RE: Cost in Aquatic Birds (the big one)

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

David Marjanovic wrote:

> Hm. I have paintings of *Galago crassicaudata* (aka *Otolemur
> crassicaudatus*) and *Galago senegalensis* in front of me. [snip] Both 
> have relatively longer tails, especially *G. senegalensis*. Both have
> considerably shorter arms than *Sinornithosaurus* (in relation to
> hindlimb length). At least *G. crassicaudata* has fully opposable 
> halluces and pollices, unlike *Sinornithosaurus*. 

I finally reached the end of this message.  Dave, I've read Tom Clancy
novels shorter than some of your posts.    :-)

Anyway, I agree with David on this one.  The lack of an effective grasping
manus and pes in non-avian theropods is the strongest argument against
leaping from branch to branch.  Add to that, the restricted mobility of the
entire forelimb.


Jaime Headden wrote:

>  I don't see this as a problem. One simply turns the animal 90 degrees 
> and have it run along the branch. The arms serve as stabilizers. 
> Trunk-landing and bush landing need never involve so much as a grasping 
> hold, but a spread of the arms into the brush. 

Running along a branch, without the benefit of an opposable hallux?  Seems a
little tricky to me.

>  Indeed they don't. I do not suggest brachiation at all, but more of a 
> "flying-squirrel" analogy, something plausible at least for the smaller 
> animals like *Microraptor*, 

On this point, you may be interested to know that the Japanese flying
squirrel (_Petaurista leucogenys_) has very inflexible fingers and toes, and
is poorly adapted to gripping branches - unlike other flying squirrels on
all accounts.  Although extremely clumsy when clambering around branches,
the Japanses flying squirrel climbs up tree trunks extremely well.  


Tim


References

Ando, M. and Shiraishi, S. (1991).  Arboreal quadrupedalism and gliding
adaptations in the Japnanese flying squirrel _Petaurista leucogenys_.
Honyurui Kakgaku 30 (2): 167-182.



------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163 

  
 





Both have much more mobile arms and
hands than any dinosaur. Both have directly forward-facing eyes, unlike
*Sinornithosaurus* (and AFAIK still much more so than *Tyrannosaurus*).