page_title: Prosaurolophus
section_title: History of classification
hierarchical_section_title: Prosaurolophus / Classification / History of classification
caption_attribution_description: Prosaurolophus panel mount
context_page_description: Prosaurolophus is a genus of hadrosaurid dinosaur from the Late Cretaceous of North America. It is known from the remains of at least 25 individuals belonging to two species, including skulls and skeletons, but it remains obscure. Around 9 m, its fossils have been found in the late Campanian-age Upper Cretaceous Dinosaur Park Formation in Alberta, and the roughly contemporaneous Two Medicine Formation in Montana, dating to around 75.5-74.0 million years ago. Its most recognizable feature is a small solid crest formed by the nasal bones, sticking up in front of the eyes.
  The type species is P. maximus, described by American paleontologist Barnum Brown of the American Museum of Natural History in 1916. A second species, P. blackfeetensis, was described by Jack Horner of the Museum of the Rockies in 1992. The two species were differentiated mainly by crest size and skull proportions.
context_section_description: In 1918, Lawrence Lambe revised the classifications of Hadrosauridae (then Trachodontidae). He invalidated the family name and Trachodontinae, replacing them with Hadrosauridae and Hadrosaurinae. The other subfamily in Hadrosauridae then was Saurolophinae, which included Stephanosaurus (= Lambeosaurus), Cheneosaurus, Corythosaurus, Prosaurolophus, and Saurolophus. Lambe, in 1920, split Saurolophinae and found only two genera remaining in it, Prosaurolophus, and the type genus. The previous genera were then reclassified into Stephanosaurinae or Hadrosaurinae. In 1928, Prosaurolophus was assigned to Saurolophinae by Franz Nopcsa. 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.
  In 1954, Charles Sternberg reevaluated the genera in Hadrosauridae, invoking the probability that Saurolophinae should be sunk into Hadrosaurinae. This greatly changed the classifications of the family, as the "saurolophines" were kept separate because of their supposedly "footed" ischium. Sternberg identified that the "footed" ischium assigned to Saurolophus was not found with the holotype, and was only assigned to it because of the location of the find. Also, he noted that William Parks (1924) found a complete skeleton of Prosaurolophus clearly showing an "unfooted" ischium, which Sternberg realized meant that it was unlikely that Saurolophus possessed a "footed" ischium. Sternberg's reevaluation led to the abandonment of Saurolophinae.
  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). Two years previous, Friedrich von Huene separated Saurolophinae from Hadrosauridae, naming Saurolophidae. Saurolophidae was a family in Huene's Hadrosauria, including the genera Prosaurolophus, Saurolophus, and the probably unrelated Bactrosaurus. Another author to support the separation of Saurolophinae was John Ostrom (1961). 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.
  Hopson (1975) supported the division of Hadrosauridae into two subfamilies, Hadrosaurinae and Lambeosaurinae, and was first to suspect what modern analyses find. Hopson found that Hadrosaurinae could clearly be divided into groups, the "kritosaurs", the "edmontosaurs", and the "saurolophines", including Prosaurolophus, Saurolophus, Tsintaosaurus and Lophorhothon, and intermediate between the "kritosaurs" and "saurolophines". Brett-Surman (1975) also followed Sternberg with sinking Saurolophinae into Hadrosaurinae, and like Hopson, he recognized three groups within the subfamily. Like Hopson, one group was called the Edmontosaurus lineage, the second the Kritosaurus group, and the third uniting Prosaurolophus and Saurolophus. Over a decade later in 1989, Brett-Surman scientifically named the groups of hadrosaurines, the first becoming Edmontosaurini, the second Kritosaurini, and the third Saurolophini.
caption: Panel mounted cast replica, Stewart Museum of Paleontology
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