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Re: CNN: how first birds flew



gejd@concentric.net wrote:

> Although I think it unlikely that in very early feathered theropods the
> wing feathers could have made much addition to spead, maneuverability
> is a more likely candidate for a characteristic that would give the bearer
> an advantage. The positioning of the feathers on the arms allows considerable
> leverage. Gauthier was quoted in an article as saying that "a physicist" had
> calculated the effects of protowings as maneuvering tools about 10 years ago..
> Can anyone give me a citation for the article by "the physicist"? I have
> not been able to find it.
> -Gus Derkits

Gus,Here's a snippet of an on-going conversation I've been having with another 
list
member that's pertinent to your suggestion.  Also, Mary sent me a copy of the 
Nature
article.  I found it interesting.  If anyone has a reference for 'the physicist'
article, I'd love to read it as well.
Jim

> >My (jrc) personal opinion is that earlier birds used their wingtip and tail 
> >tip
> >tufts to increase their manueverability but not their running speed.  As
> >a rough analogy, imagine running as fast as you can while holding a
> >slack rope attached to a car matching your speed.  Now imagine what
> >happens when the car speeds up and applies additional thrust to your
> >body.  Legs have a natural powered pendulum frequency that isn't going
> >to change when supplemented by thrust from the wings.  However, directed
> >thrust from the wings can increase the zenith angle the legs can acheive
> >before losing traction, so can increase maneuverability.  I don't know
> >if anyone has looked at that in depth, but they should.

> On this I agree: and in fact I would suggest that this situation goes at
> *least* back to the common ancestor of dromaeosaurids and birds, and
> possibly to the common ancestor of oviraptorosaurs and the dromaeo-bird
> clade.  This could well explain (for example) the condition in _Caudipteryx_.

> >(jrc) Caudipteryx weighs in heavily in my thinking, although I had formed my
general
> >opinion before I became aware of that animal.  I don't think Caudipteryx is 
> >at
> >the beginning of the chain either, though I readily admit to being very weak 
> >in
> >phylogeny (I don't even know if I spelled it correctly).  I would suggest 
> >that as
> >more fossils of other species with tip tufts become available, that the 
> >structure
> >of their feet should be investigated as well.  I would welcome your input on
> >references I would find helpful on the dromaeosaurid, oviraptor, bird
> >connections.