Geoscience Reference
In-Depth Information
dinosaurs called neosauropods, which includes famous dinosaurs
such as
Diplodocus, Camarasaurus, Brachiosaurus, Titanosaurus,
and
Argentinosaurus.
In a sense, we had discovered the smallest fossils of
the largest dinosaurs. Our trip had succeeded beyond our wildest
dreams, and our crew's discoveries represented several firsts for pale-
ontologists. Most important, our discovery represented the first indis-
putable embryos of sauropod dinosaurs. Even though thousands of
eggs attributed to sauropods had previously been found in France,
Spain, India, Argentina, China, and other parts of the world, no
definitive
embryos of sauropod dinosaurs had ever been found until
our team's discovery. A few small fossils from young sauropods had
previously been discovered, and some paleontologists had argued
that they represented embryos; however, they were either too big to
really be embryos, or they were not found inside an egg—the defini-
tive proof that a specimen had not yet hatched. At last, we could be
certain that at least some sauropods laid eggs and that the large eggs
previously identified as belonging to sauropods actually were sauropod
eggs. Our embryos were also the first dinosaur embryos ever discovered
in the Southern Hemisphere. Most dinosaur nesting grounds are
concentrated in the northern continents, so the discovery of a large,
new nesting ground in South America contributed important new
insights to our knowledge about the reproductive biology of dinosaurs
from the southern continents. Finally, the eggs also contained the first
embryonic dinosaur skin ever discovered. So, for the first time, we
could sense what it would have felt like to touch an unhatched baby
dinosaur that would have grown up to become one of the largest ani-
mals ever to walk the earth. The discovery of embryonic sauropod skin
also led to other important inferences concerning the biology of
dinosaurs. As noted earlier, some scientists have argued that
Tyran-
nosaurus
was covered with feathers as a juvenile and that it lost those
feathers as it grew into adulthood. This inference is based on the close
evolutionary relationship between birds and
Tyrannosaurus
on the
family tree of theropods. Sauropods are not theropods but are included
with theropods in the larger group called saurischians. That adult
sauropods and theropods more primitive than
Tyrannosaurus
and its
coelurosaur relatives lacked feathers when adults was already known
from several specimens with preserved portions of skin. Our discovery
made clear that not all saurischians were covered with feathers during
