Corythosaurus
Name:
Corythosaurus
(Helmet lizard).
Phonetic: Cor-ith-o-sore-us.
Named By: Barnum brown - 1914.
Synonyms: Corythosaurus bicristatus,
C. brevicristatus, C. excavatus, C. frontalis,
Stephanosaurus
intermedius.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Ornithopoda, Hadrosauridae, Lambeosaurini.
Species: C. casuarius
(type), C. intermedius.
Diet: Herbivore.
Size: Average of 9 meters long. Some individuals
slightly larger.
Known locations: Canada, Alberta. USA, Montana.
Time period: Campanian of the Cretaceous.
Fossil representation: Multiple specimens, some of
almost complete individuals. Some soft tissue remains/impressions are
also known.
Corythosaurus
acquired its name from the shape of the head crest on the back of its
skull which resembles a Corinthian helmet from ancient Greece.
Because this head crest was hollow, Corythosaurus
is today classed
as a lambeosaurine hadrosaurid.
The lambeosaurine hadrosaurs which
also include other famous genera such as Parasaurolophus
as well as the
type genus Lambeosaurus
all have hollow crests, and like with these
there is a recurring theory that this hollow crest may have been a
resonance chamber for amplifying calls. Critics have stated that if
this were true then lambeosaurine crests should be all the same, but
this misses the fact that different shapes could have produced
different types of call which would have enabled different genera of
lambeosaurines to identify one another by sound alone. Also, one
Corythosaurus specimen is noted for having a large
eardrum but slender
stares (reptilian ear bone) which indicates that hearing was well
developed and probably one of the most important senses used.
Additionally
this may have allowed a single Corythosaurus to
sound out a warning
call to other nearby individuals at the sight of a predator. This
would infer behaviour where Corythosaurus may have
moved around in
groups or even herds where the eyes of many individuals were looking
out for danger, something that would significantly increase the
survival chances of Corythosaurus over what they
would have been if
they were solitary animals.
A
more mundane explanation for the hollow head crest is that it was
simply a way to reduce the crests weight. This would imply that
Corythosaurus used the crest as a visual display,
perhaps not only to
attract mates but to identify other lambeosaurine hadrosaurids of its
own genus from other similar dinosaurs, something that has also been
suggested for variations in the horns and frills of ceratopsian
dinosaurs that also lived in North America at the same time as
Corythosaurus. Out of all the other currently
known lambeosaurine
dinosaurs Olorotitan
is considered to be one of the closest relatives
of Corythosaurus.
The
diet and ecosystem of dinosaurs like Corythosaurus
is currently a
matter of dispute. The classical view of Corythosaurus
for example
has been of a semi bipedal dinosaur that waded into the edges of swamps
and lake to feed. This scenario stems back to the first descriptions
of hadrosaur dinosaurs in the latter decades of the nineteenth century
when the skulls, jaws and teeth were interpreted as being too weak
to process anything but soft aquatic plants. This thinking was
however flawed because many of the skulls and jaws examined were
incomplete. Study in the latter half of the twentieth century and
on-going into twenty-first century not only suggests that Corythosaurus
and other hadrosaurs were capable of processing regular terrestrial
vegetation like other herbivores, but fossil evidence in the form of
stomach contents reveals that hadrosaurs would at least on occasion eat
terrestrial plants from dryer inland habitats.
The
modern interpretation of Corythosaurus is usually
of a quadrupedal
herbivore that could on occasion walk about on just the rear legs when
it had to, feeding upon low growing vegetation inland, although
possibly rearing up to browse higher growing vegetation. This
however could have put them in competition with ceratopsians
as well as
possibly ankylosaurs, two groups of dinosaurs that were only capable
of feeding upon low vegetation. Feeding on aquatic plants would still
have been a viable option for Corythosaurus,
particularly in times
when other plants were not as readily available.
