Re: Bird arms

[RaptorRKC@aol.com]

<< Something to do with Dollo's Theory / Rule / Tendency, which states that 
 organisms cannot re-evolve adaptations once they are lost.
 
 Alvarezsaurids have truncated, coossified forelimb bones because they 
 evolved from volant birds which had a fused carpometacarpus.  A fused 
 carpometacarpus is (presumably) useless for predation, but it may have been 
 co-apted as a digging instrument by alvarezsaurids. >>

A lot of this stuff rings a bell.  The reason I brought up this evolutionary
tendency in flightless avians towards brachial vestigialism is because of one
group that seems to have "broken" the rules: the phorusrhacids.

As far as I know, they managed to "re-evolve" functional manual digits and
turn their flight apparatus back into a "normal" arm.  That phorusrhacids
managed to achieve this is why I was wondering other flightless birds did not
as well.

Rachel Clark