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Re: Archaeopteryx skull redescribed and reconstructed



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.


Some recent studies have proposed that cranial kinesis is actually
basal for Paraves, but this trait was reversed independently in
certain basal avialans (see below) and derived deinonychosaurs.  For
example, the basal troodontid _Mei_ was interpreted as lacking a
postorbital-jugal contact, as well as having a weak nasal-frontal
articulation - both were cited in support of cranial kinesis (Xu and
Norell, 2004).  In light of _Archaeopteryx_, the evidence of cranial
kinesis (prokinesis) in some non-avialan paravians should perhaps be
revisited.


> It will be
> interesting to see how this impacts the phylogenetic placement of 
> Archaeopteryx
> relative to other deinonychosaurs and birds.


>From a phylogenetic perspective, the absence of cranial kinesis in
_Archaeopteryx_ actually simplifies things.  Basal avialans such as
_Confuciusornis_ and _Sapeornis_ have a robust postorbital-jugal bar
that precluded any involvement in cranial kinesis.  Thus, the
evolution of cranial kinesis would be a derived avialan character,
primitively absent in basal avialans.  (The cranial kinesis of
alvarezsaurs evolved independently of avialans - but this is the case
irrespective of whether _Archaeopteryx_ is a deinonychosaur or an
avialan.)


> My one problem is that I did a similar, albeit not identical, restoration
> in Dinos Air.


This theropod-like (akinetic) interpretation of the skull of
_Archaeopteryx_ was attacked by Feduccia in his 2003 review of
_Dinosaurs of the Air _.  Although I'd take anything written by
Feduccia with a huge dose of salt, it does demonstrate that the issue
of cranial kinesis in _Archaeopteryx_ is an incendiary subject.  This
is silly, because basal avialans like _Confuciusornis_ and _Sapeornis_
have essentially akinetic skulls.






Cheers

Tim