Dilong
Name: Dilong
(Emperor
dragon).
Phonetic: Die-long.
Named By: Xu Xing et al - 2004.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Tyrannosauroidea.
Species: D. paradoxus (type).
Type: Carnivore.
Size: Up to 2 meters long.
Known locations: China, Liaoning Province,
Yixian Formation.
Time period: Barremian of the Cretaceous.
Fossil representation: Several remains, together
revealing much of the Skull and post cranial skeleton. Impressions of
protofeathers have also been found with fossils.
One
thing that made Dilong stand out from other
dinosaurs upon its
discovery was the impressions of protofeathers. These protofeathers
were not capable of enabling flight, but were very good at
insulating, keeping heat in the body. A higher base temperature for
a cold blooded creature means a faster metabolism and more active
life. However, the protofeathers would also allow a warm blooded
creature to maintain body temperature for less effort.
Either
way, the presence of protofeathers in Dilong
indicate that it was an
active hunter that relied upon being swift enough to catch prey,
probably other and smaller dinosaurs as indicated by its own size.
It is also likely that Dilong went for other
smaller reptiles such as
lizards, as a high metabolism requires a higher calorie intake to
maintain. Small dinosaurs in general might not have had to eat a
lot, but they may have had to eat often.
The
feathers in Dilong also help reinforce the theory
of gigantothermy in
large dinosaurs. Many of the later and smaller theropods display
feathers, Troodon
and Velociraptor
being good examples. This is
because they have small body mass to surface area ratios, meaning
that they can lose internal heat quite easily, even if they do not
want to. The protofeathers seen in Dilong and
others probably
evolving for insulation. Skin
impressions for larger theropods like Tyrannosaurus,
show that they
just had bare skin, and this is because the larger dinosaurs had
larger body mass to body surface ratios. This means that the internal
body parts were already insulated by other body parts, which got
insulated again by other tissue layers before heat could reach the
skin.
Adding feathers on top of that would likely cause the creature to
overheat, possibly to the point of illness and even death. There are
exceptions to this however with the discovery of Yutyrannus,
tyrannosaur
known to grow up to nine meters long and yet still have
feathers, possibly as a result of living in a colder climate.
When
it was described, Dilong was described as a basal
member of the
tyrannosaurids, and today that classification holds true for most.
However because of its features some people consider Dilong
to
actually be a member of the Coelurosauria.
Further reading
- Basal tyrannosauroids from China and evidence for protofeathers in
tyrannosauroids - Nature 431 (7009): 680–684. - X. Xu, M. A. Norell, X.
Kuang, X. Wang, Q. Zhao & C. Jia - 2004.
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