Re: Quadruped theropods?

[Graydon <oak@uniserve.com>]

On Sun, May 21, 2006 at 04:27:30PM -0500, Tim Williams scripsit:
> Graydon wrote:
> >Birds did eventually find a way to get the forelimb involved in
> >locomotion again, but no quadrupedal stance.
> 
> One minor point, which doesn't really detract from your statement, which is 
> essentially correct given that no modern bird uses quadrupedal locomotion 
> when on land.  But the first birds (like _Archaeopteryx_, 
> confuciusornithids, and so forth) probably used all four limbs when 
> climbing trees.  Thus, they were arboreal quadrupeds and terrestrial 
> bipeds.  The same is probably true for microptorans and _Epidendrosaurus_.

Arboreally, they're suspended from, not supported by, the forelimb; I'm
not sure that counts as a quadrupedal stance, since they're not putting
a compressive load on the forelimb.

> Among modern birds, juvenile hoatzins are arboreal quadrupeds.
> Certain shearwater species have observed using their wings when
> climbing up tree trunks.

I've seen domestic ducks lever themselves out of the water trough with
their wings, too.  It's presumably still in the general behavioural
repetoire for the birds that aren't extremely specialized flyers.