Corythosaurus

Corythosaurus is a genus of duck-billed hadrosaurid dinosaur that lived during the Late Cretaceous, roughly 77 to 75.7 million years ago, in what is now western North America. Its name comes from the Greek word for "helmet," and it was named and described by Barnum Brown in 1914. Today, Corythosaurus is classified as a lambeosaurine, placing it in the same group as Lambeosaurus, Nipponosaurus, Velafrons, Hypacrosaurus, and Olorotitan. The animal had an estimated length and a tall skull that included its distinctive crest.

Many complete specimens of Corythosaurus have been found, including the nearly complete holotype that Brown collected in 1911. That holotype skeleton is missing only the last section of its tail and parts of its front legs, but it was preserved with impressions of polygonal scales. Numerous skulls have also been recovered, each with a tall crest that resembles the crest of a cassowary or a Corinthian helmet. The crest likely functioned in vocalization: when the animal exhaled, sound waves traveled through chambers inside the crest and were amplified, similar to how a trombone works. One specimen even preserved its last meal in its chest cavity, which contained conifer needles, seeds, twigs, and fruits, suggesting that Corythosaurus fed on all of these.

Two species of Corythosaurus are recognized, and they are found in slightly different levels of the Dinosaur Park Formation. Both species lived alongside theropods and other ornithischians, including Daspletosaurus, Brachylophosaurus, Parasaurolophus, Scolosaurus, and Chasmosaurus.

The first specimen, AMNH 5240, was discovered in 1911 by Barnum Brown along the Red Deer River in Alberta, and he secured it in the fall of 1912. Besides being an almost complete skeleton, the find was notable because impressions of much of the creature's skin had survived. The specimen came from the Belly River Group. The left side or underside of the skeleton was preserved in carbonaceous clay, which made it difficult to expose the skin to the elements. The skeleton was articulated and missing only about the last part of the tail and the front legs. Both scapulae and coracoids were preserved in position, but the rest of the front legs were gone except for some phalanges and pieces of the humeri, ulnae, and radii. The missing front legs apparently weathered or eroded away. Impressions of the integument covered a large part of the skeleton's outline, showing the form of the body. Another specimen, AMNH 5338, was found in 1914 by Brown and Peter Kaisen. Both specimens are now housed in the American Museum of Natural History in their original death poses.

The type species, Corythosaurus casuarius, was named by Barnum Brown in 1914, based on the first specimen he collected in 1912, making AMNH 5240 the holotype. In 1916, Brown published a more detailed description that also relied on AMNH 5338, which is therefore the plesiotype. Corythosaurus is one of many lambeosaurines with crests, and the crest is what gave the genus its name. The generic name comes from the Greek word for "Corinthian helmet," meaning "helmeted lizard." The specific name, casuarius, refers to the cassowary, a bird with a similar skull crest. So the full binomial Corythosaurus casuarius means "Cassowary-like reptile with a Corinthian helmet crest."

Two of the best-preserved Corythosaurus specimens, found by Charles H. Sternberg in 1912, were lost on December 6, 1916, while being carried by the SS Mount Temple to the United Kingdom during World War I. They were being sent to Arthur Smith Woodward, a paleontologist at the British Museum of Natural History in England, when the ship was sunk by a German merchant raider in the middle of the ocean.

Up to seven species were once described, including C. casuarius, C. bicristatus, C. brevicristatus, C. excavatus, C. frontalis, and C. intermedius. In 1975, Peter Dodson studied differences in the skulls and crests of various lambeosaurine dinosaurs and concluded that the differences in size and shape might actually be related to the sex and age of the animal. Only one species, C. casuarius, is currently recognized for certain, though some studies have considered C. intermedius valid. C. intermedius is based on specimen ROM 776, a skull found by Levi Sternberg in 1920 and named by William Parks in 1923. Parks originally named it Stephanosaurus intermedius earlier that year. The specific name intermedius comes from its apparent intermediate position, according to Parks. C. intermedius lived slightly later in the Campanian than C. casuarius, and the two species are not identical, which supported their separation in a 2009 study. The invalid species C. excavatus (specimen UALVP 13) was based only on a skull found in 1920 and was not reunited with the rest of its remains until 2012.

Benson et al. (2012) estimated that Corythosaurus had an average length. In 1962, Edwin H. Colbert used models of specific dinosaurs, including Corythosaurus, to estimate their weight. The Corythosaurus model was made by Vincent Fusco after a mounted skeleton and supervised by Barnum Brown. After testing, it was concluded that the average weight of Corythosaurus was a certain value. The total length of specimen AMNH 5240 was found to be a specific length, with a weight close to that value. In 2016, Gregory S. Paul estimated that C. casuarius reached a certain size.