Re: vaulting pterosaur launch, questions

[dinoboygraphics@aol.com]

> > > Apart from bringing one back to life somehow, exactly how do we >> 
"properly" establish that Archie flew? The fossil evidence is entirely 
>> consistent with an animal that was most likely at least a 
rudimentary >> flapping flyer.

> > Actually, it's a bit mixed in this regard.

> Not very.

Sorry, but VERY.  In fact, that was the entire point of my post, that 
the popular image of Archaeopteryx is not consistent with the 
peer-reviewed literature.  For example, it's been observed that Archie 
did not have the shoulder mobility of a flapper:

Senter, P. (2006). Scapular orientation in theropods and basal birds 
and the origin of flapping flight. Acta Palaeontologica Polonica. 
51(2): 305â313.

It's been shown that Archaeopteryx lacked the ligamentous shoulder 
mechanism to stabilize the arm during flapping flight:

Baier, D. B., S. M. Gatesy, & F. A. Jenkins Jr. 2007. A critical 
ligamentous mechanism in the evolution of avian flight. Nature 
445:307-310.

It's been shown that Archaeopteryx lacks an ossified sternum:

Wellnhofer, P. & Tischlinger, H. (2004). Das "Brustbein" von 
Archaeopteryx bavarica Wellnhofer 1993 - eine Revision. Archaeopteryx. 
22: 3â15.


Where is the "entirely consistent with....a rudimentary flapping flyer" 
part?


Of course it's possible that these papers are wrong, or that 
Archaeopteryx used flapping flight in some manner very different from 
living birds, but that has to be established, not simply claimed.  It's 
also possible that Archaeopteryx represents some gliding part of the 
stem-avian tree, but of course the evidence is weak at best for true 
arboreal life (e.g. Mayr, G., Phol, B., Hartman, S. & Peters, D.S. 
2007, The tenth skeletal specimen of Archaeopteryx. Zoological Journal 
of the Linnean Society, 149, 97â116 ) and as Mike pointed out there has 
been serious discussion (with some evidence, I might add) that 
Archaeopteryx lacked the inboard wing:

Hartmann, S, Re-Evaluating Wing Shape in Archaeopteryx: Information 
from The Thermopolis Specimen. Journal of Vertebrate Plaeontology Vol 
27 suppl. no. 3, pg.87A

All of this casts grave doubt on the traditional image of Archaeopteryx 
as a tree-dweller gliding to the ground or from branch to branch, as 
well as it's ability to engage in flapping flight.  What Archaeopteryx 
did, and how, is very much an open question.  If you wish to falsify 
these findings that will be fantastic, but at least do the data the 
justice of testing it rather than simply ignoring it in favor of a long 
out-of-date popular image.


Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com


-----Original Message-----
From: ptnorton <ptnorton@suscom-maine.net>
To: mhabib5@jhmi.edu
Cc: dinoboygraphics@aol.com; twilliams_alpha@hotmail.com; 
dinosaur@usc.edu
Sent: Mon, 16 Jun 2008 5:16 pm
Subject: Re: vaulting pterosaur launch, questions


> > Apart from bringing one back to life somehow, exactly how do we >> 
"properly" establish that Archie flew? The fossil evidence is entirely 
>> consistent with an animal that was most likely at least a 
rudimentary >> flapping flyer.Â
> Â
> Actually, it's a bit mixed in this regard.Â
Â
Not very.Â
Â
> > How did it fly? By flapping its wings.Â
> Â
> Okay, very funny :) Seriously, though, there's a lot to this question 
of > importance: it includes launch, power output, flapping kinematic, 
and > landing dynamics.Â
Â
Seriously though, these questions are equally as valid for all flapping 
flyers, not just Archie.Â
Â
> > Why did it fly? Who the heck knows! You might as well ask why do we 
walk? >> Or why do fish swim?...Â
> Â
> I think Scott meant "why" as in "under what stimulus" - as a mode of 
> travel between elevated points, or as a predator escape, or something 
else > entirely?Â
Â
The correct question isn't "why" Archie flew, but under what conditions 
did flight became preferentially selected among pre-avian 
maniraptorans? Archie flew because it inherited the apparatus for 
flight from its ancestors. Why those ancestors developed that apparatus 
is an entirely different question.Â
Â
PTJN Â