Brachylophosaurus

Brachylophosaurus (/brəˌkɪləfoʊˈsɔːrəs/ brə-KIL-ə-fo-SAWR-əs or /ˌbrækiˌloʊfəˈsɔːrəs/ brak-i-LOH-fə-SAWR-əs; meaning "short-crested lizard", Greek brachys = short + lophos = crest + sauros = lizard, referring to its small crest) was a mid-sized member of the hadrosaurid family of dinosaurs. It is known from several skeletons and bonebed material from the Judith River Formation of Montana and the Oldman Formation of Alberta,[1] living about 78 million years ago.[2]

Brachylophosaurus
Temporal range: Late Cretaceous, 78 Ma
Roberta Brachylophosaurus
Fossil nicknamed Roberta
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Suborder: Ornithopoda
Family: Hadrosauridae
Subfamily: Saurolophinae
Tribe: Brachylophosaurini
Genus: Brachylophosaurus
Sternberg, 1953
Type species
Brachylophosaurus canadensis
Sternberg, 1953

Description

Size and general build

Brachylophosaurus scale diagram
Scale diagram comparing relative sizes of a nine metres long Brachylophosaurus and human beings

Brachylophosaurus is notable for its bony crest, which forms a horizontally flat, paddle-like plate over the top of the rear skull.[3] Some individuals, depending on their age, had crests that covered nearly the entire skull roof, while others had shorter, narrower crests.[4] Some researchers have suggested it was used for pushing contests,[5][6] but it may not have been strong enough for this. Other notable features are a relatively small head, the unusually long lower arms and the beak of the upper jaw being wider than with other contemporary hadrosaurs.[3]

Apart from the above, Brachylophosaurus was a typical hadrosaur which reached an adult length of at least 9 metres (30 ft).[3] In 2010, Gregory S. Paul estimated maximum length at 11 metres (36 ft) resulting in weight of 7 metric tons (7.7 short tons).[7] Like other hadrosaurs, Brachylophosaurus possessed features like cheeks to keep fodder in the mouth and dental batteries consisting of hundreds of stacked teeth.[3] These teeth could be used to chew efficiently,[3] a feature rare among reptiles, but common among some cerapodan ornithischian dinosaurs like Brachylophosaurus.

Distinguishing traits

Brachylophosaurus NT
Restoration

In 2015, Jack Horner established some distinguishing traits. Two of these are autapomorphies, unique derived characters. The crest formed by the nasal bones is flat and paddle-shaped in adult individuals and largely or totally overhangs the supratemporal fenestrae. The rear edge of the prefrontal bone overgrowths the frontal bone and more to the rear is oriented inwards and downwards to support the base of the crest and contribute to the edge of the supratemporal fenestra. Additionally, there is one trait that is not unique in itself but forms a unique combination with the two autapomorphies: the front branch of the lacrimal bone is extremely elongated and with its tip only touches the maxillary bone.[2]

Skeleton

Brachylophosaurus tail with tendons - Museum of the Rockies
Partial tail with tendons

The head of Brachylophosaurus is elongated. It is wide at the rear and very narrow along most of the length of the snout. The upper beak however, abruptly widens at its rear edge, forming a broad bone core for a horn sheath. The nostrils are extremely large and between them the nasal bones form a narrow tall bone wall on top of much of the snout. More to behind the nasal bones stretch out horizontally, creating a flat tongue-shaped skull crest that overgrowths and ultimately overhangs, most of the skull roof. The crest is not hollow but consists of massive bone. The crest has a low longitudinal ridge on the midline.

The maxilla, the tooth-bearing upper jaw bone, is rather elongated in front. Its tooth positions increase during the lifetime of the animal, ranging from thirty-three in younger individuals to forty-eight in the holotype specimen. The teeth are stacked in a tooth battery, with up to three teeth per position. The battery forms a sharp cutting edge, bending inwards, with one or sometimes two teeth per position contributing to the attrition surface. More to behind, the lower jugal bones and quadrate bones flare out sidewards, so that the skull is much wider at its rear lower edges than at the top surface, resulting in a trapezium-shaped profile in posterior view.

