Geoscience Reference
In-Depth Information
That was exciting just by itself. So you can imagine how it felt to receive ad-
ditional news a week later from Dave that said this:
There's a
second
one [juvenile].
This called for another happy dance. It is hard enough to find one dinosaur,
let alone three of the same species, and possibly from the same family, all together.
Although this specimen was also incomplete, enough of its bones were there to dis-
tinguish it from the other, and their matching bones were the same size. These di-
nosaurs could have been brother and sister to one another, and might have been en-
tombed together with one of their parents in a burrow. This revelation strengthened
our denning hypothesis, albeit while also conjuring sad thoughts of parental loss.
More pertinent information came in as Dave studied the bones, looking for
anatomical clues that might tell him whether the adult dinosaur was capable of bur-
rowing. Once he finished his study, three relevant traits stood out. First, one of the
bones integral to its shoulder—the scapulocoracoid—had attachment sites for large
muscles. This meant it had the right musculature for using its forelimbs in bur-
rowing, similar to that of modern burrowing mammals like armadillos. Second, the
bone on the front of its snout—the premaxilla—was fused, an unusual feature in a
dinosaur. This reinforced its nose, making it easier to use as a small spade to aug-
ment the dinosaur's busily digging hands. Third, when compared to its closest re-
latives (other small ornithopods), its hip had an extra vertebra. For example,
Oro-
dromeus
had six vertebrae in its hip, whereas this newcomer had seven. Dave sur-
mised that this additional vertebra strengthened its hip, which the dinosaur used as
a brace while digging. As anyone might notice while watching his or her dog dig
under a neighbor's fence, dogs anchor themselves into digging position with their
rear legs while scratching enthusiastically with their front feet; only later are the
rear feet used for excavating. It was now easy to imagine that this dinosaur, with
three adaptations for a burrowing lifestyle, would have behaved similarly.
