''Prosaurolophus'' (; meaning "before ''

Saurolophus ''Saurolophus'' (; meaning "lizard crest") is a genus of large hadrosaurid dinosaur from the Late Cretaceous period of Asia and North America, that lived in what is now the Horseshoe Canyon and Nemegt formations about 70 million to 66 million ...

''", in comparison to the later dinosaur with a similar head crest) is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

hadrosaur Hadrosaurids (), also hadrosaurs or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod fami ...

id (or duck-billed)

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. It is known from the remains of at least 25 individuals belonging to two species, including skulls and skeletons, but it remains obscure. Its fossils have been found in the

late Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian ...

-age

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cret ...

Dinosaur Park Formation The Dinosaur Park Formation is the uppermost member of the Belly River Group (also known as the Judith River Group), a major geologic unit in southern Alberta. It was deposited during the Campanian stage of the Late Cretaceous, between about 7 ...

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

, and the roughly contemporaneous

Two Medicine Formation The Two Medicine Formation is a geological formation, or rock body, in northwestern Montana and southern Alberta that was deposited between 82.4 Ma and 74.4 Ma, during Campanian (Late Cretaceous) time. It crops out to the east of the Rocky Mountai ...

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

, dating to around 75.5-74.0 million years ago. Its most recognizable feature is a small solid crest formed by the

nasal bone The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose. Eac ...

s, sticking up in front of the eyes. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''P. maximus'', described by American paleontologist

Barnum Brown Barnum Brown (February 12, 1873 – February 5, 1963), commonly referred to as Mr. Bones, was an American paleontologist. He discovered the first documented remains of ''Tyrannosaurus'' during a career that made him one of the most famous fossil ...

of the

American Museum of Natural History The American Museum of Natural History (AMNH) is a natural history museum on the Upper West Side of Manhattan in New York City. Located in Theodore Roosevelt Park, across the street from Central Park, the museum complex comprises 21 interconn ...

in 1916. A second species, ''P. blackfeetensis'', was described by

Jack Horner Jack Horner may refer to: *"Little Jack Horner", a nursery rhyme People * Jack Horner (activist) (born 1922), Australian author and activist in the Aboriginal-Australian Fellowship * Jack Horner (baseball) (1863–1910), American professional ba ...

of the

Museum of the Rockies Museum of the Rockies is a museum in Bozeman, Montana. Originally affiliated with Montana State University - Bozeman, Montana State University in Bozeman, and now also, the Smithsonian Institution. The museum is largely known for its Paleontology, ...

in 1992. The two species were differentiated mainly by crest size and skull proportions.

History of discovery

Well-known

paleontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...

Barnum Brown recovered a duckbill skull in 1915 for the

(AMNH 5836) from the

Red Deer River The Red Deer River is a river in Alberta and a small portion of Saskatchewan, Canada. It is a major tributary of the South Saskatchewan River and is part of the larger Saskatchewan / Nelson River, Nelson system that empties into Hudson Bay. T ...

of Alberta, near

Steveville Steveville is a ghost town in southeastern Alberta, Canada near Brooks. In 1910, the community had a general store. Named after Steve Hall, a local homesteader, the community never attracted a large population. The Hall family operated a number ...

. He described the specimen in 1916 as a new genus, ''Prosaurolophus''. Brown's choice of name comes from a comparison to the genus ''Saurolophus'', which he had described in 1912. ''Saurolophus'' had a similar but longer and more spike-like head crest. The skull had a damaged muzzle and was inadvertently reconstructed too long, but better remains were soon found that showed the true shape; one is a nearly complete skeleton and skull, described by William Parks in 1924. Twenty to twenty-five individuals are known for this species, including seven skulls with at least some of the rest of the skeleton. The second species, ''P. blackfeetensis'', is based on a specimen in the Museum of the Rockies (MOR 454), which was described by another notable paleontologist, Jack Horner. This specimen, and the remains of three or four other individuals, were found in Glacier County, Montana. In this case, the fossils were found in a

bonebed A bone bed is any geological stratum or deposit that contains bones of whatever kind. Inevitably, such deposits are sedimentary in nature. Not a formal term, it tends to be used more to describe especially dense collections such as Lagerstätte. ...

of ''Prosaurolophus'' remains, which indicates that the animals lived together for at least some time. The bonebed is interpreted as reflecting a group of animals that congregated near a water source during a drought. Horner differentiated the two species by details of the crest. He interpreted ''P. blackfeetensis'' as having a steeper, taller face than ''P. maximus'', with the crest migrating backward toward the eyes during growth. More recent studies have regarded the differences as insufficient to support two species.

