Geoscience Reference
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vating a large quarry near the embryo site and mapping the position
of each egg that was found there. We anticipated that this would give
us a good idea about whether individual eggs were arranged in clusters
that might represent nests or whether the sauropods had laid the eggs
more randomly across the surface of the floodplain without con-
structing or utilizing distinct nests. Some evidence from other sites
suggests that sauropods did the latter. At a site in southern France, for
example, large eggs long thought to belong to sauropods appear to be
laid in large semicircles without any indication that they were clustered
in nests. At main other sites, megaloolithid eggs—the kind of eggs
typically attributed to sauropods—have been found in more scattered
patterns rather than in discrete clusters.
Frankie Jackson was instrumental in our egg-mapping at Auca
Mahuevo. With the experience she had mapping dinosaur eggs in
Montana, we knew that she should be the one to record the position
of each egg in three dimensions. Our team surveyed the area within
the quarry and laid out a system of one-meter squares, much as is
done in an archaeological excavation. The initial quarry excavation
covered twenty-five square meters, slightly more than twenty-five
square yards. As new eggs were exposed during our excavation,
Frankie would record their horizontal distances along the sides of
the gridded rectangle from one corner of the quarry. We also
recorded the elevation of each egg in the quarry with respect to a
fixed point. The positions of more than two hundred whole eggs
were eventually mapped, far more than in any other previous study.
After gathering the data, Frankie analyzed the maps back in the
United States using a variety of statistical methods. To help her in
these analyses, she recruited Richard Aspinall, a computer scientist at
Montana State University in Bozeman. Frankie and Richard pro-
duced a three-dimensional map of our quarry that could be rotated
and viewed from the top, the sides, and any other angle. The analyses
showed the eggs were definitely clustered, not randomly distributed,
although some eggs lav scattered between the more well-defined
clusters, suggesting that the clutches may have been laid in nests of
irregular shape. At least nine clusters were documented, and seven of
those contained between fifteen and thirty-four eggs. This suggested
that individual sauropods had laid clutches of eggs during one sitting.
Given the way streams flow, we could not envision how currents dur-
