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RE: Senter 2006, Confuciusornis, and humeral mobility



  Although I meant to reply sooner, Tim Williams beat me on at least one thing 
I wanted to say, and Mike Habib on another. Suffice it to say, I do not think 
the nature of WAIR is a clear indicator of incipient arboreality and pre-flight 
evolution in birds as it has been suggested by some; nor do I think 
*Confuciusornis sanctus* has all that much to do with shearwaters.

  As I said, the ecology of the former is very different from the latter, and I 
find myself wondering at some other exaptive purpose for long, thin wings when 
flight ability is removed from the equation. I am not arguing flight is NOT 
POSSIBLE, but that it shouldn't be precluded in the issue. Both antecedents and 
decendents in the Avialae to *Confuciusornis sanctus* have stubbier, 
lower-aspect, and rounder wings, and longer tails, more distinct retricial 
arrays (or whatever term is suitable for *Archaeopteryx lithographica*) and 
very divergent arm, shoulder and pelvic anatomy.

  1. On the one side, picking *Archaeopteryx lithographica,* and assume we're 
just using the London specimen, you have a taxon with no ossified sternum, an 
open scapulocoracoid joint, a long bony, stiff tail, no alula, and questionable 
arboreality in the morphology of the pedal apparatus ("pamprodactyl" pes, short 
and proximal hallux), on top of a nearly vertical or marginally inclined pubis 
(and thus a deep, vertical ovate body).

  2. On the other side, picking *Iberomesornis romerali* here, we have a large, 
keeled and ossified sternum, closed scapulocoracoid joint, a short series of 
uropygals surmounted by a large pygostyle, likely an alula if it's any similar 
to other enants with better preservation, almost certainly a derived grasping 
pes with arboreality being likely due to the distal and very large reversed 
hallux (anisodactyl pes), and a reflexed and shallow pubic profile, and thus a 
shallow body section.

  *Confuciusornis sanctus* has traits that are both intermediate as well as 
unusual between these two group, including the reduced form of the second, 
major digit and the giant deltopectoral crest and robust humerus; it also has 
many "derived" traits, such as a reflexed pubis, pygostyle, distally located 
hallux, likely anisodactyl arrangement of the toes; but some other "basal" 
traits, such as a small sternum, small keel, no alula. None of the 
flight-evolving issues allow us to figure out why an apodiform-like wing aspect 
is occurring in a forest-dwelling, lacustrine bird, in which the advantages 
such a wing grants are not necessarily exploitable. Now, maybe I'm wrong here, 
but I'm thinking that the advantages of the wing can be had elsewhere, 
including a variety of non-locomotory ways, or secondary rather than primary 
locomotory functions, such as balance while running, display, or a host of 
other things such as the Hopp-Orsen Hypothesis (wing-brooding).

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)





----------------------------------------
> Date: Sat, 26 Mar 2011 09:26:20 -0400
> Subject: RE: Senter 2006, Confuciusornis, and humeral mobility
> From: jaseb@amnh.org
> To: qi_leong@hotmail.com
> CC: jaseb@amnh.org; dinosaur@usc.edu
>
> Mr. Headden,
>
> 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?
>
> Other birds with very pointed wings that inhabit inland bodies of water in
> forests include the Wood Sandpiper, Curlews, and Common Snipe.
>
> >   These birds do not suffer... the absence of an alula (for landing
> >controls)
>
> True, and that should be kept in mind. Yet Confuciusornis DID retain a
> jointed wing finger which opens the possibility that it could modify the
> configurations of its primaries, thus radcally changing the shape of the
> wingtip (possibly even rolling it up and/or cupping it). The motions of
> the fingers are crucial in the flight of bats.
>
> I was surprised to see such a textbook case of Wing Assisted Incline
> Running in those Shearwaters. Over and over I am taught the lesson that
> one can perpetually argue over what is possible or impossible for an
> animal to do, and then one film of a real animal can wipe out all of that
> reasoning in a moment. That may be my bias, since Carl Gans was my first
> mentor, and he spent his career trying to measure and record what diapsids
> could do in the lab.
>
> -Jason
>