Brachylophosaurus (/brəˌkɪləfəˈsɔːrəs/ brə-KIL-ə-fə-SOR-əs or /ˌbrækiˌloʊfəˈsɔːrəs/ brak-i-LOH-fə-SOR-əs) is a genus of hadrosaurid dinosaur that lived during the Late Cretaceous period of western North America.

[4] In 1936, American paleontologist Charles Mortram Sternberg led an expedition of the Geological Survey of Canada to the region of Dinosaur Provincial Park, Alberta, collecting multiple specimens for the Canadian Museum of Nature including a skull and partial skeleton of a hadrosaur (CMN 8893).

[5] This specimen was found in a thin sandstone bed of the Oldman Formation 0.5 mi (0.80 km) above the mouth of Little Sandhill Creek[a] on the Red Deer River, 60 ft (18 m) above the water level.

58, and though he marked it with a stake and identified it on a map, it was lost for more than 20 years as the back wall had collapsed and buried the marker, only being rediscovered in 2001 and officially designated Q103.

[1] The genus name is derived from the Ancient Greek words βραχύς (brachys), λόφος (lophos), and σαῦρος (sauros), meaning "short", "crest", and "lizard".

Horner named it Brachylophosaurus goodwini in honor of Goodwin, separating it from B. canadensis by multiple features of the skull, and also recognizing that it may eventually be identified as a new genus.

It was uncatalogued at the Field Museum until 1972 when it received the number FMNH PR 862, and though it was identified as material of Brachylophosaurus by American paleontologist James A. Hopson before being loaned to David B. Weishampel from 1980 to 2006, it was Horner's 1988 paper that first published the identification.

However, a second well-preserved specimen has been found in southern Alberta in the area of Manyberries and Onefour, collected by the Royal Tyrrell Museum of Paleontology as TMP 1990.104.1.

[11] A single maxilla from the upper Wahweap Formation of Utah has been tentatively attributed to Brachylophosaurus based on greater similarity than other hadrosaurines, and its equivalent age to material from Judith River.

[12] In the lower Judith River Formation, excavations of the Museum of the Rockies in the mid-1990s uncovered a nearly complete and articulated skeleton in isolation, as well as an extensive bonebed containing hundreds of bones from individuals of all ages.

[13] MOR 794 was discovered in 1994 by fossil collector Nate Murphy on a hillside 15 mi (24 km) north of Malta, preserved in three dimensions without any flattening.

[13] The synonymy of B. goodwini is not unanimous however, as because it lacks the diagnostic nasal crest, it cannot be compared easily with taxa such as Probrachylophosaurus and may be more appropriately considered a dubious member of Brachylophosaurini rather than a synonym of Brachylophosaurus.

On July 20, 2000, a volunteer of the Judith River Dinosaur Institute located a partially exposed pelvis in northern Phillips County, Montana, which was then excavated in 2001.

[18] In May 2008, Steven Cowan, public-relations coordinator at the Houston Museum of Natural Science, discovered a Brachylophosaurus skeleton subsequently dubbed "Marco" from the same area as Leonardo.

Other notable features are a relatively small head, the unusually long lower arms and the beak of the upper jaw being wider than other hadrosaurs of that time.

These "mummies" actually consist of natural casts formed in moulds in the stone matrix surrounding the skeleton, preserving the outline of the body and showing skin imprints.

[24] The following cladogram of hadrosaurid relationships was published in 2013 by Alberto Prieto-Márquez et al.:[25] 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 2003, evidence of tumors, including hemangiomas, desmoplastic fibroma, metastatic cancer, and osteoblastoma was discovered in fossilized Brachylophosaurus skeletons.

[26] A 2008 study conducted on the famous dinosaur mummy Leonardo found that Brachylophosaurus had a diet that consisted of leaves, conifers, ferns, algae, liverworts, and flowering plants like magnolias.