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



This is all really cool stuff about _Archaeopteryx.  The fundamental
questions asked following its discovery still lack a definitive answer.  Is
it an avian dinosaur or a non-avian dinosaur with wings?

Do the analysis done recently code wings and feathers as characters?  As
this would have to be coded as unknown for most dinosaurs, it seems of
limited value but I am not an expert.

I go for the winged dinosaur myself and it may answer another of those
perennial questions, what were T.rex arms for - to put its wings on!

John Hunt

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu] On Behalf Of
Tim Williams
Sent: 25 October 2005 21:44
To: dinosaur@usc.edu
Subject: Re: Archaeopteryx with bird book, was Re: Archaeopteryx flight

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