Soft tissues

Leonardo mummified brachylophosaurus
The mummified specimen "Leonardo" in The Children's Museum of Indianapolis

Several so-called "mummies" provide information about the soft tissues of Brachylophosaurus. 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. The best studied "mummy" has been "Leonardo", a specimen 90% of the cast surface of which is covered by imprints. Generally, the surface is close to the bones, which could be caused by desiccation before burial or the compressive action of the covering sediment. An exception is the region around the right shoulder, which shows the profile of about six centimetres thick muscles. "Leonardo" also indicates that the base of the neck was heavily muscled and that the soft tissue upper neck profile was placed in an elevated position, running much higher than was usually reconstructed in drawings which tended to follow the curvature of the vertebral column, and filling much of the bend between the front back and the head.[8]

On the snout, the remains of a broad keratinous beak are visible. The skin impressions show many folds and a structure of small polygonal scales. On the back a midline frill formed by triangular or hatchet-shaped projections is present. These seem to be individually separated and are placed as extensions of each neural spine of the vertebral column. The second, third and fourth finger of the hand are contained in a shared soft tissue "mitten".[8]

Examination of the stomach of "Leonardo" also reveals that the dinosaur was parasitized by small, needle-like worms covered in fine bristles. The discovery indicates that other dinosaur species might have been hosts of similar parasites.[9]

Discovery and later finds

Brachylophosaurus skull
Skull cast of the holotype

Brachylophosaurus was first named and described by Charles Mortram Sternberg in 1953 for a skull and partial skeleton, holotype NMC 8893, which he had found in 1936 near Steveville in Alberta, and which was at first thought to belong to Gryposaurus (or Kritosaurus as it was known at the time). The type species is Brachylophosaurus canadensis. The generic name is derived from Greek βραχύς, brachys, "short", and λόφος, lophos, "crest of a helmet". The specific name refers to the provenance from Canada.[10] Later, it was recognised that specimen FMNH PR 862, a partial skull discovered in 1922, could also be referred to B. canadensis. The type specimen was uncovered in a layer of the middle Oldman Formation dating from about 78 million years ago.[2]

Subadult Brachylophosaurus braincase
Specimen MOR 940 seen from above

The holotype remained the only described and recognised specimen of the genus until the 1980s, when Jack Horner described a second species, Brachylophosaurus goodwini, in 1988. The specific name honours preparator and collector Mark Goodwin. This species was based on a partial skull and skeleton, specimen UCMP 130139 found in the Judith River Formation of Montana, at the Skull Crest.[11] However, in 2005 a study by Albert Prieto-Márquez concluded that the perceived differences between the two species were either due to individual variation or the result of UCMP 130139 having been reconstructed with an upside down skull crest. B. goodwini would have been a junior synonym of B. canadensis.[4]

A further Canadian find was specimen TMP 1990.104.0001, a partial skeleton with skull in 1990 discovered at Milk River in Alberta and collected by Tyrrell staffer Darren Tanke and crew. Brachylophosaurus has subsequently become better known from fossils found in Montana than Alberta, however, despite its specific name canadensis. These include specimens MOR 720, a braincase; MOR 794, a very complete skeleton with skull of an adult individual; and MOR 940, another braincase. Near Malta, Montana an entire bonebed of Brachylophosaurus fossils has been uncovered containing over eight hundred specimens, that have been catalogued under number MOR 1071.[2]

Leonardo dinosaur
Underside of "Leonardo"'s head and neck, showing skin impressions

In 1994 at Malta in Phillips County, amateur paleontologist Nate Murphy discovered a complete and uncrushed Brachylophosaurus skeleton which he nicknamed "Elvis".[12] Subsequently, even more informative finds were made by Murphy and his team from the Judith River Dinosaur Institute. On 20 July 2000, specimen JRF 115H or "Leonardo", a fully articulated and partially "mummified" skeleton of a subadult Brachylophosaurus, was discovered by Dan Stephenson.[8][13] It is considered one of the most spectacular dinosaur finds ever, and was included in the Guinness Book of World Records.[14] They subsequently excavated "Roberta", an almost complete gracile skeleton, and "Peanut", a partially preserved juvenile with some skin impressions. "Peanut" was discovered in 2002 by Robert E. Buresh and is on display at the Institute in Malta, MT.[15] 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.[16]

