Re: Life of Birds (vertical running)

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

----- Original Message -----
From: "Tim Williams" <tijawi@hotmail.com>
Sent: Wednesday, October 10, 2001 10:45 PM


> I was referring to gross morphology.  _Archaeopteryx_ and _Rahonavis_
share
> more in common than any other bird.

I see.

> (Except perhaps that "Proornis" thing.)

Isn't that probably a confuciusornithid?

> >*Rahonavis* seems to have been the better secretary bird. [...]
>
> The secretary bird (_Sagittarius serpentarius_), like most (?all) extant
> birds of prey, has a pes designed for grasping and holding prey.  I don't
> think the pes of _Rahonavis_ is specialized for this purpose.  The
slashing
> claw of _Rahonavis_ may have been useful for *subduing* prey already
caught,
> but (as in _Archaeopteryx_) the pes seems to have had little utility in
> initially siezing the prey.  The flexor tubercles are very weak, and the
> hallux is too high.

True. Well, I think while the secretary bird catches its prey with a foot
and kills it with its beak AFAIK, *Rahonavis* is likely to have killed its
prey with its sickles claws immediately rather than catching it. Just
landing/stepping on the prey and <tchac>.

> This is the easy part.  The little chickadee is helped down by a
phenomenon
> known as "gravity".

So they simply jump down? Might an extensively fused sacrum/pelvis, as seen
in pygostylians (the more the closer to Neornithes), be required, or does it
just help?

> >Are there such steep dunes?
>
> "Steepness" may not have been the primary problem. [...]

I see. Thanks! :-)