Parasaurolophus
Encyclopedia
Parasaurolophus 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 (the type species
), P. tubicen, and the short-crested P. cyrtocristatus. Remains are known from Alberta
(Canada
), and New Mexico
and Utah
(USA). The genus was first described in 1922 by William Parks from a skull
and partial skeleton in Alberta.
Parasaurolophus was a hadrosaurid
, part of a diverse family
of Cretaceous dinosaurs known for their range of bizarre head adornments. This genus is known for its large, elaborate cranial crest, which at its largest forms a long curved tube projecting upwards and back from the skull
. Charonosaurus
from China
, which may have been its closest relative, had a similar skull and potentially a similar crest. The crest has been much discussed by scientists; the consensus is that major functions included visual recognition of both species and sex, acoustic resonance, and thermoregulation
. It is one of the rarer hadrosaurids, known from only a handful of good specimens.
Like most dinosaurs, the skeleton of Parasaurolophus is incompletely known. The length of the type specimen of P. walkeri is estimated at 9.5 m (31.2 ft), and its weight is estimated at 2.5 tonnes (2.8 ST). Its skull is about 1.6 m (5.2 ft) long, including the crest, whereas the type skull of P. tubicen is over 2 m (6.6 ft) long, indicating a larger animal. Its single known forelimb was relatively short for a hadrosaurid, with a short but wide shoulder blade
. The thighbone
measures 103 cm (40.6 in) long in P. walkeri and is robust for its length when compared to other hadrosaurids. The upper arm
and pelvic
bones were also heavily built.
Like other hadrosaurids, it was able to walk on either two legs or four. It probably preferred to forage for food on four legs, but ran on two. The neural spines
of the vertebrae were tall, as was common in lambeosaurines; tallest over the hips, they increased the height of the back. Skin
impressions are known for P. walkeri, showing uniform tubercle-like scales but no larger structures.
The most noticeable feature was the cranial crest, which protruded from the rear of the head and was made up of the premaxilla
and nasal bone
s. The P. walkeri type specimen has a notch in the neural spines near where the crest would hit the back, but this may be a pathology
peculiar to this individual. William Parks, who named the genus, hypothesized that a ligament
ran from the crest to the notch to support the head. Although this idea seems unlikely, Parasaurolophus is sometimes restored with a skin flap from the crest to the neck. The crest was hollow, with distinct tubes leading from each nostril to the end of the crest before reversing direction and heading back down the crest and into the skull. The tubes were simplest in P. walkeri, and more complex in P. tubicen, where some tubes were blind and others met and separated. While P. walkeri and P. tubicen had long crests with only slight curvature, P. cyrtocristatus had a short crest with a more circular profile.
because of its superficially similar crest. However, it was soon reassessed as a member of the lambeosaurine subfamily of hadrosaurids—Saurolophus is an hadrosaurine. It is usually interpreted as a separate offshoot of the lambeosaurines, distinct from the helmet-crested Corythosaurus
, Hypacrosaurus
, and Lambeosaurus
. Its closest known relative appears to be Charonosaurus
, a lambeosaurine with a similar skull (but no complete crest yet) from the Amur region of northeastern China, and the two may form a clade
Parasaurolophini. P. cyrtocristatus, with its short, rounder crest, may be the most basal
of the three known Parasaurolophus species, or it may represent subadult
or female specimens of P. tubicen.
Meaning "near crested lizard", the name Parasaurolophus is derived from the Greek
para/παρα "beside" or "near", saurus/σαυρος "lizard" and lophos/λοφος "crest". It is based on
ROM
768, a skull and partial skeleton missing most of the tail and the hind legs below the knees, which was found by a field party from the University of Toronto
in 1920 near Sand Creek along the Red Deer River
in Alberta, Canada. These rocks are now known as the Campanian
-age Upper Cretaceous Dinosaur Park Formation
. William Parks named the specimen P. walkeri in honor of Sir Byron Edmund Walker
, Chairman of the Board of Trustees of the Royal Ontario Museum
. Parasaurolophus remains are rare in Alberta, with only one other partial skull from (probably) the Dinosaur Park Formation, and three Dinosaur Park specimens lacking skulls, possibly belonging to the genus. In some faunal lists, there is a mention of possible P. walkeri material in the Hell Creek Formation
of Montana
, a rock unit of late Maastrichtian
age. This occurrence is not noted by Sullivan and Williamson in their 1999 review of the genus, and has not been further elaborated upon elsewhere.
