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Re: Senter 2006, Confuciusornis, and humeral mobility

Jaime Headden <qi_leong@hotmail.com> wrote:

>   *Confuciusornis sanctus* has traits that are both intermediate as well as 
> unusual between these two group, including the reduced form of the second, 
> major digit and the giant deltopectoral crest and robust humerus;

Aside from _Confuciusornis_, a large, robust deltopectoral crest is
characteristic of several basal birds, including _Jeholornis_,
_Sapeornis_, and _Zhongjianornis_.  A large, robust deltopectoral
crest is lacking from enantiornithean and ornithuromorph (euornithean)
birds, which tend to have a longer sternum and larger keel.  According
to one hypothesis, a large deltopectoral crest in certain basal birds
at least partly compensated for the lack of an elongate, keeled
sternum.  The implication is that the prominent deltopectoral crest
offered an alternative strategy to power the wing during flapping
flight.  However, no supporting evidence was presented.  To my mind,
the large deltopectoral crest indicates that the forelimb was used for
some non-flight function, such as trunk-climbing.