Original Message ----- From: "Michael Habib" <mhabib5@jhmi.edu>
To: "Dinosaur Mailing List" <dinosaur@usc.edu>
Sent: Monday, June 09, 2008 12:25 AM
Subject: Re: pterosaur launching tactics

I might suggest that the relative brevity of the humerus in Q. provides less leverage for forelimb launch, but perhaps you guys don't rely strictly on this lever for your launch. Still, while I don't discount it, I'd like to see your version before guessing wrongly.

I note in passing, that for a wingspan increase of 2.3, the Qn humerus is 2.14 times the length of the Qsp humerus, while the r/u is only 1.95 times the length of the Qsp humerus. The latter ratio seems to be more a mechanism for increasing the aspect ratio of the larger animal than a launch related feature.

The uropatagium probably does provide some lift after the hindlimb push-off, but only after the hindlimbs have imparted force to the substrate for launch - again, see force plate data.

Agreed. The hips of pterosaurs aren't really suited for holding the limbs horizontal for long periods of time. The uropatagium area probably flew at a lift coefficient about half that of the brachiopatagium (in order to support the mass of the hindlimbs). Note that this is an unstable flight configuration, which can be (and usually is) an advantage for a flying vertebrate.

The animals don't have to launch from the typical "standing" stance. Nyctosaurus and Arthurdactylus, and other especially long-winged forms, can easily shift the hands relative to the cg, and vice versa.

Agreed. The further farward the hands can be placed relative to the shoulder, the lower the required launch accelerations. The polevault function of the forelimbs is a big help during launch.