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These clutches contained no more than seven eggs, significantly
fewer than those at Auca Mahuevo. On average, the nests were about
two to three yards apart from one another within the clusters, although
the concentration of nests was not nearly as great as that discovered
in Patagonia. Originally, researchers thought that the eggs were laid in
depressions dug in the sand by the sauropods, but subsequent
researchers have argued that one cannot be certain of this because
there are no differences between the rock that entombs the eggs
and the rock that underlies the eggs.
Other, smaller exposures of the sandstone layer containing eggs
were found within a six-square-mile area surrounding the site. Based
on the density of eggs at the best site, Spanish paleontologists esti-
mated that up to three hundred thousand dinosaur eggs might be pre-
served in the red sandstone around the whole area. This led them to
speculate that the sauropods nested gregariously, but this conclusion
has been questioned by later studies of the eggs in this area. Other
palcontologic teams working in this rugged region of Spain have
identified several different layers of eggs that are similar in appearance
and microstructure. These field studies indicate that, as at Auca
Mahuevo, the alleged sauropods must have returned to the Spanish
nesting ground multiple times to lay their eggs.
The other area of the world that has produced numerous dinosaur
eggs in particular sites and many sites over a large region is in India.
Large, round eggs, found in clusters that might represent nests, are
preserved in rocks that formed near the very end of the Cretaceous
period. These rocks are exposed in a region referred to as the Deccan
Traps, a geologic province noted for its extensive lava flows that
cover the southwestern corner of India. As in the case of the Spanish
sites, the Indian eggs lack embryonic remains, but their large size has
made paleontologists believe they were laid by sauropod dinosaurs.
Some paleontologists have suggested that the large numbers of eggs
discovered in this region are evidence that these putative sauropods
returned to their nesting grounds multiple times. Although this is clear
at both Auca Mahuevo and the Spanish site, the egg-bearing layers
mixed in with the lava flows in the Deccan Traps are not as continu-
ous. This has complicated attempts to match up the egg-bearing strata
across the region and left some scientists skeptical about whether the
Indian dinosaurs returned to their nesting grounds multiple times.
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