Re: Sinosauropteryx at Dinofest

[Phillip Bigelow <bh162@scn.org>]

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.

Subaerial deposition, yes.  They're tasty to crows, ravens and
other ominvorous and carnivorous birds.  Also, because the
vitreous material inside the eyeball is 99% water, the eyes
show the first signs of dessication (usually rupture), provided (again)
that the deposition is subaerial.



>  So this
> interment must have completly covered the individual within that amount
> of time. 

Not necessarily, particularly in aqueous deposition (see below).



> 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)?

As a grouse hunter, I have done many anecdotal taphonomy experiments with
the amputated heads/necks of _Bonasa_. (start Frankenstein music here).

There are some small stagnant ponds (probably slightly anoxic, but not enough
to keep aquatic nematodes out) where I used to hunt. On a few occasions,
I put the articulated heads/necks of grouse on the bottom (surface of the 
substrate)
of these ponds, and checked them from time to time over a period of a few 
months.

After two months, all soft tissue (except a couple connective ligaments) had 
been
removed by critters of some sort (worms, I surmise).  I removed the remaining
material and found that the dark melanin pigment of the eyeballs had been 
retained in
the eye socket within the sclerotic rings.  All specimens showed this.

For some reason, the connective ligaments around the grouse cervical vertebrae 
were
completely gone, but the connective ligaments of the sclerotic rings were
still present and showed practically no signs of degradation.


Needless to say, when the Chinese photos were finally published, I was not
surprised to see dark pigmentation preserved within the eye sockets of
Sinosauropteryx.

The last issue of the journal _Palaios_ has a considerably more rigorous 
analysis of
what happens to bird corpses when they get deposited.  It is well worth a 
look-see.



Ref:

Davis, P.G. and Derek E.G. Briggs. 1998.
   The Impact of Decay and Disarticulation on the Preservation of Fossil Birds.
   PALAIOS, Volume 13, No. 1


Or go to this URL to read their abstract:

http://www.ngdc.noaa.gov/mgg/sepm/palaios/9802/davis.htm

                            <pb>