Arrhinoceratops
Name:
Arrhinoceratops
(No nose-horn face).
Phonetic: Ar-rye-no-sore-us.
Named By: William Arthur Parks - 1925.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Ceratopsia, Ceratopsidae, Chasmosaurinae.
Species: A. brachyops
(type).
Diet: Herbivore.
Size: Uncertain due to lack of post cranial remains.
Known locations: Canada, Alberta - Horseshoe
Canyon Formation.
Time period: Campanian/Maastrichtian of the
Cretaceous.
Fossil representation: Partial skull.
An
often included genus in dinosaur books, Arrhinoceratops
is another
example of a popular dinosaur known by very little fossil material.
In this case Arrhinoceratops has been based upon
the description of
only a single partially preserved skull. Arrhinoceratops
was named
because William Parks thought that it lacked a nasal horn, and too an
extent this is true. In some ceratopsians
such as centrosaurines,
that horn is established by a horn core that grows from the upper
snout of the skull. As a chasmosaurine ceratopsid, Arrhinoceratops
would not have had a horn core but the nasal bones would have still
likely grown into a point like projection that would have resembled a
small horn.
There
have been many attempts to gauge the size of Arrhinoceratops,
but
without at least some elements of the post cranial skeleton, only a
best guess by means of comparing the holotype skull with the skulls of
other genera. Without a more exact figure, it is easier to just say
that Arrhinoceratops was more of a medium sized
ceratopsian, on a
scale where two to three meters is small, and anything over five to
six meters is large.
The
neck frill of Arrhinoceratops is noted as having
many deep grooves
running along and into the bone. In life these grooves would have
been filled by blood vessels that would have supplied the soft tissue
that was supported by the bony interior with oxygenated blood. In the
past this has been argued to be a thermoregulation device for
warming/cooling the blood, but just as if not more likely is that
blood could be forced into the frill to produce a more intense colour
display on the frill. In dominance contests the individual that
could maintain the extra flow for longer would be seen as the more
healthy and therefore most worthy of mating.
Arrhinoceratops
was not the only ceratopsian dinosaur present in its ecosystem with
fossils of Pachyrhinosaurus,
Anchiceratops
and Eotriceratops
all
being found in the same fossil formation. Other kinds of dinosaurs
that Arrhinoceratops may have come into contact
with include hadrosaurs
like Hypacrosaurus,
Edmontosaurus
and Saurolophus,
while predatory
threats could have come from large tyrannosaurs
such as Albertosaurus.
Further reading
- Arrhinoceratops brachyops, a new genus and
species of Ceratopsia
from the Edmonton Formation of Alberta, William Arthur Parks -
1925.
- A revision of the Ceratopsia or horned dinosaurs, R. S. Lull
- 1933.
- Reptilian fauna of the North Horn Formation of central Utah, C.
W. Gilmore - 1946.
- Tyrannosaurus and Torosaurus,
Maestrichtian dinosaurs from
Trans-Pecos, Texas, D. A. Lawson - 1976.
- The structure and relationships of the horned dinosaur
Arrhinoceratops Parks (Ornithischia:
Ceratopsidae), H. Tyson
- 1981.
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