Saurolophus is a
genusIn biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of large
hadrosaurineSaurolophinae is a subfamily of hadrosaurid dinosaurs. Members of the subfamily derive from the Late Cretaceous of Antarctica, Argentina, Canada , China, Kazakhstan, Mexico, Russia, the United States and...
duckbillHadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...
that lived about 69.5-68.5 million years ago, in the
Late CretaceousThe Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
of
North AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and
AsiaAsia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
; it is one of the few genera of
dinosaurDinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s known from multiple continents. It is distinguished by a spike-like crest which projects up and back from the skull.
Saurolophus was a herbivorous dinosaur which could move about either
bipedBipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...
ally or
quadrupedQuadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
ally.
The
type speciesIn biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
,
S. osborni, was described by
Barnum BrownBarnum Brown , a paleontologist born in Carbondale, Kansas, and named after the circus showman P.T. Barnum, discovered the second fossil of Tyrannosaurus rex during a career that made him one of the most famous fossil hunters working from the late Victorian era into the early 20th century.Sponsored...
in 1912 from
CanadianCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
fossils. A second valid species,
S. angustirostris, is represented by numerous specimens from Mongolia, and was described by
Anatoly Konstantinovich RozhdestvenskyAnatoly Konstantinovich Rozhdestvensky was a Russian paleontologist responsible for naming many dinosaurs, including Aralosaurus and Probactrosaurus....
. A third species,
S. "morrisi" from
CaliforniaCalifornia is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, is in press at this time, and a fourth species,
S. kryschtofovici from
ChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, is considered
dubiousIn zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
.
Description
Saurolophus is known from material including nearly complete skeletons, giving researchers a clear picture of its bony anatomy.
S. osborni, the rarer
AlbertaAlberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
n species, was around 9.8 meters long (32 feet), with its skull a meter long (3.3 feet). It weight is estimated at 1.9
tonneThe tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
s (2.1 tons).
S. angustirostris, the
MongoliaMongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
n species, was larger; the
typeA holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
skeleton is roughly 12 meters long (39.4 ft), and larger remains are reported. Aside from size, the two species are virtually identical, with differentiation hindered by lack of study.
The most distinctive feature of
Saurolophus is its cranial crest, which is present in young individuals but is smaller. It is long and spike-like and projects upward and backward at about a 45 degree angle, starting from over the eyes. This crest is often described as solid, but appears to be solid only at the point, with internal chambers that may have had a
respiratory'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
and/or heat-regulation function.
Classification
Barnum BrownBarnum Brown , a paleontologist born in Carbondale, Kansas, and named after the circus showman P.T. Barnum, discovered the second fossil of Tyrannosaurus rex during a career that made him one of the most famous fossil hunters working from the late Victorian era into the early 20th century.Sponsored...
, who described the first specimens, put it in its own subfamily in "Trachodontidae" (=Hadrosauridae), the Saurolophinae. At the time, this also included
CorythosaurusCorythosaurus is a genus of duck-billed dinosaur from the Upper Cretaceous Period, about 77-76.5 million years ago. It lived in what is now North America...
and
HypacrosaurusHypacrosaurus was a genus of duckbill dinosaur similar in appearance to Corythosaurus. Like Corythosaurus, it had a tall, hollow rounded crest, although not as large and straight...
, the only well-known examples of what would become
LambeosaurinaeLambeosaurinae is a group of crested hadrosaurid dinosaurs.-Classification:Lambeosaurines have been split into Parasaurolophini and Corythosaurini . Corythosaurini and Parasaurolophini as terms entered the formal literature in Evans and Reisz's 2007 redescription of Lambeosaurus magnicristatus...
. Brown thought that
Saurolophus had an expanded tip to the ischium bone in the hip, as dinosaurs now recognized as lambeosaurines had, but this appears to have been based on a mistakenly associated lambeosaurine ischium. Additionally, he misinterpreted the crests of
Saurolophus and lambeosaurines as being made of the same bones.
