Corythosaurus: Beast of the Week

This week we will take a look at a well known duckbill dinosaur.  Enter Corythosaurus!  

Corythosaurus was a plant eater that belonged to the lambiosaurine group within the family, Hadrosauridae. (duckbills)  Lambiosaurine hadrosaurs typically had hollow crests on their heads and narrower beaks compared to other kinds hadrosaurs.  It was closely related to other lambiosaurine hadrosaurs such as Parasaurolophus, Hypacrosaurus, Lambeosaurus, and Velafrons.  It lived in what is now Alberta, Canada, during the Late Cretaceous period, between 77 and 76 million years ago.  Corythosaurus could have measured up to 30 feet (about 9m) long from beak to tail and its genus name translates to "helmet lizard/reptile" because of its tall disc-shaped crest, which in profile resembles a helmet.  

Corythosaurus cassuarius life reconstruction in watercolors by Christopher DiPiazza.

Corythosaurus actually includes two distinct species.  Corythosaurus cassuarius was had a larger crest and was found in rocks that about 1 million years older, and Corythosaurus intermedius, which had a slightly smaller crest and was found in slightly younger rocks.

There are two species of Corythosaurus currently known.

The crest of Corythosaurus, despite the name, wasn't really a helmet.  (Although another group of dinosaurs, the pachycephalosaurs, did have skulls that were more literally helmet-like.)  Its crest was semi-circular, and hollow on the inside, housing a network of tubes that likely connected the animal's nostrils to its windpipe.  Originally scientists thought this was an adaptation for a semi-aquatic lifestyle, but they were most likely for amplifying the sounds that Corythosaurus made.  Corythosaurus could inhale through its nostrils, where the air would pass through the series of tubes before being released through the mouth, thus producing a louder sound, much like the inner workings of trumpets or other brass wind instruments.  Sound was probably a very important method of communication for Corythosaurus and its relatives.  

Juvenile Corythosaurus skull on display at the Royal Ontario Museum in Canada.  Note the proportionally much smaller crest.

Thanks to a beautifully preserved specimen of Corythosaurus, paleontologists were able to discover highly developed inner ear bone, further supporting this idea.  The Corythosaurus genus used to consist of several species with similar crests of varying sizes.  It was later realized, however, that these specimens were more likely different ages and sexes of the same species since they were all found in the same area together and the largest specimens had the largest crests.  Furthermore, if adult male and female Corythosaurus also had different looking crests, they would have had different sounding calls.  We can see this today with their modern relatives, the birds and crocodilians, as well as other kinds of animals like frogs and insects.  It is possible lambiosaurid dinosaurs practiced similar behaviors, using sound to announce their age and sex over longer distances than they could with just looks.  Since more than one different kinds of these duckbills would have lived in the same place during the same time (Corythosaurus and Parasaurolophus, for instance.) it would make sense that each would have different crests to make different sounds and thus, preventing any identity confusion just like all the kinds of birds and frogs within the same community each have their unique calls today. 

Corythosaurus skeleton, which includes patches of skin and other soft tissue, on display at the American Museum of Natural History in New York.

Corythosaurus is amongst the most well-studied of the non-avian dinosaurs because one specimen that was unearthed in the early 1900s not only included nearly every single bone in the skeleton, but it also preserved skin, organs, and even the animal's last meal!  Thanks to this individual, now on display at the American Museum of Natural History in New York, we know that Corythosaurus would have had pebbly, mosaic-like scales that varied in size to form patterns on its skin.  It also had padding under its feet and hands, which scientists in the early 1900s originally thought would have been webbing for swimming, further supporting the now debunked aquatic hypothesis.  In the stomach cavity were the remains of conifer needles, sticks, and seeds.  These plant foods would have been plucked with Corythosaurus' narrow, flat beak and chewed up with its hundreds of tiny teeth lining the back of its jaws. 

When alive, Corythosaurus would have coexisted with many other well-known dinosaurs, like close relative, Parasaurolophus, the horned ceratopsian, Chasmosaurus and, the tyrannosaur, Gorgosaurus.

That is all for this week!  As always feel free to comment below!

References

Barden, Holly. "Sexual dimorphism in dinosaurs: a review of the evidence and approaches" (PDF). APS 402 Dissertation. University of Sheffield. Retrieved 13 August 2013.

Bell, P. R. (2012). "Standardized Terminology and Potential Taxonomic Utility for Hadrosaurid Skin Impressions: A Case Study for Saurolophus from Canada and Mongolia". In Farke, Andrew A. PLoS ONE 7 (2): e31295.

Dodson, P. (1975). "Taxonomic implications of relative growth in lambeosaurine dinosaurs". Systematic Zoology 24 (1): 37–54.