Classification

The following cladogram of hadrosaurid relationships was published in 2013 by Alberto Prieto-Márquez et al.:[17]

Hadrosaurinae premaxillae
Premaxilla (A), compared to that of other saurolophines
Saurolophinae
Brachylophosaurini

Acristravus gagstarsoni

Brachylophosaurus canadensis

Maiasaura peeblesorum

Shantungosaurus giganteus

Edmontosaurus

Edmontosaurus regalis

Edmontosaurus annectens

Saurolophini

Kerberosaurus manakini

Sabinas OTU

Prosaurolophus maximus

Saurolophus

Saurolophus morrisi

Saurolophus osborni

Saurolophus angustirostris

Kritosaurini

Wulagasaurus dongi

Kritosaurus navajovius

Aquilarhinus

Secernosaurus koerneri

Willinakaqe salitralensis

Gryposaurus

Gryposaurus latidens

Gryposaurus notabilis

Gryposaurus monumentensis

Paleobiology

A-New-Basal-Hadrosauroid-Dinosaur-(Dinosauria-Ornithopoda)-with-Transitional-Features-from-the-Late-pone.0098821.g011
Teeth (F)

In 2003, evidence of tumors, including hemangiomas, desmoplastic fibroma, metastatic cancer, and osteoblastoma was discovered in fossilized Brachylophosaurus skeletons. Rothschild et al. tested dinosaur vertebrae for tumors using computerized tomography and fluoroscope screening. Several other hadrosaurids, including Edmontosaurus, Gilmoreosaurus, and Bactrosaurus, also tested positive. Although more than 10,000 fossils were examined in this manner, the tumors were limited to Brachylophosaurus and closely related genera. The tumors may have been caused by environmental factors or genetic propensity.[18]

Paleoecology

Some of the less common hadrosaurs in the Dinosaur Park Formation of Dinosaur Provincial Park like Brachylophosaurus may represent the remains of individuals who died while migrating through the region.[19] They might also have had a more upland habitat where they may have nested or fed.[19]

