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Re: Bird arms
<< 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