Re: Archaeopteryx flight

["David Marjanovic" <david.marjanovic@gmx.at>]

----- Original Message -----
From: "Tracy L. Ford" <dino.hunter@home.com>


> -----Original Message-----
> From: Tim Williams
>
> >>By a "perching foot" I suppose you mean (in anisodactyl perchers) a pes
> that
> has a reversed and distal hallux that is opposable to the other three
digits
> allowing a greater degree of prehensile ability in order to grasp
branches.

yes

> A specialized perching foot allows a bird to adopt a vertical "hands-free"
> posture when sitting on a branch.  This is a very useful thing for a bird
to
> be able to do, since (with one notable exception) the anatomy of modern
> birds is entirely "hands-free".  At least in the sense that the digits on
> the manus are not free and useful for grasping.

(just to make sure -- the exceptions are hoatzin hatchlings?)

> Lack of a specialized perching foot would *not* prevent _Archaeopteryx_
from
> climbing trunks or branches, since it still had a mobile and fairly
> prehensile manus tipped with nice sharp claws.  Ditto for the pes, though
> this probably had less prehensile ability than the manus.<<
>
> Important point here, "hands-free". If they still used their hands while
> climbing then they wouldn't need a reversed hallux.

Well, phew. For sitting on a branch the long, opposed hallux which attaches
at the same level as the other toes seems indispensable; all basal
pygostylians including Confuciusornithidae have this feature,
*Archaeopteryx* (and *Microraptor*) _don't_. The former were arboreal...

BTW, the thumbs of birds _except hoatzin hatchlings_ are, like those of
*Archaeopteryx* and various basal deinonychosaurs, very short, which must
have impeding climbing IMHO.