Corythosaurus

Corythosaurus, a duck-billed dinosaur from the hadrosaurid family, 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 in 1914 by Barnum Brown. Today, Corythosaurus is classified as a lambeosaurine, placing it in the same group as Lambeosaurus, Nipponosaurus, Velafrons, Hypacrosaurus, and Olorotitan. While its total length is estimated, its skull, including the tall crest, reaches a notable height.

Many complete Corythosaurus specimens have been found, including the nearly complete holotype discovered by Brown in 1911. That skeleton is missing only the last part of the tail and some front leg bones, but it preserved impressions of polygonal scales. Numerous skulls show tall crests that resemble those of a cassowary or a Corinthian helmet. The crest likely functioned in vocalization: like a trombone, sound waves traveled through chambers in the crest and were amplified when the animal exhaled. One specimen even preserved its last meal in the chest cavity, containing conifer needles, seeds, twigs, and fruits, suggesting Corythosaurus ate all of these.

Two species of Corythosaurus are recognized, each found in slightly different layers of the Dinosaur Park Formation. Both coexisted with theropods and other ornithischians such as 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 secured by him in the fall of 1912. Besides being an almost complete skeleton, it was notable for preserving impressions of much of the creature's skin. The specimen came from the Belly River Group. The left side or underside of the skeleton was embedded in carbonaceous clay, making it difficult to expose the skin. The skeleton was articulated, missing only about the last part of the tail and the front legs. Both scapulae and coracoids were in place, but the rest of the front legs were gone except for some phalanges and pieces of the humeri, ulnae, and radii—apparently weathered or eroded away. Skin impressions covered much of the skeleton's outline, showing the body's form. Another specimen, AMNH 5338, was found in 1914 by Brown and Peter Kaisen. Both are now housed at 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 also based on AMNH 5338, which is therefore the plesiotype. Corythosaurus is among many lambeosaurines with crests, and the crest 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 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 shipped on the SS Mount Temple to the United Kingdom during World War I. They were being sent to paleontologist Arthur Smith Woodward of the British Museum of Natural History 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 skulls and crests among lambeosaurines and concluded that size and shape differences might relate to sex and age. Only one species, C. casuarius, is currently recognized for certain, though some studies consider C. intermedius valid. That species 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 reflects its apparent intermediate position. C. intermedius lived slightly later in the Campanian than C. casuarius, and the two are not identical, supporting 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 Corythosaurus has an average length. In 1962, Edwin H. Colbert used models of specific dinosaurs, including Corythosaurus, to estimate weight. The Corythosaurus model, made by Vincent Fusco after a mounted skeleton and supervised by Barnum Brown, gave an average weight. The total length of specimen AMNH 5240 was found to be a certain length, with a weight close to that estimate. In 2016, Gregory S. Paul estimated that C. casuarius reached a certain size.