Re: Sinosauropteryx at Dinofest

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

Ralph Miller III wrote:
> 
> > Betty Cunningham <bettyc@flyinggoat.com> wrote:
> > Eyes are usually the first thing to be eaten by scavenging
> > invertebrates.  It's been my observation that eyes do not survive in
> > modern roadkills any longer than 24 hours after death.  So this
> > interment must have completly covered the individual within that amount
> > of time.  Is there signs of such a rapid interment?  Or alternatively,
> > are there signs all the scavenging invertebrates in the area were also
> > killed at the same time as the birds and dinos (leaving nothing left to
> > eat the eyes out)?
> 
> I can't positively answer that last question -- hopefully, someone else
> will -- but, given that the formation has been described in _Nature_ and
> _Discover_ magazines as a "Cretaceous Pompeii" which may have preserved
> nearly "a complete biota" such a scenario sounds plausible to me.  I read
> that the animals and plants may have been quickly killed by either
> poisonous gases or volcanic ashfall (or both).
> 
        The problem is that there isn't any real reason for these quotes 
in these high-flying magazines for volcanic-kills.  That is one of the 
things we are trying to get a handle on.  The Chinese have been saying it 
for a while now, but they have generated precious few data to support the 
notion (not that we have that much either, mind you).  There most 
certainly ARE tuffaceous and other volcano-clastic sediments in 
Liaoning.  If fact, the Yixian Formation is MOSTLY composed of these 
types of deposits, not the lacustrine rocks.  The problem is, I didn't 
see ANY volcano-clastics interbedded with the siltstones at Sihetun or 
anywhere else.  Overlying and underlying sure, but not WITHIN the actual 
fossil horizons.  
        If we had tuffs or something like that interbedded within the 
fossil beds, then I would be inclined to believe volcanic kills. The 
problem is, it is such a nice, neat, killing-mechanism that I WANT to 
believe it.  I am looking at the Sihetun sediments petrographically right 
now.  If there is something in the cements (I doubt we are going to see 
it in the clasts, but maybe) that suggests this mechanism, or if we can 
pull isotopes out of the fish bones we brought back, then MAYBE, just 
maybe, we might have some evidence for this mechanism.  I don't know yet 
(seems to be a common theme with this project...).  

        As for Betty's eye-eating hypothesis:  Are the roadkills you 
mention areal or subaqueous?  The two types of kills will have a much 
different taphonomic regime.  We DO have invertebrates preserved within 
the same sequences as the vertebrate fossils (they often pepper the slabs 
with the fish and birds).  However, we know very little about their modes 
of life.  Moreover, as I said before, there is no evidence for rapid 
deposition of these deposits.  Indeed, looking at the taphonomy of the 
critters and their remarkable preservational quality, I am forced to 
currently support the hypothesis that these are slow, aggredational 
assemblages.  

-- 
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Josh Smith
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