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Re: Placement of Segnosauria (was Re: Details on Nanshiungosaurus bohlini)
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.
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.
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:
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
Evolution happens. What more can I say?
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