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looks more like the knobby skin of Gila monsters than that of typical
lizards. Folds in the skin on our embryos indicated that the skin was
not closely attached to the muscles and bones. The folds probably
formed in the joint areas between bones, just as skin folds at joints in
modern animals.
As we said earlier, the scale patterns on our embryos were similar to
the clusters of bony plates called scutes that had been discovered
around the skeleton of
Saltasaurus.
The armor of
Saltasaurus
is
formed by hundreds of small, closely packed, bony scutes—roughly
the size of our fingernails—which are occasionally separated by four-
inch-long, oval scutes adorned with a central ridge. This combination
of large and small scutes occasionally forms roselike patterns. Both
kinds of scutes are thought to have "floated" in the dinosaur's hide,
although on certain areas of the body the scutes are so tightly packed
that they would have formed a pavement of armor. Since the dis-
covery of
Saltasaurus,
diverse scutes of other titanosaurs have been
found in other parts of South America, Madagascar, and Europe.
These discoveries have prompted the reinterpretation of scutes from
earlier discoveries of titanosaurids, which had led to the belief that
other kinds of armored dinosaurs such as ankylosaurids lived in South
America.
Cross sections of the embryonic skin patches did not reveal bone.
Nonetheless, the striking resemblance between the patterns on our
embryos' skin and on
Saltasaurus
made us think that the bony armor
of the adult titanosaur could have been formed as a one-to-one repli-
cation of the embryonic pattern of scales. This one-to-one replication
is typical of modern armored reptiles, such as crocodiles and Gila
monsters. Once again, our discovery suggested that the processes that
control the development of modern animals were at work during
the growth cycle of ancient dinosaurs. Although we believe that the
scales of our embryos might constitute the model over which armor
formed in adults, the smooth surface of our embryos' scales did not
show any of the central crests seen in the larger scutes of
Saltasaurus
and other titanosaurs. It may be that these crests represent over-
growths developed during the formation of the bony scutes, or that
perhaps crests were not present on the scutes of all sauropods.
All in all, our forensic studies revealed that the embryonic bones,
teeth, and skin from Auca Mahuevo belonged to a large group of
