Geoscience Reference
In-Depth Information
the embryos were titanosaurids, diplodocids, or another of their close
relatives.
Another of our eggs contained several leg bones that fit up against
one another. Although they did not prove helpful in precisely identi-
fying our embryos, they established the approximate size of the
embryo inside the egg. The thighbone, or femur, was about four
inches long, twice as long as the skull of the other embryo, indicating
that this embryo would have been ten to twelve inches long when it
hatched. In adult sauropods, such as
Diplodocus,
the femur is four or
five times longer than the skull. Although we cannot be sure whether
the embryos were closer relatives of titanosaurs or diplodocids, all of
these dinosaurs were enormous, and it is clear that our embryos
would have grown into some of the largest animals ever to walk on
earth. But what about the suspected fossils of embryonic dinosaur
skin? Did those show similarities to previously known fossils of adult
sauropod skin?
Fossils of adult sauropod skin have been known since the mid-
1800s. The pattern of skin ornamentation in our embryos looked sim-
ilar to that of other sauropod dinosaurs, such as
Diplodocus.
The skin
in sauropods is formed by polygonal tubercles of varying size that do
not overlap with one another. Recent discoveries have shown that
these late Jurassic
Diplodocus
had a row of narrow spines running
along their tails, like those of crocodiles, and some scientists argue
that this series of spines would also have extended along the back and
neck. None of the patches of fossilized skin that our crew found
indicate the presence of spines on our embryos, but we believe that
the triple row of larger scales found on our babies did extend along
the entire tail, back, and neck. The difference between this pattern of
embryonic scales and the pattern of spines in adult
Diplodocus
and its
kin might suggest that the spines were used as a visual signal that
allowed individual
Diplodocus
to recognize one another, perhaps at
the time of selecting a mate.
The skin of our embryos exhibited a diverse array of scale patterns.
In one, as mentioned above, a triple row of larger scales crossed a field
of smaller scales. In others, we found scales arranged in rosette pat-
terns, in which a circle of eight smaller scales surrounded a large cen-
tral scale. Still other specimens revealed several triangular scales that
converged toward a central point, like the petals of a flower. But
