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Re: More Bird origins: ignore if you wish...



GHO:

>"bipedality" itself is a cursorial adaptation--but it is a cursorial
>adaptation for lineages in which the forelimbs have become too modified to
>serve as portal locomotor organs.

Which could have occurred as the forearms became more adapted to grasp prey
- not necessarily for climbing, though this is certainly possible and
reasonable.

>Reduced forelimb size is also just such an adaptation, compensating for
>forelimbs that would have been much too big and too much in the way had they
>maintained their arboreal relative size in the cursorial forms (the forelimbs
>were reduced even in _Deinocheirus_; either that, or it was one odd-looking
>dino).

I thought Tom Holtz strated that forelimb size was NOT reduced in many
maniraptors.
>
>The trouble is, it is very difficult to separate cursorial adaptations of the
>kind described above from cursorial adaptations that would have arisen
>without an intervening arboreal stage.

Exactly.

 there would have
>been no retro-hallux.

Unless the retro-hallux evolved for prey capture.
>
>But this isn't even speculation anymore; it's speculation squared.

So is BCF as an ecological hypothesis.  BADD as I understand it is a
phylogenetic hypothesis - a quite different thing.

The point is that we have no way to prove arboreality - we can only suggest
it.  And as I said earlier this has nothing to do with phylogeny in the
strict sense.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
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