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Re: Ostrich Wings Explain Mystery of Flightless Dinosaurs



Jura <pristichampsus@yahoo.com> wrote:

> The finding is neat, and I'm all for
> comparison with extant animals, but I wonder how pertinent
> it would actually be to dinosaurs. The paper seems to talk
> about ostriches using their wings for balance during agile
> maneuvers, but this is for a tailless animal. The theropods
> that gave rise to birds, all had nice long tails to do much
> of the counterbalance work. I'm just wondering if the
> results Schaller found might more accurately reflect an
> exaptation by ratites to a secondarily flightless existence,
> rather than a plesiomorphic behaviour. 


Yes, I wondered the exact same thing Jason.  Further, ratites are ornithurans, 
and so the center of mass further is shifted much further forward compared to 
the plesiomorphic theropod condition.  In ornithurans the femur is held in a 
mostly horizontal orientation, and is largely decoupled from terrestrial 
locomotion (stride generation).  So stride generation occurs at the distal 
femur (not the hip), and the "knee" is located between the tarsometatarsus and 
the tibiotarsus.


However, I understand that in ostriches the femur is actually used during 
running (but not during walking).  So the *entire* hindlimb is mobilized for 
stride generation when running.  This might add an element of instability 
during rapid maneuvers, which could require the wings to swing into action.  
None of these things would have been an issue for non-avian theropods though, 
in which stride generation occurred at the hip (acetabulum), and a hefty tail 
provided a counterbalance.




Cheers

Tim