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Re: Coracoid/scapula (was Re: flying Archie)

David Marjanovic wrote:

I don't think it is primitive. ?Within Enantiornithes itself, *Protopteryx* has a flat joint (no peg, no socket). I forgot about *Jibeinia*. The confuciusornithids have fused scapulocoracoids, and *Sapeornis* has a suture (which would possibly have fused with age)... That makes 3: the assumption of convergence is more parsimonious than that of several reversals.

I'm not sure what you mean here. What "convergence" are you referring to?

How about this scenario.... the immobile scapulacoracoid is primitive, but enantiornithines and euornithines evolved peg-and-socket articulations independently (athough with opposite configurations); and the flat joint is an intermediate step between the immobile joint and the peg-and-socket joint.

Some modern bird species (representing galliforms and paleognaths) show a flat joint too.