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Re: Phylogeny of Maniraptora



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

Doesn't this make a perhaps unwarranted presumption that passive gliding
precedes active flight?

I said "one gradational pathway for the evolution of active flight"; I recognize that there are others. Many, many others. The hypothesis that passive gliding preceded active flight is one possible pathway. "Flapping start" models represent another pathway.


Why? Perhaps it used the forewings as stationary canards while flapping with the hindwings?

Yep, I'm not discounting that possibility. But again, using the hindlimbs for flapping implies a novel method of flight. This model may be aerodynamically viable, but was it biomechanically possible? And, as you note...


I only point out that it can't be discounted without investigation, and insofar as I know -- it hasn't been investigated yet.

I would add that I didn't say that four-winged flying was unlikely; just that the relatively short arms of _M. gui_, compared to _Archaeopteryx_ and other birds, and even to some other dromaeosaurids (including taxa that show no evidence of aerodynamic locomotion) undermines the assertion that its forelimbs were used as flapping wings in powered flight. Still, I'm happy to be proved wrong.


Perhaps large (non-vertebrate) dragonflies might be able to partially address this issue.

As I'm sure you're aware, dragonflies are highly adept fliers. I would add that multiple pairs of wings does appear to be the primitive condition for the first flying (pterygote) insects. As arthropods, the first insects also had the luxury of multiple appendages; vertebrates have to make do with a maximum of four (five including the tail).


Doesn't this presume that all pterosaurs incorporate the hindlimb into the flight membrane?

Oh no. I did say "may use". I'm aware that at least some pterosaurs had the flight surface supported only by the forelimbs.


Note that I personally think there were enough pterosaur niches to be filled and enough pterosaur species filling them that both conditions might well arise, with the independent condition more likely where yaw authority issues provided a need.

Agreed.



Tim

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