In 1921, Charles H. Sternberg
recovered a partial skull (PMU
.R1250) from what is now known as the slightly younger Kirtland Formation
in San Juan County
, New Mexico. This specimen was sent to Uppsala
, Sweden
, where Carl Wiman
described it as a second species, P. tubicen, in 1931. The specific epithet is derived from the Latin
tǔbǐcěn "trumpeter". A second, nearly complete P. tubicen skull (NMMNH
P-25100) was found in New Mexico in 1995. Using computed tomography
of this skull, Robert Sullivan and Thomas Williamson gave the genus a monograph
ic treatment in 1999, covering aspects of its anatomy and taxonomy, and the functions of its crest. Williamson later published an independent review of the remains, disagreeing with the taxonomic conclusions.
John Ostrom
described another good specimen (FMNH
P27393) from New Mexico as P. cyrtocristatus in 1961. It includes a partial skull with a short, rounded crest, and much of the postcrania
l skeleton except for the feet, neck, and parts of the tail. Its specific name is derived from the Latin
curtus "shortened" and cristatus "crested". The specimen was found in either the top of the Fruitland Formation
or, more likely, the base of the overlying Kirtland Formation. The range of this species was expanded in 1979, when David B. Weishampel and James A. Jensen
described a partial skull with a similar crest (BYU
2467) from the Campanian-age Kaiparowits Formation
of Garfield County
, Utah
. Since then, another skull has been found in Utah with the short/round P. cyrtocristatus crest morphology.
P. walkeri, from Alberta, is known from a single definitive specimen from the Dinosaur Park Formation
, though others from the Dinosaur Park probably belong to it. It differs from P. tubicen by having simpler tubes in its crest, and from P. cyrtocristatus by having a long, unrounded crest and a longer upper arm
than forearm
. It lived between 76.5 and 75.3 million years ago.
P. tubicen, from New Mexico, is known from the remains of at least three individuals. It is the largest species, with more complex air passages in its crest than P. walkeri, and a longer, straighter crest than P. cyrtocristatus. P. tubicen is known only from the De-na-zin Member of the Kirtland Formation
, and lived about 73.4–73 million years ago, making it the most recent species.
P. cyrtocristatus, from the Kaiparowits
and Fruitland Formation
s of New Mexico and Utah, is known from three possible specimens. It lived 75.5–74.5 million years ago, and is the smallest species, with a short rounded crest. Its small size and the form of its crest have led several scientists to suggest that it represents juveniles or females of P. tubicen, though P. tubicen lived at least one million years later. As noted by Thomas Williamson, the type material of P. cyrtocristatus is about 72% the size of P. tubicen, close to the size at which other lambeosaurines are interpreted to begin showing definitive sexual dimorphism
in their crests (~70% of adult size). However, this position has been rejected in recent reviews of lambeosaurines.
Parasaurolophus walkeri, from the Dinosaur Park Formation
, was a member of a diverse and well-documented fauna
of prehistoric animals, including well-known dinosaurs such as the horned
Centrosaurus
and Chasmosaurus
; fellow duckbills Gryposaurus
and Corythosaurus; tyrannosaurid Gorgosaurus
; and armored
Edmontonia
, Euoplocephalus
and Dyoplosaurus
. It was a rare constituent of this fauna. The Dinosaur Park Formation is interpreted as a low-relief setting of river
s and floodplain
s that became more swamp
y and influenced by marine
conditions over time as the Western Interior Seaway
transgressed
westward. The climate
was warmer than present-day Alberta, without frost
, but with wetter and drier seasons. Conifers were apparently the dominant canopy plants, with an understory
of fern
s, tree ferns, and angiosperms.
