Re: I knew it!

["Tim Williams" <twilliams_alpha@hotmail.com>]

Greg Paul wrote:

> I've always been skeptical about this because it makes no functional sense 
> for animals that used their hands for manipulation to have such limited 
> lower arm and hand rotation.  [snip]
> Am very suspicious of arguments that this was true of any dinosaur, except 
> perhaps those with such reduced arms that it does not matter.

Another likely exception is the higher Maniraptora.  The manual digits of 
oviraptorosaurs and deinonychosaurs have a tendency to show reduced 
mobility, on account of (1) the locked interphalangeal joints and/or (2) the 
close appression of the proximal metacarpals.  (The oviraptorid _Heyuannia_ 
even shows some carpometacarpal fusion).

Thus, maniraptoran hands would have been capable of limited manipulation 
anyway.  The biomechanical studies of Gishlick indicate that deinonychosaurs 
could only grasp objects using both hands, and this may have been true for 
oviraptorosaurs as well.  There may have been an adaptive advantage to this 
inflexible manus (such as for grasping large prey, in the case of some 
deinonychosaurs), or it might be a relict of an ancestry among flying 
theropods.





Tim

_________________________________________________________________
The new MSN 8: advanced junk mail protection and 2 months FREE*  
http://join.msn.com/?page=features/junkmail