RE: Fw: Dinosaurs and birds

[Tim Williams <twilliams_alpha@hotmail.com>]

Don Ohmes wrote:

> And to change the subject slightly-- has anybody formally proposed a 
> specific scenario/environment >for the establishment of synchronous use of 
> the forelimbs, as opposed to an alternating pattern? >Isn't that necessary 
> to start all this anatomical sophistication in motion?

I'm not sure I'm answering your question correctly (so apologies in 
advance)...  The "Predatory Stroke" hypothesis (Gauthier and Padian, 1985), 
for example, proposes that synchronous motion of the forelimbs actually 
preceded the evolution of the avian flight stroke.  Under this hypothesis, 
the maniraptoran ancestors of birds are thought to have captured prey using 
both forelimbs at once; and the anatomy of the joints allowed both the 
forelimbs to be extended rapidly toward the prey.  In fact, this hypothesis 
proposes that the prey-catching motion of the forelimbs (the "predatory 
stroke") is biomechanically homologous to the avian flight stroke, with a 
few modifications.

I hope that helps.

Reference:

Gauthier, J. A., and Padian, K. (1985). Phylogenetic, functional, and 
aerodynamic analyses of the origin of birds and their flight.  In: M. K. 
Hecht, J. H. Ostrom, G. Viohl, and P. Wellnhofer, (eds). The beginnings of 
birds: proceedings of the international _Archaeopteryx_ conference, 
Eichstätt 1984. Freunde des Jura-Museums, Eichstatt, Germany. p.185-197.


Cheers

Tim

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