Some of the less common hadrosaurs in the Dinosaur Park Formation of Dinosaur Provincial Park, such as Parasaurolophus, may represent the remains of individuals who died while migrating through the region. They might also have had a more upland habitat where they may have nested or fed. The presence of Parasaurolophus and Kritosaurus in northern latitude fossil sites may represent faunal exchange between otherwise distinct northern and southern biomes in Late Cretaceous North America. Both taxa are uncommon outside of the southern biome, where, along with Pentaceratops
, they are predominate members of the fauna.
In New Mexico and Utah, the species P. cyrtocristatus shared its environment with the horned ceratopsians Utahceratops
, Kosmoceratops
, and Pentaceratops
, and the coelurosaur Ornithomimus
, and the tyrannosaur Teratophoneus
.
The last and largest of the Parasaurolophus species, P. tubicen, lived in New Mexico alongside the large sauropod Alamosaurus
, duckbill Kritosaurus
, horned Pentaceratops, armored Nodocephalosaurus
, Saurornitholestes
, and the tyrannosaurid Bistahieversor
. The Kirtland Formation is interpreted as river floodplains appearing after a retreat of the Western Interior Seaway. Conifers were the dominant plants, and chasmosaurine
horned dinosaurs were apparently more common than hadrosaurids.
s with a sophisticated skull that permitted a grinding motion analogous to chewing
. Its teeth
were continually being replaced; they were packed into dental batteries containing hundreds of teeth, only a relative handful of which were in use at any time. It used its beak to crop plant material, which was held in the jaws by a cheek
-like organ. Vegetation could have been taken from the ground up to a height of around 4 meters (13 ft). As noted by Bob Bakker
, lambeosaurines have narrower beaks than hadrosaurines, implying that Parasaurolophus and its relatives could feed more selectively than their broad-beaked, crestless counterparts.
As for other lambeosaurines, it is believed that the cranial crest of Parasaurolophus changed with age and was a sexually dimorphic
characteristic in adults. James Hopson
, one of the first researchers to describe lambeosaurine crests in terms of such distinctions, suggested that P. cyrtocristatus, with its small crest, was the female form of P. tubicen. Thomas Williamson suggested it was the juvenile
form. Neither hypothesis became widely accepted. As only six good skulls and one juvenile braincase are known, additional material will help clear up these potential relationships. Williamson noted that in any case, juvenile Parasaurolophus probably had small, rounded crests like P. cyrtocristatus, that probably grew faster as individuals approached sexual maturity
. Recent restudy of a juvenile braincase previously assigned to Lambeosaurus, now assigned to Parasaurolophus, provides evidence that a small tubular crest was present in juveniles. This specimen preserves a small upward flaring of the frontal bone
s that was similar to but smaller than what is seen in adult specimens; in adults, the frontals formed a platform that supported the base of the crest. This specimen also indicates that the growth of the crest in Parasaurolophus and the facial profile of juvenile individuals differed from the Corythosaurus-Hypacrosaurus-Lambeosaurus model, in part because the crest of Parasaurolophus lacks the thin bony 'coxcomb' that makes up the upper portion of the crest of the other three lambeosaurines.
used as a breathing tube or for food gathering, Charles M. Sternberg
that it served as an airtrap to keep water out of the lung
s, and Ned Colbert
that it served as an air reservoir for prolonged stays underwater.
Other proposals were more physical in nature. As mentioned above, William Parks suggested that it was joined to the vertebrae with ligament
s or muscles, and helped with moving and supporting the head. Othenio Abel proposed it was used as a weapon in combat among members of the same species, and Andrew Milner suggested that it could be used as a foliage deflector, like the helmet crest (called a 'casque') of the cassowary
. Still other proposals made housing specialized organs the major function. Halszka Osmólska
suggested that it housed salt gland
s, and John Ostrom suggested that it housed expanded areas for olfactory tissue
and much improved sense of smell
of the lambeosaurines, which had no obvious defensive capabilities. One unusual suggestion, made by creationist Duane Gish
, is that the crest housed chemical glands that allowed it to throw jets of chemical "fire" at enemies, similar to the modern-day bombardier beetle
.
