Re: The Lake Psittacosaurs

[smithjb@sas.upenn.edu (Joshua Smith)]

tlford@ix.netcom.com wrote:
> 
> > 
> > PSITTACOSAURUS FROM THE LAKE
> > 
> > Greg Paul notes that Ji has said that there are psittacosaurs found in the
> > lake with scaly skin (darn!).  Does anyone know where these are to be
> > published, if at all, and does anyone have any idea which of the 7 or 8 
> > valid
> > psittacosaur species these might be?  I know that Psittacosaurus 
> > mongoliensis
> > and P meileyingensis are found in Liaonang Provence.  Are they one of these?
> > If they are P mongoliensis, then the age of the Yixian Formation is almost
> > certainly Early Cretaceous, rather than Late Jurassic as it is unlikely that
> > either species lasted more than 20 or 25 million years.
> > 
        I don't think that the verdict was out as of August 97 for which 
spp. of _Psittacosaurus_ those specimens are.  The stuff coming out of 
the Juifotang Formation, which overlies the Yixian and is the one where 
the majority of the psittacosaur material is found (enough so that I 
would almost believe terrestrial, vertebrate biostratigraphy if it were 
done here...) is _P. mongoliensis_ for the most part.  The Juifotang is 
pretty likely Berramian in age.

> 
> I have seen, photographed, video taped and drawn 3 specimens from THE
> LAKE. One had a really good skull with premaxillary fangs, but now feet
> and tail was missing. The others weren't that well preserved. Some did
> have skin impressions. The first specimen I noted that and asked the
> 'owner' of it and he said now, but the last one he said that it that one
> had skin impressions, the same as the first. 
> 
        THE LAKE.  What does that mean?  Why does everyone keep calling 
it THE lake?!  Which lake?  Are you sure it was one lake, even at 
Sihetun?  Damn, I wish we had that kind of temporal resolution and 
control on the sedimentation...

        Hmmmm...the Yixian psittacosaurs I saw were not in lacustrine 
rocks.  They were in lake margin rocks.  and they didn't come from 
Sihetun (though very close).  I know this might sound like we are 
splitting hairs here.  Lacustrine rocks--lake margin sediments. So what? 
Well, let's just think for a minute about this ridiculus hypothesis that 
was circulated last year at SVP about the "sub-aquatic" habits of 
_Sinosauropteryx_.  Whether or not the specimens of _Sinosauropteryx_ had 
come from lacustrine sediments or say, fluvial overbanks (which can look 
just like lake margin rocks in the right environment...) might have been 
a nice point to have to refute or support that hypothesis, no?


-- 
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Josh Smith
Department of Geology
University of Pennsylvania
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