Re: Archaeopteryx flight

["Tim Williams" <twilliams_alpha@hotmail.com>]

David Marjanovic wrote:

> The same figure shows anisodactyl
> (rather than, say, zygodactyl) feet on a hoatzin.

Yes, the hoatzin (_Opisthocomus hoazin_) has an anisodactyl pes, with the 
hallux pointed backward - unlike cuckoos (Cuculiformes) which can employ 
zygodactyl perching.

Incidentally, hoatzin chicks dive out of their nests to escape predation, 
into the water below - which hopefully lies underneath the nest.  Otherwise, 
splat.

To get back to the nest the young hoatzins use their beaks, necks and toes 
as well as their clawed fingers to clamber over twigs and branches.  I 
recall that somebody on this list mentioned that some adult hoatzins do 
re-grow their hand-claws.  Although the number of such individuals may vary 
from one hoatzin population to the next, one study showed a third of adult 
individuals had regained the claws that had earlier been shed; although in 
all these individuals the hand-claws were covered in callus and had no known 
function.

Hoatzins are weak fliers, but adult males do fight in the air - launching 
themselves at one another in rather bizarre mid-air collisions.


> But I still claim that the
> hands of hoatzin hatchlings are better suited to climbing than Archie's
> because they are composed of considerably thicker, more robust-looking 
> bones
> (including the unguals) -- Archie has very thin fingers actually.

In other words, _Archaeopteryx_ had nice long supple fingers for grabbing 
onto tree branches.


Tracy Ford wrote:

> People, people, the hallux is on the FOOT. The backward facing toe on 
> birds.
> It's not the hand.

I could be wrong (and I admit I do tend to read through messages rather too 
quickly), but I didn't pick up any recent posts which confused the two.




Tim

_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp