Geoscience Reference
In-Depth Information
a fermented form, like barley, oats, or hops. With regard to the latter, paleontology,
geology, and many other sciences could not be done without these grasses and their
by-products, or at least these sciences would be a lot less fun.
The conventional wisdom about grasses is that they first evolved from non-
grassy flowering plants during the Cenozoic Era—in just the past 65 million
years—and especially took off in just the past 30 million years or so, first in South
America, then in North America. Grazing mammals, including the earliest horses,
were always thought to have facilitated the spread ofamber waves ofgrain. Indeed,
changesinhorsedentitionandlimbswerelikelylinkedtochangesingrasslandhab-
itats over time. Dinosaurs, in contrast, had absolutely no place whatsoever in this
comforting story of co-evolution between grasses and mammals. Having all van-
ished soon after a big rock arrived 65
mya
, non-avian dinosaurs only contributed
their recycled elements to the soils feeding grasses, with their bones ground to dust
under the hooves of grass-grazing ungulates.
Fortunately, thanks to some Late Cretaceous sauropod coprolites from India,
we now know this story needs updating. Two studies, done in 2003 and 2005,
showed that sauropods—specifically,titanosaurs—were eating different plants than
expected, andthelatter studyrevealed thattheseplantsincluded grasses.Theseres-
ults surprised nearly everyone for two reasons: few people suspected that grasses
had evolved during the Mesozoic, and almost no one expected to find fossils of
them in dinosaur coprolites.
Thefirstdetailed reportonthesecoproliteswasbyProsenjitGhoshandfiveof
his colleagues in 2003. How did they know these coprolites came from sauropods?
First of all, these grayish masses in the Lameta Formation of central India were
actually first identified as dinosaur coprolites in 1939. Their makers were then de-
duced on their occurring in the same strata as titanosaur bones. Moreover, although
they were not very large by titanosaur standards—the biggest were only about 10
cm (4 in) wide—they were big enough not to have come from any other herbivor-
ous animal in those strata. The researchers also noted how the coprolites had dried
