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




--- Tim Williams <twilliams_alpha@hotmail.com> wrote:

> A naked head is also useful for scavenging -
> prevents fouling of the plumage 
> while the scavenger is immersing itself in a rotting
> carcass.  I'm not 
> saying that _Archaeopteryx_ was a scavenger - but
> the head (and neck) may be 
> naked for purposes other than display.

In total, maybe 1% of living birds have bald heads.
Scavenging birds are much bigger than A., possibly
because carrion is scarce resource and they need
passive flight to cover vast areas to locate it. 

> As I understand it, this subhorizontal (~ parallel
> to backbone) orientation 
> of the femur in birds is associated with the
> position of the center of 
> mass/weight (CM) in modern birds. 

Agreed. Common assumption is that center of mass of A.
was further back than of modern birds because of bony
tail. However, front of A. was also more heavy,
including toothed jaws. So it might not be true. 

For CM in A. most important is size of sternum and
breast muscles and this is unknown and debated. So my
idea that examination of leg joints is needed to
decide it. 

I looked also at leg proportions of living mammals
(unfortunately, no long-tailed bipedial runner is
alive). Again, quadrupeds adapted for long-distance
running (canids, gazelles) have long tarsi, compared
to eg. cats and muntjac deer. This is probably because
long tarsus allows longer push before foot leaves
ground.

So I still maintain that A. was frequent walker but
not runner - more like a pigeon than roadrunner.

Jerzy Dyczkowski



                
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