Most publications before 2010 classified
Saurolophus as a member of Hadrosaurinae, often known colloquially as the "flat-headed hadrosaurs". In 2010, the subfamily Saurolophinae was brought back into use because
HadrosaurusHadrosaurus is a valid genus of hadrosaurid dinosaur. In 1858, a skeleton of a dinosaur from this genus was the first dinosaur skeleton known from more than isolated teeth to be found in North America. In 1868, it became the first ever mounted dinosaur skeleton...
appears to have branched off prior to the "hadrosaurine"–lambeosaurine split. As a result, Hadrosaurinae by definition cannot include the traditional "hadrosaurines". Saurolophinae is the oldest available name for the former "hadrosaurine"
cladeA clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
.
Saurolophus, as the name suggests, is a saurolophine, as it has a saurolophine
pelvisIn human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
and a (largely) solid crest.
Discovery and history
Barnum Brown recovered the first described remains of
Saurolophus in 1911, including a nearly complete skeleton (
AMNH 5220The American Museum of Natural History , located on the Upper West Side of Manhattan in New York City, United States, is one of the largest and most celebrated museums in the world...
). Now on display in the American Museum of Natural History, this skeleton was the first nearly complete dinosaur skeleton from Canada. It was found in rocks of
early MaastrichtianThe Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
age, in the Upper Cretaceous
Horseshoe Canyon FormationThe Horseshoe Canyon Formation is part of the Edmonton Group and is up to 230m in thickness. It is Late Campanian to Early Maastrichtian in age and is composed of mudstone, sandstone, and carbonaceous shales...
(then known as the Edmonton Formation) near Tolman Ferry on the
Red Deer RiverThe Red Deer River is a river in Alberta, Canada. It is a major tributary of the South Saskatchewan River.Red Deer River has a total length of and a drainage area of...
in Alberta. Brown wasted little time in describing his material, giving it its own subfamily.
Saurolophus was an important early reference for other hadrosaurs, as seen in the names of
Prosaurolophus ("before
Saurolophus") and
ParasaurolophusParasaurolophus is a genus of ornithopod dinosaur that lived in what is now North America during the Late Cretaceous Period, about 76.5–73 million years ago. It was an herbivore that walked both as a biped and a quadruped. Three species are recognized: P. walkeri , P. tubicen, and the...
("near
Saurolophus"). However, little additional material has been recovered and described.
Instead, more abundant remains from
AsiaAsia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
have provided more data. Initial remains were not promising: a partial fragmentary ischium from
HeilongjiangFor the river known in Mandarin as Heilong Jiang, see Amur River' is a province of the People's Republic of China located in the northeastern part of the country. "Heilongjiang" literally means Black Dragon River, which is the Chinese name for the Amur. The one-character abbreviation is 黑...
,
ChinaChina , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
that Riabinin named
S. kryschtofovici. Much better remains were soon recovered, though, but from
MongoliaMongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
's early Maastrichtian-age
Nemegt FormationThe Nemegt Formation is a geological formation dating from the Late Cretaceous sedimentary from the Gobi Desert of Mongolia. It overlies and sometimes forms folds with the Barun Goyot Formation. It consists of river channel sediments and contains fossils of fish, turtles, crocodilians, birds and a...
. The 1947-49
Polishthumb|right|180px|The state flag of [[Poland]] as used by Polish government and diplomatic authoritiesThe Polish people, or Poles , are a nation indigenous to Poland. They are united by the Polish language, which belongs to the historical Lechitic subgroup of West Slavic languages of Central Europe...
-
MongolianMongols ) are a Central-East Asian ethnic group that lives mainly in the countries of Mongolia, China, and Russia. In China, ethnic Mongols can be found mainly in the central north region of China such as Inner Mongolia...
Paleontological Expedition recovered the large skeleton that became
S. angustirostris as described by
Anatoly RozhdestvenskyAnatoly Konstantinovich Rozhdestvensky was a Russian paleontologist responsible for naming many dinosaurs, including Aralosaurus and Probactrosaurus....