One
observation previously used to reinforce the theory that Corythosaurus
fed upon aquatic plants while in the water was the discovery of what
looked like webbing between the toe bones. While initially heralded
as proof of the aquatic theory, later study revealed that this
‘webbing’ was merely the remnants of the skin left behind after the
flesh had decomposed. In life the toes would have been fleshy just
like any other land animal. A simpler analogy is to think of a
balloon that has been found a few days after a party but is now
deflated. In this state it is a flat piece of wrinkled rubber, yet
a few days before it was large, round and filled with gas. This is
the true form of the function of the balloon, but the deflated
version that is found later could give a false representation to what
it actually is to someone who was not around to see it at the party.
Regardless
of which kinds of plants Corythosaurus fed upon,
the hard beak that
ran across the front of the mouth would have been used to grip and
separate small mouthfuls from the plant it was feeding upon. This
mouthful would then be processed by grinding batteries of small teeth
at the back of the mouth before swallowing. To help with the food
processing, Corythosaurus is often envisioned as
having cheeks that
would help prevent the plant matter from falling out of the sides of
the mouth while it was being processed in this way.
Dinosaurs
are known to have had scleral rings like birds do, but they are not
always preserved. Fortunately the scleral rings of Corythosaurus
have
been found and studied, revealing them to be those of a cathemeral
creature. What this means is that Corythosaurus
would be active for
short periods during the day and night. Although this might sound
unusual cathemeral lifestyles have been suggested for many dinosaurs.
This might suggest that when Corythosaurus
foraged, food was only
eaten in moderation to be digested quickly in smaller amounts. Being
cathemeral might have also given Corythosaurus the
flexibility to live
alongside other herbivores in the ecosystem that were either diurnal
(active during the daytime) as well as those that were nocturnal
(active during the night time).
Likely
predators of Corythosaurus could have included tyrannosaurs
such as
Albertosaurus
or perhaps even Tyrannosaurus
itself. Other dinosaurs
that might have been a threat were the smaller troodontids such as the
type genus Troodon
which may have been a particular threat to much
smaller Corythosaurus juveniles.
Corythosaurus has an association with the often infamous merchant vessel the SS Mount Temple. When the passenger liner RMS Titanic sank in 1912, the SS Mount Temple was one of the ships that responded to the distress call, yet just before she arrived the ships master Capt. Moore ordered a full stop on the claim that the ice was too thick to approach, a decision that has been questioned and remains controversial to this day. In 1916 during the First World War the SS Mount Temple was carrying mixed cargo of mostly war supplies but also fossil specimens that had been collected by renowned palaeontologist Charles H. Sternberg, which also included specimens of Corythosaurus. On December 6th, the SS Mount Temple was intercepted in the North Atlantic by the German surface raider SMS Möwe, an auxiliary cruiser masquerading as a merchant vessel. After a short battle the Mount Temple, which wss armed only with a single gun, was easily overwhelmed by the superior firepower of the German cruiser and surrendered. After the passengers and surviving crew were taken aboard the SMS Möwe, the German sailors scuttled (deliberately sank) the SS Mount Temple with explosives placed below the waterline. Everything aboard including the Corythosaurus remains ended up on the bottom of the Atlantic.
Further reading
- Corythosaurus casuarius, a new crested
dinosaur from the Belly
River Cretaceous, with provisional classification of the family
Trachodontidae, Barnum Brown - 1914.
- Corythosaurus casuarius: Skeleton, Musculature
and Epidermis. -
American Museum of Natural History Bulletin. 38. - Barnum Brown - 1916.
- New species of crested trachodont dinosaur. - Bulletin of the
Geological Society of America 34:130. - W. A. Parks - 1923.
- The braincase and skull of Gryposaurus notabilis
(Dinosauria,
Hadrosauridae), with a taxonomic revision of the genus. - Journal of
Vertebrate Paleontology 30(3). - A. Prieto-Marquez - 2010.
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