[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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.

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