Re: Archaeopteryx with bird book, was Re: Archaeopteryx flight

[Tim Williams <twilliams_alpha@hotmail.com>]

Jaime A. Headden wrote:

> Similarly, the feet of *Archaeopteryx* are suited to both a cursorial 
> function and a limited ability at grasping branches, thus scansorial.

According to Middleton, the feet of _Archaeopteryx_ have a very limited 
ability to grasp branches, to the extent that the toes were probably useless 
for this purpose.  The hallux was just too short and high on the foot.  
However, that does not necessarily mean that Archie didn't spend at last 
part of its time up in the trees.

Patrick Norton wrote:

> Your qualification is a good one.

I was trying to point out that vultures are specialist scavengers, but not 
obligate scavengers.  At least, this applies to those vulture species that 
do scavenge; as noted by Jaime and Jerczy, some vulture species are not 
scavengers (e.g., palm-nut vulture).

> Under those assumptions, we are still left with the facts that: 1) Archie 
> was small (relatively); 2) that views about its feeding behavior are almost 
> entirely speculative; 3) that there is no evidence for a selection towards 
> bald-headedness among extant small scavenging birds and that; 4) the 
> anatomy of birds can be expected to result in a  bias against the 
> fossilized preservation of contour feathers.

I would agree with all four.  I wasn't arguing that _Archaeopteryx_ was a 
specialist scavenger, but I do believe that the naked-ness of the head of 
modern vultures is associated with their delightfully disgusting method of 
scavenging upon large carcasses.

> Given all that, the simplest interpretation of the absence of preserved 
> head feathers on Archie is that it is exactly what would be expected in a 
> fossil bird, given the preservational conditions.

At least one specimen of _Microraptor_ shows feathers preserved on the head. 
 I take your point, though: the absence of a feathery head covering in 
_Archaeopteryx_ might be a preservational artifact.  But I think it is also 
possible that the absence of feathers from _Archaeopteryx_'s head might be 
real, and be associated with reasons other than scavenging.  I don't think 
we have enough evidence either way.  As a very primitive bird, we might not 
expect the head to be fully feathered (aside from the beak) as in modern 
birds.

Cheers

Tim