RE: vaulting pterosaur launch, questions

[Tim Williams <twilliams_alpha@hotmail.com>]

Michael Habib wrote:


> True; it has been assumed as the "basal" launch style by many workers.
> I'm not sure why that is, other than perhaps tradition built on some
> misunderstandings.


I'm sure he wasn't the first, but the 'running take-off' was discussed by 
Speakman (1993).  It's based on the relatively puny pectoral muscle mass of 
_Archaeopteryx_.  The argument runs that having flight muscle mass at or below 
16% of total body mass renders the bird incapable of a stationary take-off.  
_Archaeopteryx_'s is estimated at 9% - so it's well below the cut-off.  Grebes 
are said to have a flight muscle mass below 16%, which is why they require a 
requiring a "taxiing" run in order to become airborne.  Speakman doesn't 
necessarily endorse this line of reasoning; and the grebe example comes from 
Marden (1987).


> Birds also don't receive
> much limb excursion from the femur any longer, so shortness carries
> limited cost (stride length is largely unaffected).


Yes.  The kinetics do change, especially during rapid progression - leading to 
what's been called "Groucho running".    :-)


Refs


Marden, J. H. (1987).  Maximum lift production during take-off in flying 
animals.  J. Exp. Biol. 130: 235-258.

Speakman, J.R. (1993).  Flight capabilities in _Archaeopteryx_.  Evolution 47: 
336-340.



Cheers

Tim
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