Most of these hypotheses have been discredited or rejected. For example, there is no hole at the end of the crest for a snorkeling function. There are no muscle scars for a proboscis and it is dubious that an animal with a beak would need one. As a proposed airlock, it would not have kept out water. The proposed air reservoir would have been insufficient for an animal the size of Parasaurolophus. Other hadrosaurids had large heads without needing large hollow crests to serve as attachment points for supporting ligaments. Also, none of the proposals explain why the crest has such a shape, why other lambeosaurines should have crests that look much different but perform a similar function, how crestless or solid-crested hadrosaurids got along without such capabilities, or why some hadrosaurids had solid crests. These considerations particularly impact hypotheses based on increasing the capabilities of systems already present in the animal, such as the salt gland and olfaction hypotheses, and indicate that these were not primary functions of the crest. Additionally, work on the nasal cavity of lambeosaurines shows that olfactory nerve
s and corresponding sensory tissue were largely outside the portion of the nasal passages in the crest, so the expansion of the crest had little to do with the sense of smell.
Instead, social and physiological functions have become more supported as function(s) of the crest, focusing on visual
and auditory
identification and communication. As a large object, the crest has clear value as a visual signal, and sets this animal apart from its contemporaries. The large size of hadrosaurid eye sockets
and the presence of sclerotic ring
s in the eyes imply acute vision and diurnal habits, evidence that sight was important to these animals. If, as is commonly illustrated, a skin frill extended from the crest to the neck or back, the proposed visual display would have been even showier. As is suggested by other lambeosaurine skulls, the crest of Parasaurolophus likely permitted both species identification (such as separating it from Corythosaurus or Lambeosaurus) and sexual identification by shape and size.
; Hopson and David B. Weishampel revisited this idea in the 1970s and 1980s. Hopson found that there is anatomical evidence that hadrosaurids had strong hearing. There is at least one example, in the related Corythosaurus, of a slender stapes (reptilian ear bone) in place, which combined with a large space for an eardrum
implies a sensitive middle ear
. Furthermore, the hadrosaurid lagena
is elongate like a crocodilia
n's, indicating that the auditory portion of the inner ear
was well-developed. Weishampel suggested that P. walkeri was able to produce frequencies
of 48 to 240 Hz
, and P. cyrtocristatus (interpreted as a juvenile crest form) 75 to 375 Hz. Based on similarity of hadrosaurid inner ear
s to those of crocodile
s, he also proposed that adult hadrosaurids were sensitive to high frequencies, such as their offspring might produce. According to Weishampel, this is consistent with parents and offspring communicating.
Computer modeling of a well-preserved specimen of P. tubicen, with more complex air passages than those of P. walkeri, has allowed the reconstruction of the possible sound its crest produced. The main path resonates at around 30 Hz, but the complicated sinus anatomy causes peaks and valleys in the sound.
cool. Teresa Maryańska
and Osmólska also proposed thermoregulation at about the same time, and Sullivan and Williamson took further interest. David Evans' 2006 discussion of lambeosaurine crest functions was favorable to the idea, at least as an initial factor for the evolution of crest expansion.
Genus
In 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 ornithopod
Ornithopod
Ornithopods or members of the clade Ornithopoda are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American...
dinosaur
Dinosaur
Dinosaurs 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...
that lived in what is now North America
North America
North 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...
during the Late Cretaceous
Late Cretaceous
The 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...
Period, about 76.5–73 million years ago. It was an herbivore
Herbivore
Herbivores 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...
that walked both as a biped and a quadruped
Quadruped
Quadrupedalism 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"...
. Three species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
are recognized: P. walkeri (the type species
Type species
In 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...
), P. tubicen, and the short-crested P. cyrtocristatus. Remains are known from Alberta
Alberta
Alberta 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...
(Canada
Canada
Canada 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...
), and New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
and Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
(USA). The genus was first described in 1922 by William Parks from a skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
and partial skeleton in Alberta.
Parasaurolophus was a hadrosaurid
Hadrosaurid
Hadrosaurids 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...
