Re: 11th specimen of Archaeopteryx

[Jason Brougham <jaseb@amnh.org>]

A friend once suggested a hypothesis to me.  He proposed that the asymmetrical 
vanes on primary feathers may allow tighter folding of the wing. I personally 
don't really see why that would be - since the proximal, or trailing, vane 
remains broad and  is overlapped by the more proximal primaries. But perhaps 
having a  slender leading vane on the distalmost primary helps protect that 
feather and the ones behind it from fraying? I have no idea.


On Oct 24, 2011, at 2:31 PM, Matthew Martyniuk wrote:

> (meant to send this to the list...)
> 
> Sure, some things are more uncertain than others. But which of these
> hypotheses concerning the possible asymmetrical remige functionality
> is currently better supported by evidence?
> 
> 1) Lift generation for arboreal assistance (WAIR, or something similar)
> 2) Aiding in turning while running
> 
> How many studies have been done on the role of asymmetry in each function?
> 
> Scott Hartman wrote:
> "And finally, asymmetrical feathers are in no way directly linked to an
> arboreal lifestyle."
> 
> I never said they were. But the proponents of the arboreal lifestyle
> are the only ones with a wealth of studies and research on their side.
> There are plenty of papers discussing WAIR. I'd be curious to read
> those for turning, especially since in modern birds, even those that
> use their wings for turning, the feathers are not aerodynamic, and
> there was apparently no selective pressure to retain asymmetry for
> this purpose. If we're doing science, when there are two competing
> hypotheses, one backed up by current studies (WAIR) and one not
> (turning), the response should not be "well, we have no idea what they
> were for." The response should be "current research suggests WAIR is a
> likely use for asymmetrical feathers while alternate hypotheses
> require more investigation."
> 
> As Mike said above, there is no evidence to suggest that asymmetry was
> the ancestral condition, and in fact there's evidence against it
> unless you consider caudipterids and Sinornithosaurus to be
> secondarily flightless.
> 
> What gets me is that people keep citing "lack of arboreal features",
> while discounting feather asymmetry as one, despite the fact that no
> alternate interpretations of that character have been seriously
> investigated. If Archie had symmetrical feathers but a reversed
> hallux, it would be just as easy to say that the hallux is not an
> arboreal feature and that it would be possible to think up alternate
> uses for it, so therefore Archie has no arboreal features. "The
> asymmetry is not an arboreal feature because Archie has no other
> arboreal features" does not strike me as a very sound
> counter-argument.
> 
> Matt
> 
> On Mon, Oct 24, 2011 at 1:54 PM, Mike Keesey <keesey@gmail.com> wrote:
>> On Mon, Oct 24, 2011 at 10:51 AM, Matthew Martyniuk <martyniuk@gmail.com> 
>> wrote:
>>> 
>>> We need to learn a lesson from the BANDits; it's not enough to shoot
>>> down a hypothesis without proposing any alternative.
>> 
>> On the other hand, there are cases where we have to admit, "We don't
>> know [yet]."
>> 
>> --
>> T. Michael Keesey
>> http://tmkeesey.net/
>> 

Jason Brougham
Senior Principal Preparator
American Museum of Natural History
jaseb@amnh.org
(212) 496 3544