See also

Most Closely Related animals

References

  1. ^ Horner, John R.; Weishampel, David B.; Forster, Catherine A (2004). "Hadrosauridae". In Weishampel, David B.; Osmólska, Halszka; Dodson, Peter (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 438–463. ISBN 0-520-24209-2.
  2. ^ a b c d Fowler, Elizabeth A. Freedman, and John R. Horner. "A New Brachylophosaurin Hadrosaur (Dinosauria: Ornithischia) with an Intermediate Nasal Crest from the Campanian Judith River Formation of Northcentral Montana." PLOS One 10.11 (2015): e0141304.
  3. ^ a b c d e "Brachylophosaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. The Age of Dinosaurs. Publications International, LTD. p. 134. ISBN 0-7853-0443-6.
  4. ^ a b Prieto-Marquez, Alberto (2005). "New information on the cranium of Brachylophosaurus, with a revision of its phylogenetic position". Journal of Vertebrate Paleontology. 25 (1): 144–156. doi:10.1671/0272-4634(2005)025[0144:NIOTCO]2.0.CO;2.
  5. ^ Hopson, James A. (1975). "The evolution of cranial display structures in hadrosaurian dinosaurs". Paleobiology. 1 (1): 21–43. doi:10.1017/S0094837300002165.
  6. ^ Weishampel, David B.; Horner, Jack R. (1990). "Hadrosauridae". In Weishampel, David B.; Osmólska, Halszka; Dodson, Peter (eds.). The Dinosauria (1st ed.). Berkeley: University of California Press. pp. 534–561. ISBN 0-520-06727-4.
  7. ^ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 304
  8. ^ a b c Murphy, Nate L.; Trexler, David; Thompson, Mark (2006). ""Leonardo," a mummified Brachylophosaurus from the Judith River Formation". In Carpenter, Kenneth (ed.). Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Bloomington and Indianapolis: Indiana University Press. pp. 117–133. ISBN 0-253-34817-X.
  9. ^ http://www.eartharchives.org/sharebars/409
  10. ^ Sternberg, Charles M. (1953). "A new hadrosaur from the Oldman Formation of Alberta: Discussion of nomenclature". Canadian Department of Resource Development Bulletin. 128: 1–12.
  11. ^ Horner, John R. (1988). "A new hadrosaur (Reptilia, Ornithischia) from the Upper Cretaceous Judith River Formation of Montana". Journal of Vertebrate Paleontology. 8 (3): 314–321. doi:10.1080/02724634.1988.10011714.
  12. ^ "Brachylophosaurus dinosaur discovery". Judith River Dinosaur Institute. 2002. Archived from the original on 2008-09-08. Retrieved 2008-07-13.
  13. ^ "Dear Mummy: Rare fossil reveals common dinosaur's soft tissue: Science News Online". 2002-10-19. Archived from the original on 2007-01-14. Retrieved 2007-07-06.
  14. ^ "Brachylophosaurus dinosaur discovery". Judith River Dinosaur Institute. 2002. Archived from the original on 2008-05-18. Retrieved 2008-07-13.
  15. ^ Newhouse, Eric (2008-06-01). "Malta dinosaur museum read to roar". Great Falls Tribune. Retrieved 2008-07-13.
  16. ^ Newhouse, Eric (2008-06-02). "Badlands yield another impressive fossil". Great Falls Tribune. Retrieved 2008-07-13.
  17. ^ Prieto-Márquez, A.; Wagner, J.R. (2013). "A new species of saurolophine hadrosaurid dinosaur from the Late Cretaceous of the Pacific coast of North America". Acta Palaeontologica Polonica. 58 (2): 255–268. doi:10.4202/app.2011.0049.
  18. ^ Rothschild, B.M.; Tanke, D.H.; Helbling II, M.; Martin, L.D. (2003). "Epidemiologic study of tumors in dinosaurs". Naturwissenschaften. 90 (11): 495–500. doi:10.1007/s00114-003-0473-9. PMID 14610645.
  19. ^ a b Tanke, D.H. and Brett-Surman, M.K. 2001. Evidence of Hatchling and Nestling-Size Hadrosaurs (Reptilia:Ornithischia) from Dinosaur Provincial Park (Dinosaur Park Formation: Campanian), Alberta, Canada. pp. 206-218. In: Mesozoic Vertebrate Life—New Research Inspired by the Paleontology of Philip J. Currie. Edited by D.H. Tanke and K. Carpenter. Indiana University Press: Bloomington. xviii + 577 pp.

External links

1953 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1953.

Acristavus

Acristavus is a genus of saurolophine dinosaur. Fossils have been found from the Campanian Two Medicine Formation in Montana and Wahweap Formation in Utah, United States. The type species A. gagslarsoni was named in 2011. Unlike nearly all hadrosaurids except Edmontosaurus, Acristavus lacked ornamentation on its skull. The discovery of Acristavus is paleontologically significant because it supports the position that the ancestor of all hadrosaurids did not possess cranial ornamentation, and that ornamentation was an adaptation that later arose interdependently in the subfamilies Saurolophinae and Lambeosaurinae. It is closely related to Brachylophosaurus and Maiasaura, and was assigned to a new clade called Brachylophosaurini.

Aralosaurini

Aralosaurini is a tribe of basal lambeosaurine hadrosaurs endemic to Eurasia. It currently contains Aralosaurus (from the Aral sea of Kazakhstan) and Canardia (from Toulouse, Southern France).

Barsboldia

Barsboldia (meaning "of Barsbold", a well-known Mongolian paleontologist) was a genus of large hadrosaurid dinosaur from the early Maastrichtian Nemegt Formation of Ömnogöv', Mongolia. It is known from a partial vertebral column, partial pelvis, and some ribs.

Bonapartesaurus

Bonapartesaurus is an extinct genus of herbivorous ornithopod dinosaur belonging to Hadrosauridae, which lived in the area of the modern Argentina during the Campanian and Maastrichtian stages of the Late Cretaceous.