, part of a diverse family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of Cretaceous dinosaurs known for their range of bizarre head adornments. This genus is known for its large, elaborate cranial crest, which at its largest forms a long curved tube projecting upwards and back from the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
. Charonosaurus
Charonosaurus
Charonosaurus |Charon]]'s lizard") is the name of a genus of dinosaur whose fossils were discovered by Godefroit, Zan & Jin in 2000 on the south bank of the Amur River, dividing China from Russia.-Description:...
from China
China
Chinese 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...
, which may have been its closest relative, had a similar skull and potentially a similar crest. The crest has been much discussed by scientists; the consensus is that major functions included visual recognition of both species and sex, acoustic resonance, and thermoregulation
Thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...
. It is one of the rarer hadrosaurids, known from only a handful of good specimens.
Description
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
. The thighbone
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
measures 103 cm (40.6 in) long in P. walkeri and is robust for its length when compared to other hadrosaurids. The upper arm
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
and pelvic
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
bones were also heavily built.
Like other hadrosaurids, it was able to walk on either two legs or four. It probably preferred to forage for food on four legs, but ran on two. The neural spines
Spinous process
The spinous process of a vertebra is directed backward and downward from the junction of the laminae , and serves for the attachment of muscles and ligaments. In animals without an erect stance, the process points upward and may slant forward or backward...
of the vertebrae were tall, as was common in lambeosaurines; tallest over the hips, they increased the height of the back. Skin
Integumentary system
The integumentary system is the organ system that protects the body from damage, comprising the skin and its appendages...
impressions are known for P. walkeri, showing uniform tubercle-like scales but no larger structures.
Premaxilla
The 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....
and nasal bone
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 form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
s. The P. walkeri type specimen has a notch in the neural spines near where the crest would hit the back, but this may be a pathology
Pathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
peculiar to this individual. William Parks, who named the genus, hypothesized that a ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...
ran from the crest to the notch to support the head. Although this idea seems unlikely, Parasaurolophus is sometimes restored with a skin flap from the crest to the neck. The crest was hollow, with distinct tubes leading from each nostril to the end of the crest before reversing direction and heading back down the crest and into the skull. The tubes were simplest in P. walkeri, and more complex in P. tubicen, where some tubes were blind and others met and separated. While P. walkeri and P. tubicen had long crests with only slight curvature, P. cyrtocristatus had a short crest with a more circular profile.
Classification
As its name implies, Parasaurolophus was initially thought to be closely related to SaurolophusSaurolophus
Saurolophus is a genus of large hadrosaurine duckbill that lived about 69.5-68.5 million years ago, in the Late Cretaceous of North America and Asia; it is one of the few genera of dinosaurs known from multiple continents. It is distinguished by a spike-like crest which projects up and back...
because of its superficially similar crest. However, it was soon reassessed as a member of the lambeosaurine subfamily of hadrosaurids—Saurolophus is an hadrosaurine. It is usually interpreted as a separate offshoot of the lambeosaurines, distinct from the helmet-crested Corythosaurus
Corythosaurus
Corythosaurus 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...
, Hypacrosaurus
Hypacrosaurus
Hypacrosaurus 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...
, and Lambeosaurus
Lambeosaurus
Lambeosaurus is a genus of hadrosaurid dinosaur that lived about 76 to 75 million years ago, in the Late Cretaceous Period of North America. This bipedal/quadrupedal, herbivorous dinosaur is known for its distinctive hollow cranial crest, which in the best-known species resembled a hatchet...
. Its closest known relative appears to be Charonosaurus
Charonosaurus
Charonosaurus |Charon]]'s lizard") is the name of a genus of dinosaur whose fossils were discovered by Godefroit, Zan & Jin in 2000 on the south bank of the Amur River, dividing China from Russia.-Description:...
, a lambeosaurine with a similar skull (but no complete crest yet) from the Amur region of northeastern China, and the two may form a clade
Clade
A 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...
Parasaurolophini. P. cyrtocristatus, with its short, rounder crest, may be the most basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
of the three known Parasaurolophus species, or it may represent subadult
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...
or female specimens of P. tubicen.
