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Re: Coracoid/scapula (was Re: flying Archie)
Don Ohmes wrote:
If they go flightless, do they always lose the joint?
There's no hard-and-fast rule on this. Big flightless birds (like ratites)
tend to show coossification of the scapula and coracoid. But these guys
have been flightless for a long time, and the wings are pretty much
useless. One group, the dinornithids (moas), actually lost the forelimbs
completely. (Ernest Hemingway wrote a book about this: "Farewell to Arms".)
Birds that are recently flightless, and/or still use their forelimbs for
locomotion, tend to retain a mobile joint. Penguins do, and so do
flightless grebes, both of which use the wings in subaquatic locomotion.
David Marjanovic wrote:
Ah, then we aren't talking of exactly the same character. I am talking of
the joint, which I interpret as having 3 possible states: flat
(plesiomorphic), coracoid in scapula, or scapula in
coracoid. I may be wrong in which of these is the plesiomorphy, but the
reversals I mentioned all require independent losses of the joint.
But if the joint is closed, we don't know if any one of these characters is
reversed. The fusion blots the original character state out.