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Re: Origin of bird flight: ontogenetic-transitional wing (OTW) hypothesis



"Although I don't necessarily agree with everything in the paper (only ~ 
90-95%).  For example, I'm a bit skeptical about this...

"Commonly held assumptions within the cursorial school about the plausible 
function of proto-wings are inconsistent with the ontogenetic biology of extant 
forms; for example, no extant species uses its wings to run faster, to secure 
prey or run–glide."

No extant avian uses its forelimbs to catch prey, because these forms already 
have the forelimbs highly modified into wings; or else they are flightless 
birds that evolved from forms that had the forelimbs highly modified into 
wings."

--Good point.  I remain skeptical of the applicability of their model to basal 
birds.  The authors assert that the model is analogous because the juveniles 
have relatively undeveloped wings, but the model taxa are still gallanaceous 
birds, which are burst launch specialists.  I wonder if the relatively well 
enlarged pectoralis fraction, with large amounts of anaerobic power, and the 
very rapid upstroke of burst launch specialists comes into play with regards to 
the incline running and similar behaviors.  To be convinced, I'd like to see 
more information on the muscle power, and upstroke activity of the juvenile 
birds.  Based on the data and videos available so far, it seems as if a rapid 
upstroke is important to the observed behavior.  Considering that basal birds 
had a deltoideus-driven upstroke, and possibly less humeral elevation than 
modern taxa, it may be that the incline-running type mechanics were unavailable 
to them.

Cheers,

--Mike H.


Michael Habib, M.S.
PhD. Candidate
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181
habib@jhmi.edu