Geoscience Reference
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unfortunately, it is not possible to say exactly where these scale
arrangements were located on the body because the patches of fos-
silized skin did not overlap identifiable bones in the skeleton.
Several titanosaur specimens, all apparently close relatives of the
late Cretaceous titanosaur from northwestern Argentina called
Saltasaurus,
were known from the same late Cretaceous rocks that
we were exploring near Auca Mahuida.
Saltasaurus
is well known
because it is covered with a fully armored skin, presumably for pro-
tection from the large meat-eating dinosaurs that lived at the time.
Although armor is common in other groups of dinosaurs, including
the stegosaurs and the ankylosaurs, it is not usually preserved with
the skeletons of sauropods. In fact, it was not until the 1970s, when
Saltasaurus
was first found, that paleontologists realized that some
sauropods possessed a covering of bony armor. We noticed that the
pattern of armor plating in the skin of
Saltasaurus
was remarkably
similar to the pattern of bumps on the skin of the embryos from
Auca Mahuevo, which made us wonder whether we would find bony
tissue within the skin of our embryos.
To study the skin of our embryos more closely, we wanted to take
photographs using a stereo electron microscope and cut cross sections
through the skin to study under other microscopes. Our SEM at the
American Museum of Natural History required the specimens to be
coated with a thin layer of gold or platinum paint before images
could be taken, but we did not want to coat our real specimens.
(Ironically, they are much more valuable to us without a gold or plat-
inum coating than with one.) So we produced a rubber mold of our
most complete patch of skin and made a resin cast of the skin from it.
This perfectly replicated patch of embryonic dinosaur skin was coated
with a thin layer of gold and then photographed. Luckily, we also
obtained images of our embryonic skin outside the American Museum
of Natural History using a more sophisticated electron microscope,
which did not require the specimens to be coated.
Even at high levels of magnification, our embryonic dinosaur skin
looks quite similar to the skin of other reptiles, like a blanket of
round, scalelike knobs of similar size. In contrast to the scales on most
modern lizards and snakes, the scales of our embryos did not overlap
one another, just as in the case of fossilized skin from adult dinosaurs.
In this respect, the skin of dinosaurs, including that of our embryos,
