Geoscience Reference
In-Depth Information
CHAPTER
THIRTEEN
An Awesome Predator
Discovering a Skeleton
of the Sauropods' Adversary
One might think that being fifty feet long and weighing several tons
would make adult sauropods, such as those that lived around Auca
Mahuevo, quite invincible. But a pilgrimage to the nesting site at
Auca Mahuevo was clearly not without risks, even for giant sauropods
and their offspring. Fearsome predators roamed the floodplain.
During the first expedition to Auca Mahuevo, no skeletons of
adult dinosaurs were found at the nesting site despite several efforts
to find some. That we had found only a few fragments seemed quite
curious to us: With all of the eggs and embryos, why were there no
fossils of adults?
That all changed with Alberto Garrido's discovery of the large car-
nivorous-dinosaur skeleton that we described while recounting events
during the 1999 expedition. The portions of the skeleton that we had
uncovered showed that the new dinosaur was either a smaller version
of
Carnotaurus
or one of its close abelisaur relatives. We estimated
that it was about 70 percent as large as the only known skeleton of
Carnotaurus,
yet based on the structure of the bones, we knew defi-
nitely that it was an adult. A number of questions kept flying through
our minds as the long days of excavation passed. Could it simply rep-
resent a different sex than the other specimen of
Carnotaurus?
Could
it be a specimen of
Abelisaurus,
another abelisaur known only from a
skull that was collected from the same layers of rock about one hun-
dred miles away? Could it be a previously unknown species that was
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