Re: Hone and Benton 2007 (their second paper)

[Tim Williams <twilliams_alpha@hotmail.com>]

Michael Habib wrote:

> In addition, the build and mechanics of most pterosaurs are not set up such 
> that they would gain a great deal by bipedal locomotion (as best I can 
> tell, in any case).

I'm not presenting this as either "pro" or "con", but merely because it's 
out there, and it <might> be relevant...

There was one study that found that the curvature of pterosaur toe claws 
tended to be similar to the claws of walking or wading birds.  By contrast, 
the claws on the wings were curved like the toe claws of birds that use 
their feet for grasping or perching.  Rather than suggesting arboreality in 
pterosaurs, the hypothesis was that pterosaurs walked bipedally but used 
their wing claws to grasp prey while it was being chomped on by the jaws.  I 
don't know if this study has been published yet, but it did form the basis 
of a thesis (Atreyee Gupta) and an SVP presentation (David Krauss).  (I 
don't know if the study took the keratinous sheath into account.)

> Just because we cannot see the benefit does not mean it did not exist, but 
> it does make me more skeptical of the concept of bipedal progression in 
> pterosaurs as a common means of transport.  The fact that the 
> interphalangeal lines do not preclude bipedality in pterosaurs is useful to 
> know, but I suspect it is not a result of bipedal running.

Yes, I agree.  On my earlier point, I would say that adopting a bipedal 
stance for handling prey is separate from bipedal progression per se.  
Although there's nothing to suggest that pterosaurs couldn't walk and eat at 
the same time.

Cheers

Tim


I doubt that bipedal running would
> be faster for them, and quadrapedal launching would be more powerful (and 
> is supported by several aspects of morphology, especially in larger 
> pterosaurs).  Just because we cannot see the benefit does not mean it did 
> not exist, but it does make me more skeptical of the concept of bipedal 
> progression in pterosaurs as a common means of transport.  The fact that 
> the interphalangeal lines do not preclude bipedality in pterosaurs is 
> useful to know, but I suspect it is not a result of bipedal running.
>
> Cheers,
>
> --Mike H.

_________________________________________________________________
Catch suspicious messages before you open them?with Windows Live Hotmail. 
http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_migration_HM_mini_protection_0507