Brachylophosaurini

Brachylophosaurini is a tribe of saurolophine hadrosaurs with known material being from N. America and potentially Asia. It contains at least four taxa; Acristavus (from Montana and Utah), Brachylophosaurus (from Montana and Alberta), Maiasaura (also from Montana), and Probrachylophosaurus (also from Montana). A hadrosaur from the Amur river, Wulagasaurus, might be a member of this tribe, but this is disputed. The group was defined by Terry A. Gates and colleagues in 2011.The clade Brachylophosaurini was defined as "Hadrosaurine ornithopods more closely related to Brachylophosaurus, Maiasaura, or Acristavus than to Gryposaurus or Saurolophus".

Charles Mortram Sternberg

Charles Mortram Sternberg (1885–1981) was an American-Canadian fossil collector and paleontologist, son of Charles Hazelius Sternberg.

Late in his career, he collected and described Pachyrhinosaurus, Brachylophosaurus, Parksosaurus and Edmontonia. A contemporary author wrote, "No published study of Canadian dinosaurs is possible today without citing one or another of Sternberg's papers."

Corythosaurus

Corythosaurus is a genus of hadrosaurid "duck-billed" dinosaur from the Upper Cretaceous Period, about 77–75.7 million years ago. It lived in what is now North America. Its name means "helmet lizard", derived from Greek κόρυς. It was named and described in 1914 by Barnum Brown. Corythosaurus is now thought to be a lambeosaurine, related to Nipponosaurus, Velafrons, Hypacrosaurus, and Olorotitan. Corythosaurus has an estimated length of 9 metres (30 ft), and has a skull, including the crest, that is 70.8 centimetres (27.9 in) tall.

Corythosaurus is known from many complete specimens, including the nearly complete holotype found by Brown in 1911. The holotype skeleton is only missing the last section of the tail, and part of the forelimbs, but was preserved with impressions of polygonal scales. Corythosaurus is known from many skulls with tall crests. The crests resemble the crests of the cassowary and a Corinthian helmet. The most likely function of the crest is thought to be vocalization. As in a trombone, sound waves would travel through many chambers in the crest, and then get amplified when Corythosaurus exhaled. A Corythosaurus specimen has been preserved with its last meal in its chest cavity. Inside the cavity were remains of conifer needles, seeds, twigs, and fruits: Corythosaurus probably fed on all of these.

The two species of Corythosaurus are both present in slightly different levels of the Dinosaur Park Formation. Both still co-existed with theropods and other ornithischians, like Daspletosaurus, Brachylophosaurus, Parasaurolophus, Scolosaurus, and Chasmosaurus.

Gilmoreosaurus

Gilmoreosaurus is the name given to a genus of dinosaur from the Cretaceous of Asia. The type species is Gilmoreosaurus mongoliensis. It is believed to be a hadrosaur or iguanodont from the Iren Dabasu Formation of Mongolia, dating to 70 Ma ago. Additional specimens have been described as distinct species, including G. atavus from the Khodzhakul Formation of Uzbekistan (120 Ma ago) and G. arkhangelskyi from the Bissekty Formation (89 Ma ago). However, these are based on very fragmentary remains, and their classification is dubious. An additional species, G. kysylkumensis (also from the Bissekty Formation) is sometimes included, though it has also been referred to the related genus Bactrosaurus.

The first Gilmoreosaurus fossil remains were collected by George Olsen in 1923 and consisted of disarticulated bones from several individuals at different localities. They were originally assigned to the genus Mandschurosaurus but later given the separate genus Gilmoreosaurus, which was characterized by its combination of basal iguanodontian and hadrosaurid traits. Although a consensus on the exact taxonomic placement of this genus remains unreached, a 2010 study by Prieto-Márquez and Norell places the animal in a closely related outgroup to Hadrosauridae, based on a reassessment of its taxonomic status using a large-sample phylogenic analysis.In 2003, evidence of tumors, including hemangiomas, desmoplastic fibroma, metastatic cancer, and osteoblastoma was discovered in fossilized Gilmoreosaurus skeletons. Rothschild et al. tested dinosaur vertebrae for tumors using computerized tomography and fluoroscope screening. Several other hadrosaurids, including Brachylophosaurus, Edmontosaurus, and Bactrosaurus, also tested positive. Although more than 10,000 fossils were examined in this manner, the tumors were limited to Gilmoreosaurus and closely related genera. The tumors may have been caused by environmental factors or genetic propensity.

