Re: Archaeopteryx flight

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

David Marjanovic wrote:

> - lack of a perching foot, unlike *Confuciusornis* (and all basal
> Pygostylia);

In a lot of discussions on tree-living birds and theropods (of the non-avian 
variety) the terms "arboreal", "scansorial" and "perching" tend to get 
conflated.

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.  
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.

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.


> - apparent lack of high trees (is it possible that the few ginkgo trunks
> that are sometimes mentioned are driftwood?);

Even if these bits of ginkgo were driftwood (and I'm not saying that they 
were), then this implies the ginkgoes came from somewhere in the vicinity of 
_Archaeopteryx_'s watery graveyard - perhaps from a neighbouring island.  At 
any rate, there were trees of some sort within a radius capable of being 
reached by _Archaeopteryx_, even considering its weak flying abilities.


> - probable lack of sufficient flight abilities.

Explain to me why "probable lack of sufficient flight abilities" (whatever 
that means) implies that _Archaeopteryx_ couldn't climb trees?


Tim












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