[Rockhounds] Coprolites

[Rock Currier]

At the Tucson show we bought a bunch of 'crorolites' from Madagascar and
because we had so many customers ask about what they were, I did a bit of
research on the net and the best thing I found written about them was 'A
Fresh Look at Sideritic 'Coprolites' by Adolf Seilacher, Cynthia Marshall,
H. Catherine Skinner and Takanobu Tsuihiji in the Journal of Paleobiology,
Vol 27, No.1 (Winter 2001) pages 7-13. I even paid $12 to down load the
article. The authors believe that 'coprolites' are the fosilized remains of
the intestinal tracts of dead amimals. The authors observe  that fresh
animal dropings are commonly pointed at one end only and invite any doubters
to watch a dog deficate. They also point out that the striations observed on
the 'coprolites' are very much like those one might expect would be fromed
by the mussel bands observed in the intesteines of many animals. The authors
conclude:

1. On morphological grounds we claim that twisted sideritic 'coprolites'
from fluvial deposites of avrious ages are intestinal casts (colonites). In
the very special microinvironment of the gut, good contents must have become
mineralized immediately after death- presumably by the bacteria already
present.
2. Since no other vertebrate remains are preserved in the beds conaining
these fossils another diagenic event must have wiped out the phosphatic
bones and teeth and transformed the premineralized gut contents into
siderite. Groundwater roll-fronts provide a possible mechanism.
3. These preliminary findings call for more systematic excavations and
actuopaleontological, sedimentological and geochemical studies of this
remarkable taphofacies.

Sideric colonites convey an important general message. It is clear that an
intestinal cast can form only after death: a rare case indeed compared to
the thousands of droppings some indifidual has produced during its life
time, Yet, taphonomy is a scinece of the rare cases, because in geological
time organismic remains adccumulate not according to orginal numbers, but in
proportion to their relative fossilization potentials, where the rare event
may become the common occurrence.'

Rock