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

[Tim Williams <twilliams_alpha@hotmail.com>]

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.

Cheers

Tim