Hadrosauridae

Hadrosaurids (Greek: ἁδρός, hadrós, "stout, thick"), 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 family, which includes ornithopods such as Edmontosaurus and Parasaurolophus, was a common group of herbivores during the Late Cretaceous Period in what is now Asia, Europe, Antarctica, South America, and North America. Hadrosaurids are descendants of the Upper Jurassic/Lower Cretaceous iguanodontian dinosaurs and had a similar body layout.

Like other ornithischians, hadrosaurids had a predentary bone and a pubic bone which was positioned backwards in the pelvis. Hadrosauridae is divided into two principal subfamilies: the lambeosaurines (Lambeosaurinae), which had hollow cranial crests or tubes; and the saurolophines (Saurolophinae), identified as hadrosaurines (Hadrosaurinae) in most pre-2010 works, which lacked hollow cranial crests (solid crests were present in some forms). Saurolophines tended to be bulkier than lambeosaurines. Lambeosaurines included the aralosaurins, tsintaosaurins, lambeosaurins and parasaurolophins, while saurolophines included the brachylophosaurins, kritosaurins, saurolophins and edmontosaurins.

Hadrosaurids were facultative bipeds, with the young of some species walking mostly on two legs and the adults walking mostly on four. Their jaws were evolved for grinding plants, with multiple rows of teeth replacing each other as the teeth wore down.

Judith River Formation

The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the Late Cretaceous, between 80 and 75 million years ago, corresponding to the "Judithian" land vertebrate age. It was laid down during the same time period as portions of the Two Medicine Formation of Montana and the Oldman Formation of Alberta.

It is an historically important formation, explored by early American paleontologists such as Edward Drinker Cope, who named several dinosaurs from scrappy remains found here on his 1876 expedition (such as Monoclonius). Modern work has found nearly complete skeletons of the hadrosaurid Brachylophosaurus.

Maiasaura

Maiasaura (from the Greek "μαία" and the feminine form of Latin saurus, meaning "good mother reptile" or "good mother lizard" ) is a large herbivorous hadrosaurid ("duck-billed") dinosaur genus that lived in the area currently covered by the state of Montana in the Upper Cretaceous Period (mid to late Campanian), about 76.7 million years ago.The first fossils of Maiasaura were discovered in 1978. The genus was named in 1979. The name refers to the find of nests with eggs, embryos and young animals, in a nesting colony. These showed that Maiasaura fed its young while they were in the nest, the first time such evidence was obtained for a dinosaur. Hundreds of bones of Maiasaura have been dug up.

Maiasaura was about 9 metres (30 ft) long. Young animals walked on their hind legs, adults on all fours. Maiasaura was probably closely related to Brachylophosaurus.

Malta, Montana

Malta ( (listen) MAL-tə) is a city in, and the county seat of, Phillips County, Montana, United States, located at the intersection of U.S. Routes 2 and 191. The population was 1,997 at the 2010 census.

Oldman Formation

The Oldman Formation is a stratigraphic unit of Late Cretaceous (Campanian stage) age that underlies much of southern Alberta, Canada. It consists primarily of sandstones that were deposited in fluvial channel and floodplain environments. It was named for exposures along the Oldman River between its confluence with the St. Mary River and the city of Lethbridge, and it is known primarily for its dinosaur remains and other fossils.

Probrachylophosaurus

Probrachylophosaurus bergei is a species of large herbivorous brachylophosaurin hadrosaurid dinosaur known from the Late Cretaceous Campanian Judith River Formation, of Montana.

The significance of this particular hadrosaur taxon is that it is a transitional species between the genera Acristavus and Brachylophosaurus evolving from a crestless ancestor (the former genus) to its crested descendant (the latter genus) while changing the morphology of its nasal bones.

Prosaurolophus

Prosaurolophus (; meaning "before Saurolophus", in comparison to the later dinosaur with a similar head crest) is a genus of hadrosaurid (or duck-billed) 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 (30 ft), 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.

