Re: Placement of Segnosauria (was Re: Details on Nanshiungosaurus bohlini)

["Timothy Williams" <twilliams_alpha@hotmail.com>]

David Marjanovic wrote:


> Sad to say, I don't know most of these studies, not even their refs. My 
> arguments for putting Segnosauria into Plateosauria (sensu Sereno: 
> Massospondylus + Plateosaurus) are:

(a) and (b) refer to the association of the _Beipiaosaurus_ type material.  
There's nothing that suggests to me that the material is chimeric.

>   c.. There is this 11 cm long segnosaur dentary from the Early Jurassic 
> of Lufeng. AFAIK, it shows evidence for cheeks (suggested for prosauropods, 
> unknown in any theropods): Zhao Xijin & Xu Xing: The oldest coelurosaurian 
> [sic], Nature 394, 234f. (16 July 1998)

I think there are doubts over whether this dentary (IVPP V11579) really 
belongs to a therizinosaur.  It may actually come from a prosauropod (maybe 
_Lufengosaurus_).  This may have been discussed previously on this list.

>   d.. A beak at the front of the jaw has been suggested for e. g. 
> Massospondylus.

The presence of a "beak" in _Massospondylus_ was suggested by Crompton and 
Attridge (1986) on the basis of a _Massospondylus_ skull from North America 
(MCZ 8893); they say that the tip of the lower jaw may have been covered by 
a horny sheath.  This is refuted by Gow et al. (1990), who rejects the 
interpretation that _Massospondylus_ had a beak.

See:
Attridge, J., Crompton, A.W., and Jenkins, F.A., Jr (1985).  The southern 
African Liassic prosauropod Massospondylus discovered in North America.  J. 
Vert. Paleontol. 5: 128-132.

Gow, C.E., Kitching, J.W., and Raath, M.A. (1990).  Skulls of the 
prosauropod dinosaur Massospondylus carinatus Owen in the collections of the 
Bernard Price Insitute for Palaeontological Research.  Palaeont. Afr. 27: 
45-58.

Can't comment on (d) and (e).

>   f.. Oviraptorosaurs and segnosaurs *look* very different; this might of 
> course change with the discovery of more fossils, but judging from the 
> present material...

Evolution happens.  What more can I say?



Tim


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