Discovery and naming
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
para/παρα "beside" or "near", saurus/σαυρος "lizard" and lophos/λοφος "crest". It is based on
Holotype
A 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...
ROM
Royal Ontario Museum
The Royal Ontario Museum is a museum of world culture and natural history in Toronto, Ontario, Canada. With its main entrance facing Bloor Street in Downtown Toronto, the museum is situated north of Queen's Park and east of Philosopher's Walk in the University of Toronto...
768, a skull and partial skeleton missing most of the tail and the hind legs below the knees, which was found by a field party from the University of Toronto
University of Toronto
The University of Toronto is a public research university in Toronto, Ontario, Canada, situated on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution of higher learning in Upper Canada...
in 1920 near Sand Creek along the Red Deer River
Red Deer River
The 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, Canada. These rocks are now known as the Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
-age Upper Cretaceous Dinosaur Park Formation
Dinosaur Park Formation
The 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...
. William Parks named the specimen P. walkeri in honor of Sir Byron Edmund Walker
Byron Edmund Walker
Sir Byron Edmund Walker, CVO was a Canadian banker. He was the president of the Canadian Bank of Commerce from 1907 to 1924, and a generous patron of the arts, helping to found and nurture many of Canada's cultural and educational institutions, including the University of Toronto, National Gallery...
, Chairman of the Board of Trustees of the Royal Ontario Museum
Royal Ontario Museum
The Royal Ontario Museum is a museum of world culture and natural history in Toronto, Ontario, Canada. With its main entrance facing Bloor Street in Downtown Toronto, the museum is situated north of Queen's Park and east of Philosopher's Walk in the University of Toronto...
. Parasaurolophus remains are rare in Alberta, with only one other partial skull from (probably) the Dinosaur Park Formation, and three Dinosaur Park specimens lacking skulls, possibly belonging to the genus. In some faunal lists, there is a mention of possible P. walkeri material in the Hell Creek Formation
Hell Creek Formation
The Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana...
of Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
, a rock unit of late Maastrichtian
Maastrichtian
The 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. This occurrence is not noted by Sullivan and Williamson in their 1999 review of the genus, and has not been further elaborated upon elsewhere.
In 1921, Charles H. Sternberg
Charles Hazelius Sternberg
Charles Hazelius Sternberg , was an American fossil collector and amateur paleontologist. His older brother, Dr. George M. Sternberg was a military surgeon assigned to Fort Harker near Ellsworth, Kansas and brought the rest of Sternberg family to Kansas to live on his ranch about 1868...
recovered a partial skull (PMU
Uppsala University
Uppsala University is a research university in Uppsala, Sweden, and is the oldest university in Scandinavia, founded in 1477. It consistently ranks among the best universities in Northern Europe in international rankings and is generally considered one of the most prestigious institutions of...
.R1250) from what is now known as the slightly younger Kirtland Formation
Kirtland Formation
The Kirtland Formation is a sedimentary geological formation. It is the product of alluvial muds and overbank sand deposits from the many channels draining the coastal plain that existed on the inland seashore of North America, in the late Cretaceous period. It overlies the Fruitland Formation...
in San Juan County
San Juan County, New Mexico
-2010:Whereas according to the 2010 U.S. Census Bureau:*51.6% White*0.6% Black*36.6% Native American*0.4% Asian*0.1% Native Hawaiian or Pacific Islander*3.5% Two or more races*7.2% Other races*19.1% Hispanic or Latino -2000:...
, New Mexico. This specimen was sent to Uppsala
Uppsala
- Economy :Today Uppsala is well established in medical research and recognized for its leading position in biotechnology.*Abbott Medical Optics *GE Healthcare*Pfizer *Phadia, an offshoot of Pharmacia*Fresenius*Q-Med...
, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
, where Carl Wiman
Carl Wiman
Carl Wiman was a Swedish paleontologist and the first professor of paleontology at Uppsala University. He published on a variety of topics, including extinct penguins, and dinosaur fossils sent to Sweden from China and the San Juan Basin of New Mexico...
described it as a second species, P. tubicen, in 1931. The specific epithet is derived from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
tǔbǐcěn "trumpeter". A second, nearly complete P. tubicen skull (NMMNH
New Mexico Museum of Natural History and Science
The New Mexico Museum of Natural History and Science is a natural history and science museum in Albuquerque, New Mexico near Old Town Albuquerque. The Museum was founded in 1986....