Description

''Prosaurolophus'' was a large-headed duckbill; the most complete described specimen has a skull around long with its body size measuring in length and in body mass. It had a small, stout, triangular crest in front of the eyes; the sides of this crest were concave, forming depressions. 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. When originally described by Brown, ''Prosaurolophus maximus'' was known from a skull and jaw. 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. The different bones of the skull could be easily defined, with the exception of the parietals and

s. Brown found that the skull of the already described genus ''Saurolophus'' is very similar overall to, but also smaller than the skull of ''P. maximus''. The unique feature of a shortened frontal in

lambeosaurines Lambeosauridae /ˌlæmbiəˈsɔːraɪniː/ (meaning 'lambe's lizards') is an extinct group of crested hadrosauroid dinosaurs. Description Size Uncertainty surrounds the size of lambeosaurs from the European continent. Hadrosaurs found there, a ...

is also found in ''Prosaurolophus'', and the other horned hadrosaurines ''

Brachylophosaurus ''Brachylophosaurus'' ( or ) is a genus of hadrosaurid dinosaur that lived during the Late Cretaceous period of western North America. It was first named in 1953 by Charles Mortram Sternberg for a skull and skeleton he discovered in 1936 in th ...

'', ''

Maiasaura ''Maiasaura'' (from the Greek ''μαῖα'', meaning "midwife" and ''σαύρα'', the feminine form of ''saurus'', meaning "reptile") is a large herbivorous saurolophine hadrosaurid ("duck-billed") dinosaur genus that lived in the area currently ...

'', and ''

''. Although they lack a shorter frontal, the genera ''

Edmontosaurus ''Edmontosaurus'' ( ) (meaning "lizard from Edmonton"), with the second species often colloquially and historically known as ''Anatosaurus'' or ''Anatotitan'' (meaning "duck lizard" and "giant duck"), is a genus of hadrosaurid (duck-billed) din ...

'' and ''

Shantungosaurus ''Shantungosaurus'' (meaning "''Shandong Lizard''") is a genus of very large saurolophine hadrosaurid dinosaur found in the Late Cretaceous Wangshi Group of the Shandong Peninsula in China, containing a single species, ''Shantungosaurus gigante ...

'' share with saurolophins an elongated

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

Patches of preserved skin are known from two juvenile specimens,

TMP TMP may refer to: Arts and media * Tickle Me Pink, a rock band from Colorado, US (2005–2011) * Tiny Moving Parts, an emo band from Minnesota, US * Tom Malone Prize, an Australian glass art prize * Tsukuyomi -Moon Phase-, a 2000–2008 anime ...

1998.50.1 and TMP 2016.37.1; these pertain to the ventral extremity of the ninth through fourteenth dorsal ribs, the caudal margin of the scapular blade, and the pelvic region. Small basement scales (scales which makeup the majority of the skin surface), in diameter, are preserved on these patches - this is similar to the condition seen in other saurolophine hadrosaurs. More uniquely, feature scales (larger, less numerous scales which are interspersed within the basement scales) around wide and long are found interspersed in the smaller scales in the patches from the ribs and scapula (they are absent from the pelvic patches). Similar scales are known from the tail of the related ''

Saurolophus angustirostris ''Saurolophus'' (; meaning "lizard crest") is a genus of large hadrosaurid dinosaur from the Late Cretaceous period of Asia and North America, that lived in what is now the Horseshoe Canyon and Nemegt formations about 70 million to 66 million ...

'' (on which they have been speculated to indicate pattern), and it is considered likely adult ''Prosaurolophus'' would've retained the feature scales on their flanks like the juveniles.

