Gryposaurus
Name:
Gryposaurus
(hook nosed lizard).
Phonetic: Grip-o-sore-us.
Named By: Lawrence Lambe - 1914.
Synonyms: Hadrosauravus, Hadrosaurus
notabilis, Kritosaurus incurivmanus, Kritosaurus incurvimanus,
Kritosaurus notabilis.
Classification: Chordata, Reptilia, Dinosauira,
Ornithischia, Ornithopoda, Hadrosauridae, Saurolophinae.
Species: G. notabilis
(type), G. latidens, G. monumentensis.
Diet: Herbivore.
Size: Up to around 8 and 9 meters long.
Known locations: Canada - Alberta- Dinosaur
Park Formation, USA - Montana - Two Medicine Formation,
Utah - Kaiparowits Formation.
Time period: Late. Santonian to Campanian of the
Cretaceous.
Fossil representation: Multiple skulls and sets of
post cranial remains.
Gryposaurus
has a long standing and convoluted association with the genus
Kritosaurus
to the point that in the 1920‘s Gryposaurus was
actually regarded as a synonym to Kritosaurus.
Later study has since
interpreted Gryposaurus as a distinct genus, but
this thinking has
had the effect of emptying most of the known material for Kritosaurus
into Gryposaurus. Also the idea of Gryposaurus
and Kritosaurus being
the same is still questioned by many palaeontologists on the grounds
that Kritosaurus is known from only partial remains
that seem to differ
from Gryposaurus in terms of geographical location.
Past
speculation around the 1970s to 1980 also suggests that
Gryposaurus and Kritosaurus
might be synonyms of Hadrosaurus,
though
by the 1990s they were once again regarded as being different
because of differences in the ilium (one of the bones of the pelvis)
and the upper arms. Further fossils and research might one day call
for Gryposaurus to be re-synonymised with Kritosaurus,
but for the
time being at least Gryposaurus and the species
attributed to it are
treated as valid.
The
technical classification for Gryposaurus is that it
is a saurolophine
hadrosaurid.
Though older texts still describe Gryposaurus as a
hadrosaurine, this is no longer in common use since Hadrosaurus
was
found to be different from other genera previously labelled as
hadrosaurines. Because of this Hadrosaurus was
given its own place
beneath the Hadrosauridae, but the term Hadrosaurinae had to be
disbanded because it no longer contained the genus Hadrosaurus.
From
here the next oldest genus of the group, Saurolophus,
was
established as the type genus of the group now known as the
Saurolophinae, and hence why Gryposaurus is
currently classed as a
saurolophine.
Gryposaurus
is of course also known as a duck billed dinosaur because of the
specially adapted mouth that was suited for snipping vegetation. Once
a mouthful was obtained, the rear tooth batteries went to work
grinding the teeth in a fashion that was similar to chewing yet
different to how we and animals chew today. Instead of a flexible
lower jaw, the upper jaws are believed by many palaeontologists to
have come away from the skull so that the upper and lower teeth could
slide over each other and grind the plant matter.
There
is still a lot of contention as to exactly which kinds of plants
hadrosaurids ate, with popular ideas suggesting soft aquatic plants
while fossil evidence actually points to tougher terrestrial plants
that do not normally grow in wetland ecosystems. An obvious advantage
that Gryposaurus and other hadrosaurid dinosaurs
had however was the
ability to shift between quadrupedal and bipedal postures, and
ability that allowed them to either feed low down to the ground, or
as much as a few meters above it.
Many
fossil locations of Gryposaurus coincide with areas
that would have
been near the coast of the Western Interior Seaway, a shallow
Cretaceous sea that submerged most of North America from the Gulf of
Mexico all the way up to the Arctic Ocean. These areas would have
been areas of wetlands, swamps, marshes and river deltas, though
these do not necessarily have to be the only ecosystems that
Gryposaurus was active in, just the one supported
by fossil evidence.
As
a saurolophine hadrosaurid, Gryposaurus lacked an
elaborate hollow
crest that is the signature feature of the lambeosaurine hadrosaurids.
Instead the nasal arch of the skull bowed upwards to produce and arch
over an enlarged nasal opening, something that has been interpreted
as a possible housing for large amounts of soft tissue. If this
interpretation is correct, then Gryposaurus might
have had a display
feature made up from soft tissue rather than the hollow bony crests of
the lambeosaurines. Additionally the nasal arch in some skulls has a
rough texture which might indicate the presence of a keratinous growth
and possible extension of the feature by further keratin or even
cartilage. Although not directly related, many pterosaurs
are also
known to have had skull crests constructed in a similar fashion where a
keratinous crest attached to a skull via and enlarged bony growth to
help anchor it in place.
Further reading
- On Gryposaurus notabilis, a new genus and
species of trachodont
dinosaur from the Belly River Formation of Alberta, with a
description of the skull of Chasmosaurus belli,
Lawrence M. Lambe
- 1914.
- Upper Cretaceous dinosaurs from the Bearpaw Shale (marine) of
south-central Montana with a checklist of Upper Cretaceous dinosaur
remains from marine sediments in North America, J. R. Horner,
1979.
- A new species of Gryposaurus (Dinosauria:
Hadrosauridae) from
the late Campanian Kaiparowits Formation, southern Utah, USA,
Terry A. Gates & Scott D. Sampson - 2007.
- The braincase and skull roof of Gryposaurus notabilis
(Dinosauria,
Hadrosauridae), with a taxonomic revision of the genus. - Journal of
Vertebrate Paleontology. 30 (3): 838–854. - Alberto Prieto–Marquez -
2010.
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