The Scene of an Ancient Catastrophe - Walking On Eggs - page 21

gap in a small ridge, and through the gap, we caught a glimpse of the
badlands we were searching for. Fortunately, a small dirt road ran
through the gap, so we rumbled a mile or two down into the center
of the sunlit layers of ancient rock.
We parked the vehicle by the side of the road and turned the
crew loose to prospect the area for an hour or two. Most forays like this
are unsuccessful because few, if any, fossils are found, so we had no
great expectations. As we walked out onto the flats adjacent to the
beautifully banded layers of sandstone and mudstone, we scanned the
ground, searching for scraps of fossil bone. Within five minutes of
leaving the vehicles, we found ourselves walking across vast fields lit-
tered with dinosaur eggs. Acres and acres of reddish brown mudstone
were exposed on the flats, and every few steps, a cluster of broken eggs
lay perched on the surface. There were eggs everywhere, tens of thou-
sands of them. Although these had crumbled to pieces, the complete
eggs were clearly about a half foot in diameter, and the eggshell was
about one-tenth of an inch thick.
The first question, of course, was what kind of dinosaur had laid
those eggs? Paleontologists had often assumed that large eggs such as
these had belonged to the colossal sauropods. But we had worked in
the Gobi Desert of Mongolia with a crew that had discovered a meat-
eating Oviraptor embryo inside an egg that had previously been
thought to belong to a plant-eating Protoceratops. That discovery had
changed seventy years of accepted paleontologic wisdom and made us
cautious about prematurely identifying the kind of dinosaur that
had laid the eggs at our site. We did not want to misidentify the eggs
and create the kind of confusion that had surrounded the eggs from
the Gobi for so long.
We knew that sauropods had lived in this region of South America
near the end of the Mesozoic; we had found parts of their skeletons
just the day before in the outcrops of cemented sandstone and gravel
near Dona Dora's puesto. For more than a century paleontologists have
recognized that sauropod dinosaurs represent the largest land animals
ever known. Their names roll off the tongues of children and adults
alike, Apatosaurus (formerly Brontosaurus), Diplodocus, Brachiosaurus,
and so on. Adult remains of these animals have been collected on
numerous continents, but no skeletons of embryos inside their eggs
had ever been found. In fact, some paleontologists had speculated that