Classification

Because of its name, ''Prosaurolophus'' is often associated with ''Saurolophus''. However, this is contentious; some authors have found the animals to be closely related, whereas others have not, instead finding it closer to ''Brachylophosaurus'', ''Edmontosaurus'', ''

Gryposaurus ''Gryposaurus'' (meaning "hooked-nosed (Ancient Greek, Greek ''grypos'') lizard"; sometimes incorrectly translated as "griffin (Latin ''gryphus'') lizard") was a genus of hadrosaur, duckbilled dinosaur that lived about 80 to 75 million years ag ...

'', and ''Maiasaura''.

History of classification

In 1918,

Lawrence Lambe Lawrence Morris Lambe (August 27, 1863 – March 12, 1919) was a Canadian geologist, palaeontologist, and ecologist from the Geological Survey of Canada (GSC). His published work, describing the diverse and plentiful dinosaur discoveries from t ...

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 ''Stephanosaurus'' (meaning "crown lizard") is a dubious genus of hadrosaurid dinosaur with a complicated taxonomic history. In 1902, Lawrence Lambe named a new set of hadrosaurid limb material and other bones (originally GSC 419) from Alber ...

'' (= ''

Lambeosaurus ''Lambeosaurus'' ( ) is a genus of hadrosaurid dinosaur that lived during the Late Cretaceous period of western North America. The first skull of ''Lambeosaurus'' found was used by palaeontologist Lawrence M. Lambe to justify the creation of ...

''), '' Cheneosaurus'', ''

Corythosaurus ''Corythosaurus'' (; ) is a genus of hadrosaurid "duck-billed" dinosaur from the Late Cretaceous Period (geology), period, about 77–75.7 million years ago, in what is now Laramidia, western North America. Its name is derived from the Anci ...

'', ''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 Saurolophinae is a subfamily (biology), subfamily of hadrosaurid dinosaurs. It has since the mid-20th century generally been called the Hadrosaurinae, a group of largely non-crested hadrosaurs related to the crested sub-family Lambeosaurinae. How ...

Franz Nopcsa Franz may refer to: People * Franz (given name) * Franz (surname) Places * Franz (crater), a lunar crater * Franz, Ontario, a railway junction and unorganized town in Canada * Franz Lake, in the state of Washington, United States – see Fran ...

. 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 ''Parasaurolophus'' (; meaning "beside crested lizard" in reference to ''Saurolophus'') is a genus of hadrosaurid "duck-billed" dinosaur that lived in what is now western North America and possibly Asia during the Late Cretaceous period, a ...

'', ''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 The ischium (; : is ...

. 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 ''Tsintaosaurus'' (; ''sic'' for the Chinese postal romanization, old transliteration "Tsingtao", meaning "Qingdao lizard") is a genus of Hadrosauridae, hadrosaurid dinosaur from China. It was about long and weighed . The type species is ''Tsin ...

'', as well as ''Prosaurolophus'' and ''Saurolophus'', and also ''Kritosaurus'' (which included ''Gryposaurus'' and excluded ''K. navajovius''). Two years previous,

Friedrich von Huene Baron Friedrich Richard von Hoyningen-Huene (22 March 1875 – 4 April 1969) was a German nobleman paleontologist who described a large number of dinosaurs, more than anyone else in 20th-century Europe. He studied a range of Permo-Carbonife ...

separated Saurolophinae from Hadrosauridae, naming Saurolophidae. Saurolophidae was a family in Huene's Hadrosauria, including the genera ''Prosaurolophus'', ''Saurolophus'', and the probably unrelated ''

Bactrosaurus ''Bactrosaurus'' (; meaning "Club lizard," "baktron" = club + ''sauros'' = lizard) is a genus of herbivorous hadrosauroid dinosaur that lived in Asia during the Late Cretaceous, from about 96 to 85 million years ago. The position ''Bactrosaurus'' ...