. Other skeletons from a variety of growth stages have also been discovered, and
S. angustirostris is now the most abundant Asian hadrosaurid.
In 1973, three partial skeletons were found in the
Moreno FormationThe Moreno Formation is a Mesozoic geologic formation. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation.-Dinosaurs:-Mosasaurs:-Plesiosaurs:-Turtles:-See also:...
of
CaliforniaCalifornia is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. These specimens were referred to cf.
Saurolophus sp. In 2010, one of the skulls was instead assigned to
EdmontosaurusEdmontosaurus is a genus of crestless hadrosaurid dinosaur. It contains two species: Edmontosaurus regalis and Edmontosaurus annectens. Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian stage of the Cretaceous Period 73 million years ago,...
. A newer study placed the three specimens in a new species,
S. "morrisi". Because the study has not yet been published,
S. "morrisi" is currently a
nomen nudumThe phrase nomen nudum is a Latin term, meaning "naked name", used in taxonomy...
.
Species
Two species are regarded as valid today: the
type speciesIn biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
S. osborni, and
S. angustirostris.
S. osborni (Brown, 1912) is known from a skull and skeleton, two other complete skulls, and skull fragments.
S. angustirostris (Rozhdestvensky, 1952) is known from at least fifteen specimens. It differs from
S. osborni by some details of the skull. For example, the Mongolian species had a longer skull (by 20%) and the front of the snout (the
premaxillaThe incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
ry bones) were more upwardly-directed.
S, kryschtofovici (Riabinin, 1930) is not considered valid; either it is regarded as a
dubiousIn zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
name, or as a synonym of
S. angustirostris (although the name predates
S. angustirostris). As noted above,
S. "morrisi" is in press and is not yet official.
Paleoecology
S. osborni shared the Horseshoe Canyon Formation with fellow hadrosaurids
Edmontosaurus and hollow-crested
Hypacrosaurus,
hypsilophodontHypsilophodonts were small ornithopod dinosaurs, regarded as fast, herbivorous bipeds on the order of 1–2 meters long . They are known from Asia, Australia, Europe, New Zealand, North America, and South America, from rocks of Middle Jurassic to late Cretaceous age...
ParksosaurusParksosaurus was a genus of hypsilophodont ornithopod dinosaur from the early Maastrichtian-age Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. It is based on most of a partially articulated skeleton and partial skull, showing it to have been a small, bipedal, herbivorous dinosaur...
,
ankylosauridAn ankylosaurid is a member of the Ankylosauridae family of armored dinosaurs that evolved 125 million years ago and became extinct 65 million years ago during the Cretaceous-Tertiary extinction event...
EuoplocephalusEuoplocephalus was one of the largest genera of ankylosaurian dinosaurs, at about the size of a small elephant. It is also the ankylosaurian with the best fossil record, so its extensive spiked armor, low-slung body and great club-like tail are well documented.-Description:Among the...
,
nodosauridNodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous Period of what are now North America, Asia, Antarctica and Europe.-Characteristics:...
EdmontoniaEdmontonia was an armoured dinosaur, a part of the nodosaur family from the Late Cretaceous Period. It is named after the Edmonton Formation , the unit of rock it was found in.-Description:...
, horned dinosaurs
MontanoceratopsMontanoceratops was a genus of small ceratopsian dinosaur. It lived during the early Maastrichtian of the late Cretaceous Period...
,
AnchiceratopsAnchiceratops is a genus of chasmosaurine ceratopsid dinosaur from the Late Cretaceous Period of western North America. Like other ceratopsids, it was a quadrupedal herbivore with three horns on its face, a parrot-like beak, and a long frill extending from the back of its head. The two horns above...
,
ArrhinoceratopsArrhinoceratops is a genus of ceratopsian dinosaur. The name was coined as its original describer concluded it had no nose-horn, however further analysis revealed this not to be the case...
, and
PachyrhinosaurusPachyrhinosaurus is a genus of ceratopsid dinosaurs from the Late Cretaceous period of North America. The first examples were discovered by Charles M. Sternberg in Alberta, Canada, in 1946, and named in 1950. Over a dozen partial skulls and a large assortment of other fossils from various species...
, pachycephalosaurid
StegocerasStegoceras is a genus of plant-eating pachycephalosaurid dinosaur that lived in what is now North America during the Late Cretaceous period....
