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Re: Phylogeny of Maniraptora




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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