''. Another author to support the separation of Saurolophinae was

John Ostrom John Harold Ostrom (February 18, 1928 – July 16, 2005) was an American paleontologist who revolutionized the modern understanding of dinosaurs. Ostrom's work inspired what his pupil Robert T. Bakker has termed a " dinosaur renaissance". Begin ...

(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 ''Lophorhothon'' is a genus of hadrosauroid dinosaur from the Late Cretaceous of Alabama, Georgia (US state), Georgia, and North Carolina. It was the first genus of dinosaur discovered in Alabama, in the United States. Discovery and naming R ...

'', 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 Saurolophinae is a subfamily of hadrosaurid dinosaurs. It has since the mid-20th century generally been called the Hadrosaurinae, a group of largely non-crested hadrosaurs related to the crested sub-family Lambeosaurinae. However, the name Hadros ...

, the second

Kritosaurini Saurolophinae is a subfamily of hadrosaurid dinosaurs. It has since the mid-20th century generally been called the Hadrosaurinae, a group of largely non-crested hadrosaurs related to the crested sub-family Lambeosaurinae. However, the name Hadros ...

, and the third

Saurolophini Saurolophinae is a subfamily of hadrosaurid dinosaurs. It has since the mid-20th century generally been called the Hadrosaurinae, a group of largely non-crested hadrosaurs related to the crested sub-family Lambeosaurinae. However, the name Hadros ...

Phylogeny

The first cladistic analysis to encompass the interrelationships of Hadrosauridae was conducted by Weishampel and Horner (1990). They found Saurolophinae synonymous with Hadrosaurinae, but only separated the subfamily into two groups. The first group included ''Gryposaurus'', ''

Aralosaurus ''Aralosaurus'' was a genus of hadrosaurid dinosaur that lived during the Late Cretaceous in what is now Kazakhstan. It is known only by a posterior half of a skull (devoid of its mandible) and some post-cranial bones found in the Bostobe Format ...

'', ''Maiasaura'', and ''Brachylophosaurus''. The other contained ''Edmontosaurus'', ''Saurolophus'', ''Prosaurolophus'', ''Lophorhothon'', and ''Shantungosaurus''. A detailed cladgram of hadrosaurid relationships was published in 2013 by

Acta Palaeontologica Polonica ''Acta Palaeontologica Polonica'' is a quarterly peer-reviewed open access scientific journal of paleontology and paleobiology. It was established by Roman Kozłowski in 1956. It is published by the Institute of Paleobiology of the Polish Academ ...

. The study was led by Alberto Prieto-Márquez, and recovered ''Prosaurolophus'' in a similar position as suggested by Brown in 1916. The below cladogram was the one recovered by their analysis: Prosaurolophus maximus1

In 2001, ''Prosaurolophus'' was studied with other hadrosaurids by Wagner. The genus, along with ''Corythosaurus'' and ''Maiasaura'', were considered by Wagner to be synonymous with ''Saurolophus'', ''Hypacrosaurus'' and ''Brachylophosaurus'' respectively. ''Prosaurolophus maximus'' was reassigned to ''Saurolophus'' as ''S. maximus''. The same year however, ''Prosaurolophus'' was found to be distinct from ''Saurolophus'', in an analysis of Hu ''et al.''. Their analysis was unique from any of the time, and they recovered ''Prosaurolophus'' in Saurolophinae, with ''Saurolophus'', ''Lophorhothon'', ''Tsintaosaurus'', ''

Jaxartosaurus ''Jaxartosaurus'' (meaning "Jaxartes lizard" after the early name of the Syr Darya) is a genus of hadrosaurid dinosaur similar to ''Corythosaurus'' which lived during the Late Cretaceous. Its fossils were found in Kazakhstan. Discovery The fir ...

'', and ''Kritosaurus''. No other analysis has recovered this group of dinosaurs. Horner ''et al.'' (2004) also recovered a different phylogeny of Saurolophinae. ''Prosaurolophus'' was, for the first time, recovered separate from ''Saurolophus'', in fact not even closely related. ''Prosaurolophus'' was found in a group with ''Brachylophosaurus'', ''Maiasaura'', ''Grpyosaurus'', and ''Edmontosaurus'', while ''Saurolophus'' was grouped with ''

Naashoibitosaurus ''Naashoibitosaurus'' (from Navajo —"creek lizard") is a genus of hadrosaurid dinosaur that lived about 73 million years ago, in the Late Cretaceous, and was found in the Kirtland Formation of the San Juan Basin in New Mexico, United States ...