Saurolophinae

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 Hadrosaurinae is based on the genus Hadrosaurus which was found in more recent studies to be more primitive than either lambeosaurines or other traditional "hadrosaurines", like Edmontosaurus and Saurolophus. As a result of this, the name Hadrosaurinae was dropped or restricted to Hadrosaurus alone, and the subfamily comprising the traditional "hadrosaurines" was renamed the Saurolophinae. Recent phylogenetic work by Hai Xing indicates that Hadrosaurus is placed within the monophyletic group containing all non-lambeosaurine hadrosaurids. Under this view, the traditional Hadrosaurinae is resurrected, with the Hadrosauridae being divided into two clades: Hadrosaurinae and Lambeosaurinae.

Saurolophinae was first defined as a clade in a 2010 phylogenetic analysis by Prieto-Márquez. Traditionally, the "crestless" branch of the family Hadrosauridae had been named Hadrosaurinae. However, the use of the term Hadrosaurinae was questioned in a comprehensive study of hadrosaurid relationships by Albert Prieto-Márquez in 2010. Prieto-Márquez noted that, though the name Hadrosaurinae had been used for the clade of mostly crestless hadrosaurids by nearly all previous studies, its type species, Hadrosaurus foulkii, has almost always been excluded from the clade that bears its name, in violation of the rules for naming animals set out by the ICZN. Prieto-Márquez (2010) defined Hadrosaurinae as only the lineage containing H. foulkii, and used the name Saurolophinae instead for the traditional grouping.The cladogram below follows Godefroit et al. (2012) analysis.

The following cladogram was recovered in the 2013 phylogenetic analysis by Prieto-Márquez (the relationships within Lambeosaurinae and between basal hadrosauroids aren't shown).

Shantungosaurus

Shantungosaurus, meaning "Shandong Lizard", is a genus of saurolophine hadrosaurid dinosaurs found in the Late Cretaceous Wangshi Group of the Shandong Peninsula in China. The stratigraphic interval of Shantungosaurus ranges from the top of the Xingezhuang Formation to the middle of the Hongtuya Formation, middle to late Campanian in age. Shantungosaurus is so far the largest hadrosauroid taxon in the world: the greatest length of its femur is about 1.7 m, and the greatest length of its humerus is about 0.97 m.

Wulagasaurus

Wulagasaurus (meaning "Wulaga lizard", in reference to the discovery locality) is a genus of saurolophine hadrosaurid dinosaur from the Late Cretaceous of Heilongjiang, China. Its remains were found in a bonebed in the middle Maastrichtian-age Yuliangze Formation, dated to 69 million years ago. This bonebed is otherwise dominated by fossils of the lambeosaurine hadrosaurid (hollow-crested duckbill) Sahaliyania. Wulagasaurus was named by Pascal Godefroit and colleagues in 2008. Only partial remains are known at this time. It is one of several hadrosaurids from the Amur River region named since 2000. The type and only species to date is W. dongi, named in honor of Chinese paleontologist Dong Zhiming.

Wulagasaurus is based on GMH W184, a partial dentary (toothbearing bone of the lower jaw). Godefroit and colleagues assigned additional remains from the bonebed to their new genus, including three braincases, a cheekbone, two maxillae (the toothbearing bone of the upper jaw), another dentary, two shoulder blades, two sternal elements, two upper arm bones, and an ischium. It can be distinguished from other hadrosaurids by its slender dentary and the unique form of its upper arm, which had distinctive articulations and placements for muscle attachments. Godefroit and colleagues performed a phylogenetic analysis that suggests Wulagasaurus was the most basal saurolophine known (which would result in a long ghost lineage), and interpreted this as evidence that saurolophines and hadrosaurids in general originated in Asia, which has been supported by other finds since. As a hadrosaurid, Wulagasaurus would have been an herbivore.In recent studies conducted by researchers from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), along with others from Chinese Academy of Science, American Museum of Natural History, and Geological Museum of Heilongjiang Provinces, re-evaluated and re-described Wulagasaurus dongi. Based on both original and recent specimens, they concluded that Wulagasaurus shared many morphological similarities with North American taxon's Brachylophosaurus and Maiasaura, possibly forming a clade-structure within the already existing clade Brachylophosaurini. This hypothesis has been demonstrated by another phylogenetic analysis recently coming out.

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