,
ostrich-mimicsThe Ornithomimosauria, ornithomimosaurs or ostrich dinosaurs were theropod dinosaurs which bore a superficial resemblance to modern ostriches. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia...
OrnithomimusOrnithomimus is a genus of ornithomimid dinosaur from the Late Cretaceous Period of what is now North America.In 1890 Ornithomimus velox was named by Othniel Charles Marsh on the basis of a foot and partial hand from the Maastrichtian Denver Formation. Another seventeen species have been named since...
and
StruthiomimusStruthiomimus is a genus of ornithomimid dinosaur from the late Cretaceous of Alberta, Canada. It was a long-legged, ostrich-like dinosaur.The bipedal Struthiomimus stood about long and tall at the hips and weighed around...
, a variety of poorly-known small theropods including
troodontidsTroodontidae is a family of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and scrappy and they have therefore been allied, at various times, with many dinosaurian lineages...
and
dromaeosauridsDromaeosauridae is a family of bird-like theropod dinosaurs. They were small- to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek dromeus meaning 'runner' and sauros meaning 'lizard'...
, and the
tyrannosaursTyrannosauridae is a family of coelurosaurian theropod dinosaurs which comprises two subfamilies containing up to six genera, including the eponymous Tyrannosaurus. The exact number of genera is controversial, with some experts recognizing as few as three...
AlbertosaurusAlbertosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, more than 70 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which...
and
DaspletosaurusDaspletosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America between 77 and 74 million years ago, during the Late Cretaceous Period. Fossils of the only named species were found in Alberta, although other possible species from Alberta and Montana await...
. The dinosaurs from this formation are sometimes known as Edmontonian, after a
land mammal ageFaunal Assemblage is the archaeological or paleontological term for a group of associated animal fossils found together in a given stratum.The principle of faunal succession is used in biostratigraphy to determine each biostratigraphic unit, or biozone...
, and are distinct from those in the formations above and below. The Horseshoe Canyon Formation is interpreted as having a significant
marineAn ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
influence, due to an encroaching
Western Interior SeawayThe Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves, Laramidia and Appalachia, during most of the mid- and late-Cretaceous Period...
, the
shallow seaAn epeiric sea is a shallow sea that extends over part of a continent.Epeiric seas are usually associated with the marine transgressions of the geologic past, which have variously been due to either global eustatic sea level changes, local tectonic deformation, or both, and are occasionally...
that covered the midsection of North America through much of the
CretaceousThe Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
.
S. osborni may have preferred to stay more landward.
S. angustirostris was one of the largest herbivores of the Nemegt Formation, which lacked large horned dinosaurs but had sauropods and a more diverse theropod fauna. It coexisted with the rare crested hadrosaurid
BarsboldiaBarsboldia 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...
, flat-headed pachycephalosaurian
HomalocephaleHomalocephale is a genus of dinosaur belonging to the pachycephalosaurid family, which lived during the late Cretaceous period of what is now Mongolia, 80 million years ago. The genus was described in 1974 by Osmólska & Maryañska, and consists of a single species, H...
and domed
PrenocephalePrenocephale was a small pachycephalosaurid dinosaur genus from the Late Cretaceous and was similar in many ways to its close relative, Homalocephale, which may simply represent Prenocephale juveniles. Adult Prenocephale probably weighed around and measured around long...
, the large ankylosaurid
TarchiaTarchia is a genus of ankylosaurid dinosaur from the late Cretaceous of Mongolia. It is currently the geologically youngest known of all the Asian ankylosaurid dinosaurs and is represented by five or more specimens, including two complete skulls and one nearly complete postcranial skeleton...
, rare
saltasauridSaltasauridae is a family of titanosaurian dinosaurs known from the late Cretaceous period of South America, Spain, Madagascar and Mongolia....
sauropods
NemegtosaurusNemegtosaurus was a sauropod dinosaur from Late Cretaceous Period of what is now Mongolia. It was named after the Nemegt Basin in the Gobi Desert, where the remains — a single skull — were found...
and
OpisthocoelicaudiaOpisthocoelicaudia was 12-metre-long sauropod dinosaur of the Late Cretaceous Period discovered in Mongolia in 1965 by Polish and Mongolian scientists in what is now the Gobi Desert...