'' (=''Kritosaurus'') and "Kritosaurus" ''australis''. The ''Prosaurolophus''-''Saurolophus'' clade has been a problematic grouping when trying to place among hadrosaurines. Many skull features are similar to ''Edmontosaurus'', while other are closer to ''Gryposaurus'', so the group has been classified as close to both. However, the clade might be closer to ''Edmontosaurus'', as the features are more numerous uniting them.

Paleobiology

As a hadrosaurid, ''Prosaurolophus'' would have been a large

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

, eating

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

s with a sophisticated skull that permitted a grinding motion analogous to

chewing Chewing or mastication is the process by which food is crushed and ground by the teeth. It is the first step in the process of digestion, allowing a greater surface area for digestive enzymes to break down the foods. During the mastication proc ...

. Its

teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

were continually replaced and packed into

dental batteries Dinosaur teeth have been studied since 1822 when Mary Ann Mantell (1795-1869) and her husband Gideon Algernon Mantell, Dr Gideon Algernon Mantell (1790-1852) discovered an ''Iguanodon'' tooth in Sussex in England. Unlike Mammal tooth, mammal teeth ...

that contained hundreds of teeth, only a relative handful of which were in use at any time. Plant material would have been cropped by its broad beak, and held in the jaws by a

cheek The cheeks () constitute the area of the face below the eyes and between the nose and the left or right ear. ''Buccal'' means relating to the cheek. In humans, the region is innervated by the buccal nerve. The area between the inside of th ...

-like structure. Feeding would have been from the ground up to around 4 meters (13 ft) above. Like other hadrosaurs, it could have moved both

bipedally Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear (or lower) limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' ' ...

and

quadruped Quadrupedalism is a form of locomotion in which animals have four legs that are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four legs is said to be a quadruped (fr ...

ally. Comparisons between the

scleral ring The scleral ring or sclerotic ring is a hardened ring of plates, often derived from bone, that is found in the eyes of many animals in several groups of vertebrates. Some species of mammals, amphibians, and crocodilians lack scleral rings. The ring ...

s of ''Prosaurolophus'' and modern birds and reptiles suggest that it may have been

cathemeral Cathemerality, sometimes called metaturnality, is an organismal activity pattern of irregular intervals during the day or night in which food is acquired, socializing with other organisms occurs, and any other activities necessary for livelihood ...

, active throughout the day at short intervals.

Social behavior

As noted, there is bonebed evidence that this genus lived in groups during at least part of the year. Additionally, it had several potential methods for display in a social setting. The bony facial crest is an obvious candidate, and nasal diverticula may also have been present. These postulated

diverticula In medicine or biology, a diverticulum is an outpouching of a hollow (or a fluid-filled) structure in the body. Depending upon which layers of the structure are involved, diverticula are described as being either true or false. In medicine, t ...

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

nostril A nostril (or naris , : nares ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbinates ...

s. Such sacs could be used for both visual and auditory signals.

Paleoecology

The Dinosaur Park Formation, home to ''Prosaurolophus maximus'', is interpreted as a low-relief setting of

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

s and

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...

s that became more

swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...

y and influenced by marine conditions over time as the

Western Interior Seaway The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, or the Western Interior Sea) was a large inland sea (geology), inland sea that existed roughly over the present-day Great Plains of ...

transgressed westward.Eberth, David A. 2005. "The geology", in ''Dinosaur Provincial Park'', pp. 54–82. The climate was warmer than present-day Alberta, without

frost Frost is a thin layer of ice on a solid surface, which forms from water vapor that deposits onto a freezing surface. Frost forms when the air contains more water vapor than it can normally hold at a specific temperature. The process is simila ...

, but with wetter and drier seasons.

Conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...

s were apparently the dominant

canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an a ...

plants, with an

understory In forestry and ecology, understory (American English), or understorey (English in the Commonwealth of Nations, Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the Canopy (biology), forest ca ...

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

tree fern Tree ferns are arborescent (tree-like) ferns that grow with a trunk (botany), trunk elevating the fronds above ground level, making them trees. Many extant tree ferns are members of the order Cyatheales, to which belong the families Cyatheaceae ( ...

s, and

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s.Braman, Dennis R., and Koppelhus, Eva B. 2005. "Campanian palynomorphs", in ''Dinosaur Provincial Park'', pp. 101–130. In this well-studied formation, ''P. maximus'' is only known from the upper part, which had more of a marine influence than the lower section. It was the most common hadrosaurine of this section, which was deposited about 75.5 million years ago. The Dinosaur Park Formation was also home to well-known dinosaurs like the

horned A horn is a permanent pointed projection on the head of various animals that consists of a covering of keratin and other proteins surrounding a core of live bone. Horns are distinct from antlers, which are not permanent. In mammals, true horns ...

Centrosaurus ''Centrosaurus'' ( ; ) is a genus of centrosaurine ceratopsian dinosaur from Campanian age of Late Cretaceous Canada. Their remains have been found in the Dinosaur Park Formation, dating from 76.5 to 75.5 million years ago. Discovery and nami ...

'', ''

Styracosaurus ''Styracosaurus'' ( ; meaning "spiked lizard" from the Ancient Greek / "spike at the butt-end of a spear-shaft" and / "lizard") is an extinct genus of herbivorous ceratopsian dinosaur from the Late Cretaceous (Campanian stage) of North America. ...

'', and ''

Chasmosaurus ''Chasmosaurus'' ( ) is a genus of ceratopsid dinosaur from the Late Cretaceous Period in North America. Its given name means 'opening lizard', referring to the large openings ( fenestrae) in its frill (Greek ''chasma'', meaning 'opening', 'hol ...

'', fellow duckbills ''Gryposaurus'', ''Corythosaurus'', ''Lambeosaurus'', and ''Parasaurolophus'',

tyrannosaurid Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to fifteen genera, including the eponymous ''Tyrannosaurus''. The exact number of genera ...

Gorgosaurus ''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.5 and 75 million years ago. Fossil remains have been found in the Ca ...

'', and armored ''

Edmontonia ''Edmontonia'' is a genus of panoplosaurin nodosaurid dinosaur from the Late Cretaceous Period. It is part of the Nodosauridae, a family within Ankylosauria. It is named after the Edmonton Formation (now the Horseshoe Canyon Formation in Canada ...

'' and ''

Euoplocephalus ''Euoplocephalus'' ( ) is a genus of large herbivorous ankylosaurid dinosaurs, living during the Late Cretaceous of Canada. It has only one named species, ''Euoplocephalus tutus''. The first fossil of ''Euoplocephalus'' was found in 1897 in Albe ...

''.Weishampel, David B.; Barrett, Paul M.; Coria, Rodolfo A.; Le Loeuff, Jean; Xu Xing; Zhao Xijin; Sahni, Ashok; Gomani, Elizabeth, M.P.; and Noto, Christopher R. (2004). "Dinosaur Distribution", in ''The Dinosauria'' (2nd), pp. 517–606. The roughly contemporaneous Two Medicine Formation, home to ''P. maximus'', is well known for its fossils of dinosaur nests, eggs, and young, produced by the hadrosaurids '' Hypacrosaurus stebingeri'' and ''Maiasaura'', and the

troodontid Troodontidae is a clade of bird-like theropod dinosaurs from the Late Jurassic to Late Cretaceous. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinos ...

Troodon ''Troodon'' ( ; ''Troödon'' in older sources) is a controversial genus of relatively small, bird-like theropod dinosaurs definitively known from the Campanian age of the Late Cretaceous period (about 77 million years ago). It includes at l ...

''. The tyrannosaurid ''

Daspletosaurus ''Daspletosaurus'' ( ; meaning "frightful lizard") is a genus of tyrannosaurid dinosaur that lived in Laramidia between about 77 and 74.4 million years ago, during the Late Cretaceous Period. The genus ''Daspletosaurus'' contains three named ...

