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RE: Vancleavea campi - what is it? - not an archosauriform.

  David, I am not sure what you mean about thalattosaurians, but thalattosaurus 
(from *Askeptosaurus* to *Dakosaurus*) possess both supratemporal fenestrae as 
well as antorbital fossa and fenestrae. The former feature makes thalattosaurs 
(if non paraphyletic) firmly ensconced with the diapsid condition, and 
therefore members of Diapsida. If, as previously argued, you think the diapsid 
condition cannot reverse to the anapsid condition, this should be pretty firm 
evidence for placement of thalattosaurs (again, if nonparaphyletic) within 
Diapsida (but don't take my word for it, read the Rieppel works instead). The 
latter feature is a common argument for archosauriform phylogeny, and does not 
seem to occur outside of it (based on the common occurance of crania with the 
fenestra to be found instead the structure assumed to be Archosauriformes by 
its definition).


Jaime A. Headden

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> Date: Fri, 4 Dec 2009 21:59:07 -0600
> From: davidpeters@att.net
> To: dinosaur@usc.edu
> Subject: Vancleavea campi - what is it? - not an archosauriform.
> One of the reasons why Vancleavea campi does not have an antorbital fenestra 
> and upper temporal fenestrae is because it is not an archosauriform. It is a 
> askeptosaurid thalattosaur and a sister taxon to the short-snouted 
> Miodentosaurus. [Links below]
> http://2007tga.cgu.org.tw/cdrom/Oral%20(PDF)/ST1-4B-06.pdf
> http://www.ivpp.ac.cn/cbw/gjzdwxb/xbwzxz/200902/W020090813372748918302.pdf
> The scales are still weird.
> The neomorph bone between the orbits is nothing more than the ascending 
> process of the premaxilla.
> For those who still think you have to stare at a specimen in person to 
> publish on it, well, now you see how that can prove to be a wee bit myopic.
> David Peters
> Refs:
> Cheng, Y.-N., X.-C. Wu, T. Sato. 2007. A new thalattosaurian (Reptilia: 
> Diapsida) from the Upper Triassic of Guizhou, China. Vert PalAsiatica 45: 
> 246-260.
> Nesbitt, S. J., M. R. Stocker, B. J. Small and A. Downs. 2009. The osteology 
> and relationships of Vancleavea campi (Reptilia: Archosauriformes). 
> Zoological Journal of the Linnaean Society 157, 814-864.
> Parker, W G. & Barton, B. J. 2008. New Information on the Upper Triassic 
> archosauriform Vancleavea campi based on new material from the Chinle 
> Formation of Arizona. Palaeontologia Electronica 11 (3); 14A: 20p.
> Wu, X.-C., Y.-N. Cheng, T. Sato and H.-Y. Shan. 2009. Miodentosaurus brevis 
> Cheng 2007 (Diapsida; Thalattosauria): Its postcranial skeleton and 
> phylogenetic relationships. Vertebrata PalAsiatica 47:1-20.
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