Re: Phylogeny of Maniraptora

["Tim Williams" <twilliams_alpha@hotmail.com>]

James R. Cunningham <jrccea@bellsouth.net> wrote:

> > At some stage, this is quite possible, if flapping was superposed upon
> > previous passive gliding.
>
> And your scenario is quite possible too.  It doesn't address which came
> first.  And perhaps neither avenue was exclusive to the other.

True.  Nevertheless, the participation of the hindlimb in powered flight 
implies a novel range of motion for the hindlimb, especially at the 
hip-joint.  As Greg Paul has noted, the more spherical femoral head of 
_Microraptor_ seems to suggest that the femur might have capable of greater 
lateral excursion; other theropods, including birds, show a more 
cylindrical-shaped head.

Modern arboreal "prosimian" primates show both cylindrical (tarsiers, 
galagos) and subspherical (avahi, sifakas, indri) femoral heads, and the 
latter allows improved femoral adbuction.  However, the less mobile 
cylindrical joint provides greater stability for the limb - an advantage 
when landing.

> > >Did the "four-winged" stage precede two winged animals, or are the
> > >"four-winged" theropods descended from theropods that sported only 
> pectoral
> > >wings?  There is probably no way of telling at this time.
>
> Why do we always use binary logic?  What's wrong with trinary?

If you have another hypothesis, I'd love to hear it.

Cheers

Tim

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