page_title: Corythosaurus
section_title: Skull
hierarchical_section_title: Corythosaurus / Description / Skull
caption_attribution_description: English: Corythosaurus skull from the American Museum of Natural History
context_page_description: Corythosaurus is a genus of hadrosaurid "duck-billed" dinosaur from the Upper Cretaceous Period, about 77–75.7 million years ago. It lived in what is now North America. Its name means "helmet lizard", derived from Greek κόρυς. It was named and described in 1914 by Barnum Brown. Corythosaurus is now thought to be a lambeosaurine, related to Nipponosaurus, Velafrons, Hypacrosaurus, and Olorotitan. Corythosaurus has an estimated length of 9 metres, and has a skull, including the crest, that is 70.8 centimetres tall.
  Corythosaurus is known from many complete specimens, including the nearly complete holotype found by Brown in 1911. The holotype skeleton is only missing the last section of the tail, and part of the forelimbs, but was preserved with impressions of polygonal scales. Corythosaurus is known from many skulls with tall crests. The crests resemble the crests of the cassowary and a Corinthian helmet. The most likely function of the crest is thought to be vocalization. As in a trombone, sound waves would travel through many chambers in the crest, and then get amplified when Corythosaurus exhaled. A Corythosaurus specimen has been preserved with its last meal in its chest cavity.
context_section_description: Over twenty skulls have been found from this dinosaur. As with other lambeosaurines, the animal bore a tall, elaborate bony crest atop its skull, which contained the elongate narial passages. The narial passages extended into the crest, first into separate pockets in the sides, then into a single central chamber and onward into the respiratory system. The skull of the type specimen has no dermal impressions on it. During preservation it was compressed laterally, so now the width is about two-thirds what it would have been in real life. According to Brown, the compression also caused the nasals to shift where they pressed down on the premaxillaries. Because they were pressed on the premaxillaries, the nasals would have closed the nares. Apart from the compression, the skull appears to be normal. Contrary to what Brown assumed, the areas concerned were fully part of the praemaxillae.
  The crests of Corythosaurus resemble that of a cassowary, or a Corinthian helmet. They are formed by a combination of the praemaxillae, nasals, prefrontals and frontals, as in Saurolophus, but instead of projecting backwards as a spine, they rise up to make the highest point above the orbit. The two halves of the crest are separated by a median suture. In front of the orbit, the crest is made of thick bone.
  The nasals make up most of the crest. Brown assumed that they extended from the beaks' tip to the highest spot along the crest and that, unlike those in other genera, the nasals meet in the centre and are not separated in front by an ascending premaxillary process. Brown however, mistook the praemaxillae for the nasals; the snout is actually largely formed by them and they do separate the nasals. Brown also thought that on the top and back of the crest, the whole external face is covered by the frontals. Again he made a mistake: what he assumed to be the frontals are in fact the nasals. The nasals end at the back of the squamosals in a hooked, short process. The prefrontals also make up part of the crest; however, Brown mistook the lower upper branch of the praemaxilla for the prefrontal. The actual prefrontal, triangular in shape, is located at the side of the crest base; it was by Brown seen as a part of the frontal. The real frontals, largely internal to the crest base structure, are not visible from the side.
  The mouth of the holotype of Corythosaurus is narrow. The praemaxillae each form two long folds. The folds enclose air passages extending the narial passages to the front of the snout. There they end in narrow openings, sometimes called "pseudonares", false bony nostrils. These were mistaken by Brown for the real nares or nostrils. These are actually situated inside the crest, above the eye sockets. As in Saurolophus, the expanded portion of the premaxillary in front of the pseudonaris' opening is elongate: by comparison, in Kritosaurus, the bill is short, and the pseudonares extend far forward. At the end of the Corythosaurus bill, the two pseudonares unite into one. Because of his incorrect identification, Brown assumed that the holotype's inferior process of the premaxillary was shorter than in Kritosaurus and Saurolophus, and that the process does not unite with the lacrimal, another difference from those genera. The praemaxilla actually does touch the lacrimal and extends to the rear until well behind the eye socket.
  The lower jaw of the holotype is 66.9 centimetres (26.3 in) long, and 10 centimetres (3.9 in) deep. The total length of the crest from the beak to the uppermost tip of the type specimen is 83.7 centimetres (33.0 in), its total length is 81.2 centimetres (32.0 in), and height 70.8 centimetres (27.9 in).
caption: Skull of the type specimen
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