Parasaurolophus (/ˌpærəsɔːˈrɒləfəs, -ˌsɔːrəˈloʊfəs/; meaning "near crested lizard" in reference to Saurolophus) is a genus of herbivorous hadrosaurid ornithopod dinosaur that lived in what is now North America and possibly Asia during the Late Cretaceous Period, about 76.5–73 million years ago.[2] It was a herbivore that walked both as a biped and as a quadruped. Three species are universally recognized: P. walkeri (the type species), P. tubicen, and the short-crested P. cyrtocristatus. Additionally, a fourth species, P. jiayinensis, has been proposed, although it is more commonly placed in the separate genus Charonosaurus. Remains are known from Alberta (Canada), New Mexico and Utah (United States), and possibly Heilongjiang (China). The genus was first described in 1922 by William Parks from a skull and partial skeleton found in Alberta.
Parasaurolophus was a hadrosaurid, part of a diverse family of Cretaceous dinosaurs known for their range of bizarre head adornments which were likely used for communication and better hearing. This genus is known for its large, elaborate cranial crest, which at its largest forms a long curved tube projecting upwards and back from the skull. Charonosaurus from China, which may have been its closest relative, had a similar skull and potentially a similar crest. Visual recognition of both species and sex, acoustic resonance, and thermoregulation have been proposed as functional explanations for the crest. It is one of the rarer hadrosaurids, known from only a handful of good specimens.
Meaning "near crested lizard", the name Parasaurolophus is derived from the Greek para/παρα "beside" or "near", saurus/σαυρος "lizard" and lophos/λοφος "crest".[3] It is based on ROM 768, a skull and partial skeleton missing most of the tail and the hind legs below the knees, which was found by a field party from the University of Toronto in 1920 near Sand Creek along the Red Deer River in Alberta, Canada.[4] These rocks are now known as the Campanian-age Upper Cretaceous Dinosaur Park Formation. William Parks named the specimen P. walkeri in honor of Sir Byron Edmund Walker, chairman of the Board of Trustees of the Royal Ontario Museum.[4] Parasaurolophus remains are rare in Alberta,[5] with only one other partial skull from (probably) the Dinosaur Park Formation,[6] and three Dinosaur Park specimens lacking skulls, possibly belonging to the genus.[5] In some faunal lists, there is a mention of possible P. walkeri material in the Hell Creek Formation of Montana, a rock unit of late Maastrichtian age.[7] This occurrence is not noted by Sullivan and Williamson in their 1999 review of the genus,[8] and has not been further elaborated upon elsewhere.
In 1921, Charles H. Sternberg recovered a partial skull (PMU.R1250) from what is now known as the slightly younger Kirtland Formation in San Juan County, New Mexico. This specimen was sent to Uppsala, Sweden, where Carl Wiman described it as a second species, P. tubicen, in 1931.[9] The specific epithet is derived from the Latin tǔbǐcěn "trumpeter".[10] A second, nearly complete P. tubicen skull (NMMNH P-25100) was found in New Mexico in 1995. Using computed tomography of this skull, Robert Sullivan and Thomas Williamson gave the genus a monographic treatment in 1999, covering aspects of its anatomy and taxonomy, and the functions of its crest.[8] Williamson later published an independent review of the remains, disagreeing with the taxonomic conclusions.[11]