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Re: Senter 2006, Confuciusornis, and humeral mobility



Jaime Headden <qi_leong@hotmail.com> wrote:

>   These birds do not suffer the unfortunate condition of having evolved in 
> and around the point where flapping flight was being developed, including the 
> absence of an alula (for landing controls) or even
>  a developed retricial fan, much less a perching foot. These birds are (or 
> were) either terrestrial or uncomfortably semi-arboreal.


IMHO, this is a point that can't get emphasized enough.  Although the
feathers of early birds are identical to those of modern birds, the
musculoskeletal elements of the flight apparatus still had a long way
to go.  So when it comes to flight behavior, to compare early birds to
modern birds is drawing a long bow indeed.

The same "unfortunate point" mentioned by Jaime also applies to the
forebears of birds - which is why I'm so skeptical of wing-assisted
incline running (WAIR) being an ancestral behavior for the origin of
avian flight.


> If the latter, the development of a means of controlling attitude and rate of 
> descent (as well as projection during aerial travel) would be almost 
> certainly more important than forms of steady flight
> controls. If so, the quality of marine birds who spend most of their lives on 
> the wing, and have adaptations other extant birds lack to enable this, is 
> almost certainly irrelevant.

I'm actually quite comfortable with the idea of archaeopterygids and
confuciusornithids being gliders, not flapping flyers.  After all, it
is generally accepted that _Microraptor_ couldn't fly, despite the
"advanced" aerodynamic morphology of its feathers.  So why do we try
so hard to convince ourselves that _Archaeopteryx_ and
_Confuciusornis_ could fly?



Jason Brougham <jaseb@amnh.org> wrote:

> Please watch these Sooty Shearwaters using WAIR to climb trees so that
> they can takeoff. These things have webbed feet, no arboreal adaptations,
> and apparently don't have the power to takeoff from the ground:
>
> http://www.youtube.com/watch?v=Cjmtt_B_i4A
>
> Can't you picture Confuciusornis doing the same thing?


I can't, no.  Shearwaters are neornithean birds, with a highly evolved
flight musculature - even if these birds are incapable of a vertical
take-off.  The osteology and musculature is far more specialized than
that of basal birds like _Confuciusiornis_, and WAIR requires a
complete wingstroke.




Cheers

Tim