Geoscience Reference
In-Depth Information
ing, and the isotopic signatures in their coprolites were close to those of modern
plant-eating mammals. Furthermore, the nitrogen stable-isotope ratio matched that
of animals that do not use fermentation in their guts (usually aided by bacteria) to
helpdigesttheirfood.Soagain,thiswasmorelikebirdsandlesslikemammalsthat
use bacteria in their foreguts (small intestines) or hindguts (large intestines) to fer-
ment their food.
These geochemical clues gleaned from sauropod coprolites certainly gave pa-
leontologistsbetterinsightsonwhatthesedinosaursateandhowtheydigestedtheir
food.Yet,asmuchasichnologists hate toadmit it,theysometimes needafewbody
fossils in their trace fossils to better interpret the latter. So in 2005, Vandana Prasad
and four of his colleagues hit the jackpot, finding grass phytoliths in the same Late
Cretaceous coprolites from India studied by Ghosh and others.
Remember phytoliths? These are microscopic bits of silica precipitated by
plants and residing in their tissues, which also left microwear on dinosaur teeth
when they ate these plants. In many plants, phytoliths can be “fingerprints” for
identifying plant clades, and sometimes a specific species. Fortunately for dinosaur
ichnologists, phytoliths are also resistant to acids, so these can pass relatively un-
scathed through an animal's gastrointestinal tract. This evolutionary innovation by
plants thus helped earmark a minimum time for when grasses showed up in Meso-
zoicecosystems(65-70
mya
)aswellaswhendinosaursstartedgrazingorbrowsing
on them. Not mammals, but dinosaurs.
This discovery of grass phytoliths in sauropod coprolites thus fulfilled the
maxim of “You never know until you look,” especially when amended by saying
“You never know until you look in dinosaur feces,” or other trace fossils associated
with dinosaur digestion. From enterolites, to regurgitalites, to cololites, to coprol-
ites, which can beconnected togutbacteria, plants, snails, insects, mammals, birds,
and other dinosaurs, these trace fossils tell us inside stories and intimate details of
dinosaur lives.
