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Re: Archaeopteryx skull redescribed and reconstructed



Webmail here, I'm at a conference. 

Gesendet: Dienstag, 11. Juni 2013 um 05:45 Uhr
Von: "Tim Williams" <tijawi@gmail.com>

> GSPaul <GSP1954@aol.com> wrote:
>
> > The Rauhut paper is quite good. The demonstation of an articulation on the
> > jugal for the postorbital is particularly nicely done.
>
> Agreed. Further, Rauhut's interpretation that _Archaeopteryx_ lacked
> cranial kinesis is not just based on the strong postorbital-jugal
> contact, but also the inflexible contact between the nasal and
> frontal, which prevented the former sliding over the latter.

...which, in turn, would be majorly bizarre anyway. This is _not_ how extant 
birds achieve their prokinesis. Only parrots have an actual joint between the 
premaxillae and the frontals; in all other birds, the solid bone of the snout 
roof bends, because it's simply thin enough to do so. I have personally 
manipulated a swan skull and a heron skull that were apparently fresh enough to 
allow this (when the bone dries out or whatever, it does become hard at some 
point). All the sutures are immobile, none of them acts as a joint, a large 
area of solid bone bends. This is, BTW, quite different from the mesokinesis 
observed in most squamates, where the frontal/parietal suture is completely 
straight and acts as a hinge.

As far as I can tell, every kind of skull kinesis observed in any extant 
vertebrates (yes, including mesokinesis, complete with a "sliding joint" 
between postorbital and jugal...) and then some have been proposed for 
*Archaeopteryx* at some point. Some attempts looked really desperate, along the 
lines of "but it's not a mammal or a turtle or a crocodile, it just _has_ to 
bend somewhere". I think this comes from treating some squamate archetype as 
the default "reptile": default reptiles have skull kinesis, birds have skull 
kinesis, so logically Archie must have had skull kinesis, somewhere, somehow...

It's not just Archie. Don't get me started on, say, gorgonopsians or 
anthracosaurs. Or just remember pleurokinesis.