, the
alvarezsauridAlvarezsauridae is an enigmatic family of small, long-legged running dinosaurs. Although originally thought to represent the earliest known flightless birds, a consensus of recent work suggests that they are primitive members of the Maniraptora. Other work found them to be the sister group to the...
MononykusMononykus was a theropod dinosaur from late Cretaceous Mongolia with long, skinny legs. It moved about on two legs, was very nimble, and could run at high speeds, something that would have been useful in the open desert plains where it lived...
, three types of troodontids including
SaurornithoidesSaurornithoides is a genus of troodontid maniraptoran dinosaur, living during the Late Cretaceous period. These creatures were predators, which could run fast on their hind legs and had excellent sight and hearing...
, several
oviraptorosauriaOviraptorosaurs are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot - like skulls, with or without bony crests atop the head...
ns including
RincheniaRinchenia is a genus of Mongolian oviraptorid dinosaur from the late Cretaceous Period. The type species, Rinchenia mongoliensis, was originally classified as a species within the genus Oviraptor , but a re-examination by Barsbold in 1997 found differences significant enough to warrant a separate...
and
NomingiaNomingia is a genus of oviraptorid theropod dinosaur hailing from the Late Cretaceous Bugin Tsav Beds of Mongolia.-Discovery and naming:...
, the ostrich-mimics
GallimimusGallimimus is a genus of ornithomimid theropod dinosaur from the late Cretaceous period Nemegt Formation of Mongolia. With individuals as long as , it was one of the largest ornithomimosaurs...
and
DeinocheirusDeinocheirus is a genus of large theropod dinosaur, possibly an ornithomimosaurian, which lived in what is now southern Mongolia, during the late Cretaceous Period .-Discovery and naming:...
,
therizinosaurTherizinosaurs are theropod dinosaurs belonging to the clade Therizinosauria. Therizinosaur fossils have been found in Early through Late Cretaceous deposits in Mongolia, the People's Republic of China and Western North America...
id
TherizinosaurusTherizinosaurus is a genus of very large theropod dinosaur. Therizinosaurus lived in the late Cretaceous Period , and was one of the last and largest representatives of its unique group, the Therizinosauria...
, tyrannosaurid relative
BagaraatanBagaraatan was a genus of theropod dinosaur from the Late Cretaceous period. Its fossils were found in the Nemegt Formation of Mongolia. Bagaraatan may have been around 3–4 metres in length....
, and the tyrannosaurid
TarbosaurusTarbosaurus is a genus of tyrannosaurid theropod dinosaur that flourished in Asia about 70 million years ago, at the end of the Late Cretaceous Period. Fossils have been recovered in Mongolia, with more fragmentary remains found further afield in parts of China. Although many species have been...
. Unlike other Mongolian formations like the well-known
Djadochta FormationThe Djadochta Formation is situated in central Asia and dates from the Late Cretaceous Period. Laid down in the early Campanian, possibly starting in the latest Santonian, it is dated somewhat uncertainly at about 84-75 mya...
that includes
VelociraptorVelociraptor is a genus of dromaeosaurid theropod dinosaur that existed approximately 75 to 71 million years ago during the later part of the Cretaceous Period. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis; fossils...
and
ProtoceratopsProtoceratops is a genus of sheep-sized herbivorous ceratopsian dinosaur, from the Upper Cretaceous Period of what is now Mongolia. It was a member of the Protoceratopsidae, a group of early horned dinosaurs...
, the Nemegt is interpreted as being well-watered, like the
Dinosaur Park FormationThe Dinosaur Park Formation is the uppermost member of the Judith River Group, a major geologic unit in southern Alberta. It was laid down over a period of time between about 76.5 and 75 million years ago. The formation is made up of deposits of a high-sinuosity fluvial system, and is capped...
in Alberta.
Paleobiology
As a
hadrosauridHadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...
