Geoscience Reference
In-Depth Information
Superficially,
Velociraptor
and other well-known maniraptors may
appear very different from living birds. While the fearsome star of
Jurassic Park
possessed large claws and sharp teeth, birds lack both
these features. Yet, a closer examination of the skeletons in birds and
Velociraptor
reveals numerous similarities, and these become even
clearer when one compares the skeleton of
Velociraptor
with those of
ancient Mesozoic birds.
Birds not only share the unique structure of the hips and wrists
found in other maniraptors, but also the long arms of coelurosaurs, the
three-fingered hands of tetanurans, the three-toed feet of theropods,
and the perforated hip socket of dinosaurs. In addition, they have
feathers, like their most immediate forerunners among the manirap-
tors and coelurosaurs. In the last few years, spectacular discoveries
from the northeastern corner of China have shown that the body of
maniraptors was also covered with feathers. A close cousin of
Veloci-
raptor,
the Chinese maniraptor called
Sinornithosaurus
had two-to-
three-inch-long downy feathers covering its skin. The fact that
feathers, long thought to be a characteristic unique to birds, have been
found on fossil skeletons of other maniraptoran dinosaurs has dealt the
final blow to paleontologists who doubted that birds evolved from
dinosaurs. Today, we can declare that birds are dinosaurs with the same
degree of confidence that we can say that humans are primates.
Birds experienced a long and complex evolutionary history, most of
which was played out in the Mesozoic era. The earliest known bird is
Archaeopteryx,
which lived about 150 million years ago in the late
Jurassic period. Exquisite fossils of this crow-sized bird were first
found in the limestone quarries of southern Germany in the mid-
1800s. The skeleton of
Archaeopteryx
still had a very dinosaurian
appearance, with a long tail, sharp teeth, and powerful claws on its
wings, although its plumage was fully modern. Within 20 million
years after
Archaeopteryx
lived, birds had already evolved with a more
typical, stumpy tail and wings that gave them a more modern appear-
ance, though birds would retain their teeth throughout the Mesozoic.
Another early branch on the family tree of birds contains all
Enantiornithes, who were sophisticated fliers, even though the first
known members of the group lived as early as 125 million years ago.
It is rather amazing to realize that even that far back in time, birds
were able to perform the same aerodynamic feats that they delight us
