Re: Placement of Segnosauria

["David Marjanovic" <david.marjanovic@gmx.at>]

> >   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.

I'll look for that in the archives. Of course, the age and associated fauna
make it suspect, but as written in the original paper:

"Figure 1 The left mandible of the specimen (V11579). a, Medial view. The
downturned dentary and numerous small teeth are shared with
therizinosauroids and a few other coelurosaurian theropods (troodontids and
ornithomimosaurians), whereas the posterior decrease in size of the teeth
and the morphology of the teeth are unique to therizinosauroids. b, The
dorsal view shows a lateral shelf on the dentary. This is also present in
ornithischians but is never so broad and flat as in this specimen and
therizinosauroids. c, Tooth crown in lateral view. The tooth morphology,
although superficially similar to that of some ornithischians and basal
sauropodomorphs, is also unique to therizinosauroids in its combination of a
basal constriction, circular roots, and lanceolate crown. bc, basal
constriction; d, dentary; ip, interdental plate [does the presence of
interdental plates say something about taxonomy?]; mg, meckelian groove; nf,
nutrient foramina; sp, splenial."
"The therizinosauroid affinities of the specimen are indicated by the
presence of a broad and flat shelf lateral to the tooth row and the few,
large nutrient foramina below it; the downturned anterior end of the
dentary; the decrease in size of teeth posteriorly; the large number and
small size of the teeth; and the morphology of the teeth (Fig. 1)."

Most will have the paper; I can send a scan.

Maybe Xu Xing's own e-mail address (given in the article, could be outdated)
will help: xxu@sun.midwest.com.cn

P. S.: Please, everyone, stop mailing answers to me _and_ the list -- I all
get them twice.