,
Saurolophus would have been a bipedal/
quadrupedQuadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al
herbivoreHerbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
, eating a variety of
plantPlants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s. Its skull permitted a grinding motion analogous to
chewingMastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion and it increases the surface area of foods to allow more efficient break down by enzymes. During the mastication process, the food is positioned between the teeth for grinding by...
, and its
teethTeeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
were continually replacing and packed into dental batteries 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
cheekCheeks constitute the area of the face below the eyes and between the nose and the left or right ear. They may also be referred to as jowls. "Buccal" means relating to the cheek. In humans, the region is innervated by the buccal nerve...
-like organ. Its feeding range would have extended from the ground to ~4 meter (13 ft) above. Common
S. angustirostris would have been an important large herbivore in the
Nemegt FormationThe Nemegt Formation is a geological formation dating from the Late Cretaceous sedimentary from the Gobi Desert of Mongolia. It overlies and sometimes forms folds with the Barun Goyot Formation. It consists of river channel sediments and contains fossils of fish, turtles, crocodilians, birds and a...
, but
S. osborni was rare in the
Horseshoe Canyon FormationThe Horseshoe Canyon Formation is part of the Edmonton Group and is up to 230m in thickness. It is Late Campanian to Early Maastrichtian in age and is composed of mudstone, sandstone, and carbonaceous shales...
and faced competition from other duckbills (
EdmontosaurusEdmontosaurus is a genus of crestless hadrosaurid dinosaur. It contains two species: Edmontosaurus regalis and Edmontosaurus annectens. Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian stage of the Cretaceous Period 73 million years ago,...
and
HypacrosaurusHypacrosaurus was a genus of duckbill dinosaur similar in appearance to Corythosaurus. Like Corythosaurus, it had a tall, hollow rounded crest, although not as large and straight...
). Comparisons between the
scleral ringSclerotic rings are rings of bone found in the eyes of several groups of vertebrate animals, except for mammals and crocodilians. They can be made up of single bones or small bones together. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical,...
s of
Saurolophus and modern birds and reptiles suggest that it may have been
cathemeralA cathemeral organism is one that has sporadic and random intervals of activity during the day or night in which food is acquired, socializing with other organisms occurs, and any other activities necessary for livelihood are performed...
, active throughout the day at short intervals.
Crest
The distinctive spike-like crest of
Saurolophus has been interpreted in multiple ways, and could have had multiple functions. Brown compared it to the crest of a
chameleonChameleons are a distinctive and highly specialized clade of lizards. They are distinguished by their parrot-like zygodactylous feet, their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues, their swaying gait, the possession by many of a...
, and suggested it could provide an area for muscle attachment and a connection point for a nonbody back frill like that seen in the
basilisk lizardBasiliscus is a genus of large corytophanid lizards, commonly known as basilisks, which are endemic to southern Mexico, Central America, and northern South America.-Taxonomy and etymology:...
.
Peter DodsonPeter Dodson is an American paleontologist who has published many papers and written and collaborated on books about dinosaurs. An authority on Ceratopsians, he has also authored several papers and textbooks on hadrosaurs and sauropods, and is a co-editor of The Dinosauria, widely considered the...
interpreted similar features in other duckbills as having use in sexual identification. Maryańska and Osmólska, noting the hollow base, suggested that the crest increased the surface area of the respiratory cavity, and helped in thermoregulation.
James HopsonJames Allen Hopson is an American paleontologist and professor at the University of Chicago. His work has focused on the evolution of the synapsids , and has been focused on the transition from basal synapsids to mammals, from the late Paleozoic through the Mesozoic Eras...
supported a function as a visual signal, and further mentioned the possibility that there were inflatable skin flaps over the nostrils that could have acted as resonators and additional visual signals. This idea has been picked up by authors of popular dinosaur works, such as
David B. NormanDavid Bruce Norman is a British paleontologist, currently Director of the Sedgwick Museum, Cambridge University. He is a fellow at Christ's College, Cambridge where he teaches geology in the Natural Sciences tripos. He is a member of the Palaeontological Association. He has studied Iguanodon...
who discussed hadrosaurid display at length and included a life restoration of such an adaptation in action.
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