P-25100) was found in New Mexico in 1995. Using computed tomography
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
of this skull, Robert Sullivan and Thomas Williamson gave the genus a monograph
Monograph
A monograph is a work of writing upon a single subject, usually by a single author.It is often a scholarly essay or learned treatise, and may be released in the manner of a book or journal article. It is by definition a single document that forms a complete text in itself...
ic treatment in 1999, covering aspects of its anatomy and taxonomy, and the functions of its crest. Williamson later published an independent review of the remains, disagreeing with the taxonomic conclusions.
John Ostrom
John Ostrom
John H. Ostrom was an American paleontologist who revolutionized modern understanding of dinosaurs in the 1960s, when he demonstrated that dinosaurs are more like big non-flying birds than they are like lizards , an idea first proposed by Thomas Henry Huxley in the 1860s, but which had garnered...
described another good specimen (FMNH
Field Museum of Natural History
The Field Museum of Natural History is located in Chicago, Illinois, USA. It sits on Lake Shore Drive next to Lake Michigan, part of a scenic complex known as the Museum Campus Chicago...
P27393) from New Mexico as P. cyrtocristatus in 1961. It includes a partial skull with a short, rounded crest, and much of the postcrania
Postcrania
Postcrania[p] in zoology and vertebrate paleontology refers to all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g...
l skeleton except for the feet, neck, and parts of the tail. Its specific name is derived from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
curtus "shortened" and cristatus "crested". The specimen was found in either the top of the Fruitland Formation
Fruitland Formation
The Fruitland Formation is a sedimentary geological formation containing layers of sandstone, shale, and coal. It was laid down in marshy delta conditions, with poor drainage and frequent flooding, under a warm, humid and seasonal climate...
or, more likely, the base of the overlying Kirtland Formation. The range of this species was expanded in 1979, when David B. Weishampel and James A. Jensen
James A. Jensen
James A. Jensen , was an American paleontologist. His extensive collecting program at BYU in the Utah-Colorado region which spanned 23 years was comparable in terms of the number of specimens collected to that of Barnum Brown during the early 20th century. He was given the name "Dinosaur Jim"...
described a partial skull with a similar crest (BYU
Brigham Young University
Brigham Young University is a private university located in Provo, Utah. It is owned and operated by The Church of Jesus Christ of Latter-day Saints , and is the United States' largest religious university and third-largest private university.Approximately 98% of the university's 34,000 students...
2467) from the Campanian-age Kaiparowits Formation
Kaiparowits Formation
The Kaiparowits Formation is a sedimentary rock formation found in the Kaiparowits Plateau in Grand Staircase-Escalante National Monument, in the southern part of Utah in the western United States. It is over 2800 feet thick, and is Campanian in age...
of Garfield County
Garfield County, Utah
Garfield County is a county located in the U.S. state of Utah. As of 2000 the population was 4,735. It was named for James A. Garfield, President of the United States in 1881. Its county seat and largest city is Panguitch.-Geography:...
, Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
. Since then, another skull has been found in Utah with the short/round P. cyrtocristatus crest morphology.
Species
The type speciesType species
In 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...
P. walkeri, from Alberta, is known from a single definitive specimen from the Dinosaur Park Formation
Dinosaur Park Formation
The 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...
, though others from the Dinosaur Park probably belong to it. It differs from P. tubicen by having simpler tubes in its crest, and from P. cyrtocristatus by having a long, unrounded crest and a longer upper arm
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
than forearm
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
. It lived between 76.5 and 75.3 million years ago.
P. tubicen, from New Mexico, is known from the remains of at least three individuals. It is the largest species, with more complex air passages in its crest than P. walkeri, and a longer, straighter crest than P. cyrtocristatus. P. tubicen is known only from the De-na-zin Member of the Kirtland Formation
Kirtland Formation
The Kirtland Formation is a sedimentary geological formation. It is the product of alluvial muds and overbank sand deposits from the many channels draining the coastal plain that existed on the inland seashore of North America, in the late Cretaceous period. It overlies the Fruitland Formation...
