Re: dinodimorphism

["Jaime A. Headden" <qilongia@yahoo.com>]

Nick Longrich (longrich@alumni.princeton.edu) wrote:

<<There's a way- eggs found inside a gracile or robust morphotype would pretty 
clearly demonstrate
that one of the morphs was female.>>

and Mike Keesey (tmk@dinosauricon.com) wrote:
 
<Hmm... are there any telling differences between the two known specimens of 
adult
_Sinosauropteryx prima_? (Of course they could both be female ... or it could 
be a species without
much dimorphism ... guess we need more specimens.)>

  While notable and at first indicative of a true gender for a dinosaur 
specimen, the apparent
eggs in the abdomen of one specimen does not appear to indicate the actual 
gender of this
specimen. The eggs are in a ventral and anterior position in the gastric 
cavity, and are not in a
position near which female vertebrates keep their oviducts (dorsally and near 
the ilia, around the
posteriormost dorsal centra). So this animal may 1) have displaced eggs ready 
to be laid or 2)
have swallowed eggs. Study of these eggs (?) are in prep per Currie & Chen 
(2001). See my recent
post on *Sinosauropteryx.*

  Also in the same issue of _CJES_ is a paper by Xu and Zhang on the cranial 
anatomy of
*Sinornithosaurus*, including two interesting qualities. One, there is, in prep 
from an analysis
of one of the species themselves, the suggestion that the earliest 
dromaeosaurids were the most
birdlike, and that the most derived were not. This shortens the expected length 
of variation
between the dromaeosaurids and the birds (Xu et al., 1999b). Two, there is one 
unexpected cranial
autapomorphy of *Sinornithosaurus*, lingual striae on the premaxillary and 
mesial dentary crowns,
convergent with *Ceratosaurus* and *Masiakasaurus* (both are neoceratosaurs). 
Cool stuff.

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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