Saichania
Name: Saichania
(Beautiful one).
Phonetic: Sie-chan-ee-ah.
Named By: Teresa Maryańska - 1977.
Classification: Chordata, Reptilia, Dinosauria,
Thyreophoroidea, Ornithischia, Ankylosauridae, Ankylosaurinae.
Species: S. chulsanensis
(type).
Diet: Herbivore.
Size: Up to 6.6 meters long.
Known locations: Mongolia, Nemegt Basin -
Barun Goyot Formation.
Time period: Campanian of the Cretaceous.
Fossil representation: Skulls and post cranial
remains.
At
over six meters long Saichania is one of the larger
known
ankylosaurids, although in terms of size it would probably be
eclipsed by the larger Tarchia
which is also known from the same
formation, and was actually described at the same time as Saichania.
The actual meaning of the name Saichania
(beautiful one) is based
upon the condition of the holotype fossils that were recovered in a
high state of preservation.
One
feature of interest about Saichania is the hard
palate in the mouth
(if you touch the tip of your tongue to the roof your mouth you feel
that it is hard, this is your palate). Hard palates are virtually
unknown in dinosaurs as a group, but they have been documented in
other ankylosaurid dinosaurs like Euoplocephalus,
which suggest that
as a group the ankylosaurids dinosaurs were quite well developed.
This means that Saichania would be able to breathe
while its mouth was
full of plants; as such Saichania could afford to
spend more time
processing food with up and down jaw movements to allow for much more
efficient digestion. Also Mongolia during the Late Cretaceous was
covered by vast areas of arid landscape, the plants of which would
have been tougher and requiring more digestion than the soft vegetation
of wetlands.
While
the hard palate would have helped in the above respect, it would have
also made it easier for Saichania to breathe
through the network of air
passages that were present in the snout. Earlier nodosaurids
(thought to be the group the ankylosaurids are descended from) like
Nodosaurus
had simple passages that ran straight from the nostrils to
the windpipe, so it seems strange that the ankylosaurids should
develop such a system, at least until you consider the
environmental effects of where they lived.
Asian
ankylosaurids would have lived in environments that were almost always
arid, and as such dry. Breathing in dry air can dry out the lungs,
causing an increased amount of moisture to be lost through
respiration, and prolonged exposure can even trigger respiratory
ailments as well. But having breathed in air that passed through a
network of passages first, the air becomes moistened in the snout,
significantly reducing the amount of moisture lost. Additionally
breathing through the nose itself also greatly reduces the amount of
water lost as to what would happen if breathing was through the mouth,
and is why survival experts will tell you to breathe through your nose
and not your mouth if you are ever stuck in the desert.
Altogether
the features of Saichania have helped reveal how
well adapted to dry
environments that the ankylosaurids were. Also while North American
ankylosaurids lived in a greater variety of environments, they still
possessed these adaptations, perhaps to better cope with seasonal wet
and dry periods. Evidence for this can actually be found associated
with the nodosaurid Edmontonia,
as nearby petrified tree trunks
have growth rings that correspond with extended wet and dry periods.
The
top of the skull of Saichania is covered in bulbous
growths, a
feature it shares not only with Tarchia but the
North American
Nodocephalosaurus
as well. This hints at a common
ancestry between
these three ankylosaurid genera.
Further reading
- Ankylosauridae (Dinosauria) from Mongolia - Palaeontologia Polonica
37:85-151 - Teresa Maryańska - 1977.
- A new method to calculate allometric length-mass relationships of
dinosaurs. - Journal of Vertebrate Paleontology, 21(1): 51–60 - F.
Seebacher - 2001.
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