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caenagnathid Caenagnathidae is a family of derived caenagnathoid dinosaurs from the Cretaceous of North America and Asia. They are a member of the Oviraptorosauria, and relatives of the Oviraptoridae. Like other oviraptorosaurs, caenagnathids had specialized ...

Chirostenotes ''Chirostenotes'' ( ; named from Ancient Greek, Greek 'narrow-handed') is a genus of oviraptorosaurian dinosaur from the late Cretaceous (about 76.5–75 million years ago) of Alberta, Canada. The type species is ''Chirostenotes pergracilis''. ...

'',

dromaeosaurids Dromaeosauridae () is a family of feathered coelurosaurian theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Gree ...

Bambiraptor ''Bambiraptor'' is a Late Cretaceous, 72-million-year-old, bird-like dromaeosaurid theropod dinosaur described by scientists at the University of Kansas, Yale University, and the University of New Orleans. The holotype fossil is less than one ...

'' and ''

Saurornitholestes ''Saurornitholestes'' ("lizard-bird thief") is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Canada (Alberta and Saskatchewan) and the United States (Montana, New Mexico, Alabama, and South Carolina). Two spe ...

'', armored dinosaurs ''Edmontonia'' and ''Euoplocephalus'',

hypsilophodont Hypsilophodontidae (or Hypsilophodontia) is a traditionally used family of ornithopod dinosaurs, generally considered invalid today. It historically included many small bodied bipedal neornithischian taxa from around the world, and spanning from ...

Orodromeus ''Orodromeus'' (meaning "Mountain Runner") is a genus of herbivorous orodromine thescelosaurid dinosaur from the Late Cretaceous of North America. Only one species is known, the type species ''Orodromeus makelai''. Discovery and naming The re ...

'', and horned dinosaurs ''

Achelousaurus ''Achelousaurus'' () is a genus of Centrosaurinae, centrosaurine ceratopsid dinosaur that lived during the Late Cretaceous, Late Cretaceous Period of what is now North America, about 77 to 74.8 million years ago. The first fossils of ''A ...

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Brachyceratops ''Brachyceratops'' ('short horned face') is a dubious genus of ceratopsian dinosaur known only from partial juvenile specimens dating to the late Cretaceous Period of Montana, United States. ''Brachyceratops'' has historically been known from j ...

'', ''

Einiosaurus ''Einiosaurus'' is a genus of herbivorous centrosaurine ceratopsian dinosaur from the Upper Cretaceous (Campanian stage) of northwestern Montana. The name means 'bison lizard', in a combination of Blackfoot language, Blackfeet Indian ''eini'' and ...

'', and ''

Styracosaurus ovatus ''Styracosaurus'' ( ; meaning "spiked lizard" from the Ancient Greek / "spike at the butt-end of a spear-shaft" and / "lizard") is an extinct genus of herbivorous ceratopsian dinosaur from the Late Cretaceous (Campanian stage) of North America. ...

'' were also present. This formation was more distant from the Western Interior Seaway, and higher and drier than the Dinosaur Park Formation. The age of ''Prosaurolophus maximus'' remains from this formation is from approximately 75.5 to 74.0 million years ago.

Diet

''Prosaurolophus maximus'' itself lived in coastal

floodplains A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high discharge.Goudie, ...

fed on the conifer trees and the

tree bark Bark is the outermost layer of stems and roots of woody plants. Plants with bark include trees, woody vines, and shrubs. Bark refers to all the tissues outside the vascular cambium and is a nontechnical term. It overlays the wood and consist ...

in the area, implying that it was more likely a browser rather than a grazer.

References

{{Taxonbar, from=Q132191 Saurolophinae Dinosaur genera Campanian dinosaurs Dinosaur Park Formation Two Medicine Formation Taxa named by Barnum Brown Fossil taxa described in 1916 Dinosaurs of Canada Dinosaurs of the United States

History of discovery

Description

Classification

History of classification

Phylogeny

Paleobiology

Social behavior

Paleoecology

Diet

See also

References