Geoscience Reference
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may have had an impact comparable to elephants in savannah ecosystems today, in
which dung beetles played an important role in the flux and flow of elements con-
sumed by such herbivores.
However, another mystery about the Two Medicine coprolites was how the
pieces of conifer wood had become so blackened. The answer came from within,
as in fossil bacteria that originally lived in
Maiasaura
guts. In a paper published
in 2001, geochemist Thomas Hollocher, Karen Chin, and two other colleagues de-
tected both abundant body fossils and chemical signatures of anaerobic bacteria in
the coprolites. These bacteria invaded vascular tissues in the wood and left distinct-
ive black organic residue called
kerogen
, the same mix of organic compounds in
oil shales. The simplest explanation for how these bacteria got into the plant tissues
is that they were in the dinosaurs' intestinal tracts. This made sense, as any mod-
ern herbivores likewise have gut microflora that aid in breaking down cellulose and
other compounds in consumed plants.
This discovery of bacteria that lived inside a dinosaur was important enough.
But the bacteria also did paleontologists a 75-million-year-old favor by helping to
fossilize the coprolites. Once these researchers examined thin sections of the cop-
rolites under microscopes, they realized that the calcite in the coprolites was prob-
ably precipitated in two stages: inside the vascular tissues of the fragments, then
in the areas between the fragments, including the dung-beetle burrows. They pro-
posedthatbacteriacouldhaveinitiatedthisprecipitation,startingwithlivebacterial
colonies in the original feces hardening these droppings. Once these proto-coprol-
ites were buried, calcification would have continued, turning what was originally
dark, mushy, and smelly into just dark and rocky.
Yet the story of these coprolites does not end with these two studies. As often
happens in paleontology and other sciences, this research raised more questions.
For instance, as Chin looked more closely at thin sections of the fossilized wood,
she realized that something was rotten in the Cretaceous. The hadrosaurs had not
been masochistically masticating hard, fresh, living conifers. Instead, they went for
