[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Science feather strength debate
> > If the tail was also generating lift, could it have
> > partially compensated for a lack of tertials?
Without doing any sort of complicated analysis: I'd say as far as descent rate
and stall speed - yes, but as far as L/D goes - it would only make things worse.
> And further, could the inboard wing gaps have actually
> 'energetic air' the tail could harvest?
I doubt it.
I'd be more inclined to believe they tertials just weren't attached as well, or
something else that leads to just a preservation artifact.
Otherwise, it seems like Microraptor would have a more bird like wing than
Archie, which is odd (though this is hardly an argument against the
I would also point out that if the wings tapered smoothly from narrow at the
shoulder, to a wide chord at the manus, that one wouldn't get something like a
pronounced tip vortex like what one finds at the tips of bird wings in flight
Ie, if the wing were shaped like in this reconstruction anchiornis:
I doubt the inner wing would make much of a vortex, making the tail even less
likely to be there to recapture that energy.
I can also engage in pure speculation: what if there was a flap of skin going
to the elbow - like some sort of hybrid between birds an pterosaurs (not an
evolutionary hybrid, but a morphological hybrid).
Suppose forearm and manus feathers were there for some other purpose, and when
parachuting/gliding started, as has happened many times, a flap of skin
developed - going only to the elbow, that receded as feather range expanded.
I've also watch squirrels and lizards go scampering down steep ravines/ the
steep terrain flanking creeks and water drainage channels when riding past them
in the CA bay area hills.
The birds, ranging in size from very small, to fairly large turkeys, often just
launch themselves and glide to the other side of the creek.
The non-gliding animals can't flee as fast - running downhill on uneven terrain
is tricky - particularly for some weight distributions (I've heard it said one
actually stands a chance of outrunning a bear going down a steep hill, whereas
going uphill just means you die tired.)
Wings could have started as aerodynamic stabilizers to aid in running down
hill- which I suppose could work and be beneficial if it involved less change
than return to a quadrupedal stance.
And it would result in coupling proto wings (that are not sufficient for even
gliding) with well developed legs and no arboreal adaptations.
The biggest question that I see is: How viable is a "small animal that runs
downhill well" niche?
IMO, as I've said before, once you get an animal that can glide and get a
decent L/D, all you need is for its geographical range to intersect an area of
favorable weather long enough, and the path to flight becomes trivial.
I'm most interested in how these forearm feathers got started, not how they
were used once it seems gliding was possible.