Its most recognizable feature is a small solid crest formed by the nasal bones, sticking up in front of the eyes.

Well-known paleontologist Barnum Brown recovered a duckbill skull in 1915 for the American Museum of Natural History (AMNH 5836) from the Red Deer River of Alberta, near Steveville.

He interpreted P. blackfeetensis as having a steeper, taller face than P. maximus, with the crest migrating backward toward the eyes during growth.

[12] This crest grew isometrically (i.e. without changing in proportion) throughout the lifetime of the individual, leading to speculation that the species may have had a soft tissue display structure, such inflatable nasal sacs.

Half of the skull was badly weathered at the time of examination, and the level of the parietal was distortedly crushed upwards to the side.

[4] The unique feature of a shortened frontal in lambeosaurines is also found in Prosaurolophus, and the other horned hadrosaurines Brachylophosaurus, Maiasaura, and Saurolophus.

However, this is contentious; some authors have found the animals to be closely related,[15][16][17] whereas others have not, instead finding it closer to Brachylophosaurus, Edmontosaurus, Gryposaurus, and Maiasaura.

The group contained hadrosaurids with a "males with median horn-like protuberance on the skull" and "very numerous teeth", found by Nopsca to be Parasaurolophus, Saurolophus, and Prosaurolophus.

[3] Young (1958) found that the subfamily Saurolophinae, however, was not to be abandoned, and in it placed his new genus Tsintaosaurus, as well as Prosaurolophus and Saurolophus, and also Kritosaurus (which included Gryposaurus and excluded K. navajovius).

Saurolophidae was a family in Huene's Hadrosauria, including the genera Prosaurolophus, Saurolophus, and the probably unrelated Bactrosaurus.

Ostrom found that the saurolophines Brachylophosaurus, Prosaurolophus, and Saurolophus all possessed a "pseudonarial crest", a feature which united them, while distinguishing them from hollow-crested lambeosaurines.

[3] Hopson (1975) supported the division of Hadrosauridae into two subfamilies, Hadrosaurinae and Lambeosaurinae, and was first to suspect what modern analyses find.

The below cladogram was the one recovered by their analysis:[17] Acristravus gagstarsoni Brachylophosaurus canadensis Maiasaura peeblesorum Shantungosaurus giganteus Edmontosaurus regalis Edmontosaurus annectens Kerberosaurus manakini Sabinas OTU Prosaurolophus maximus Saurolophus morrisi Saurolophus osborni Saurolophus angustirostris Wulagasaurus dongi Kritosaurus navajovius ‘’Aquilarhinus’’ Secernosaurus koerneri Willinakaqe salitralensis Gryposaurus latidens Gryposaurus notabilis Gryposaurus monumentensis In 2001, Prosaurolophus was studied with other hadrosaurids by Wagner.

[3] As a hadrosaurid, Prosaurolophus would have been a large herbivore, eating plants with a sophisticated skull that permitted a grinding motion analogous to chewing.

[7] Comparisons between the scleral rings of Prosaurolophus and modern birds and reptiles suggest that it may have been cathemeral, active throughout the day at short intervals.

These postulated diverticula would have taken the form of inflatable soft-tissue sacs housed in the deep excavations flanking the crest and elongate holes for the nostrils.

[19] The Dinosaur Park Formation, home to Prosaurolophus maximus, is interpreted as a low-relief setting of rivers and floodplains that became more swampy and influenced by marine conditions over time as the Western Interior Seaway transgressed westward.

[22] The roughly contemporaneous Two Medicine Formation, home to P. maximus,[2] is well known for its fossils of dinosaur nests, eggs, and young, produced by the hadrosaurids Hypacrosaurus stebingeri and Maiasaura, and the troodontid Troodon.

[2] Prosaurolophus maximus itself lived in coastal floodplains and dined on conifer trees, implying that it was more likely a browser rather than a grazer.