has suggested that even though it possesses a unique crest, Olorotitan is Corythosaurus closest known relative. Benson et al. (2012) found that Corythosaurus was closely related to Velafrons, Nipponosaurus, and Hypacrosaurus, and said that they formed a group of fan-crested lambeosaurines. In 2014, a study including the description of Zhanghenglong was published in the journal PLOS ONE. The study included an almost complete cladogram of hadrosauroid relationships, including Corythosaurus as the most derived lambeosaurine, as sister taxon to Hypacrosaurus. The below cladogram is a simplified version including only Lambeosaurini. Paleobiology Comparisons between the scleral rings of Corythosaurus and modern birds and reptiles suggest that it may have been cathemeral, active throughout the day at short intervals. The sense of hearing in hadrosaurids, specifically such as Lophorhothon, also seems to have been greatly developed because of an elongated lagena. The presence of a thin stapes (an ear bone that is rod-like in reptiles), combined with a large eardrum implies the existence of a sensitive middle ear. It is possible that hadrosaurid ears are sensitive enough to detect as much sound as a modern crocodilian. Crest function The internal structures of the crest of Corythosaurus are quite complex, making possible a call that could be used for warning or attracting a mate. Nasal passageways of Corythosaurus, as well as Hypacrosaurus and Lambeosaurus are S-shaped, with Parasaurolophus only possessing U-shaped tubes. Any vocalization would travel through these elaborate chambers, and probably get amplified. Scientists speculate that Corythosaurus could make loud, low pitched cries "like a wind or brass instrument", such as a trombone. The sounds could serve to alert other Corythosaurus to the presence of food or a potential threat from a predator. The nasal passages emit low-frequency sounds when Corythosaurus exhaled. The individual crests would produce different sounds, so it is likely that each species of lambeosaurine would have had a unique sound. However, even though the range for different lambeosaurine nasal passages vary, they all probably made low-pitched sounds. This might be because low sounds (below 400 Hz) travel a set distance in any environment, while higher (above 400 Hz) sounds have a larger spread in the distance travelled. When they were first described, crested hadrosaurs were thought to be aquatic, an assessment based incorrectly on webbing that is now known to be padding. The theory was that the animals could swim deep in the water, and use the crest to