, and lived about 73.4–73 million years ago, making it the most recent species.
P. cyrtocristatus, from the Kaiparowits
Kaiparowits Formation
The Kaiparowits Formation is a sedimentary rock formation found in the Kaiparowits Plateau in Grand Staircase-Escalante National Monument, in the southern part of Utah in the western United States. It is over 2800 feet thick, and is Campanian in age...
and Fruitland Formation
Fruitland Formation
The Fruitland Formation is a sedimentary geological formation containing layers of sandstone, shale, and coal. It was laid down in marshy delta conditions, with poor drainage and frequent flooding, under a warm, humid and seasonal climate...
s of New Mexico and Utah, is known from three possible specimens. It lived 75.5–74.5 million years ago, and is the smallest species, with a short rounded crest. Its small size and the form of its crest have led several scientists to suggest that it represents juveniles or females of P. tubicen, though P. tubicen lived at least one million years later. As noted by Thomas Williamson, the type material of P. cyrtocristatus is about 72% the size of P. tubicen, close to the size at which other lambeosaurines are interpreted to begin showing definitive sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in their crests (~70% of adult size). However, this position has been rejected in recent reviews of lambeosaurines.
Paleoecology
Dinosaur Park Formation
The 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...
, was a member of a diverse and well-documented fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
of prehistoric animals, including well-known dinosaurs such as the horned
Ceratopsidae
Ceratopsidae is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus...
Centrosaurus
Centrosaurus
Centrosaurus is a genus of herbivorous ceratopsian dinosaurs from the late Cretaceous of Canada. Their remains have been found in the Dinosaur Park Formation and uppermost Oldman Formation, dating from 76.5 to 75.5 million years ago....
and Chasmosaurus
Chasmosaurus
Chasmosaurus is a genus of ceratopsid dinosaur from the Upper Cretaceous Period of North America. Its name means 'opening lizard', referring to the large openings in its frill . With a length of and a weight of , Chasmosaurus was a ceratopsian of average size...
; fellow duckbills Gryposaurus
Gryposaurus
Gryposaurus was a genus of duckbilled dinosaur that lived about 83 to 75.5 million years ago, in the Late Cretaceous of North America...
and Corythosaurus; tyrannosaurid Gorgosaurus
Gorgosaurus
Gorgosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, between about 76.5 and 75 million years ago. Fossil remains have been found in the Canadian province of Alberta and possibly the U.S. state of Montana....
; and armored
Ankylosauridae
An 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...
Edmontonia
Edmontonia
Edmontonia 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:...
, Euoplocephalus
Euoplocephalus
Euoplocephalus 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...
and Dyoplosaurus
Dyoplosaurus
Dyoplosaurus is the name given to a genus of ankylosaurid dinosaur. It lived during the Late Cretaceous near what is now the Red Deer River in Alberta, Canada and was named by William Parks in 1924, based on holotype ROM 784, a partial skeleton including parts of the skull and lower jaws.The type...
. It was a rare constituent of this fauna. The Dinosaur Park Formation is interpreted as a low-relief setting of river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s and floodplain
Floodplain
A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge...
s that became more swamp
Swamp
A swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types of swamp are "true" or swamp...
y and influenced by marine
Ocean
An 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...
conditions over time as the Western Interior Seaway
Western Interior Seaway
The 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...
transgressed
Transgression (geology)
A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused either by the land sinking or the ocean basins filling with water...
westward. The climate
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
was warmer than present-day Alberta, without frost
Frost
Frost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air as well as below the freezing point of water. Frost crystals' size differ depending on time and water vapour available. Frost is also usually...
, but with wetter and drier seasons. Conifers were apparently the dominant canopy plants, with an understory
Understory
Understory is the term for the area of a forest which grows at the lowest height level below the forest canopy. Plants in the understory consist of a mixture of seedlings and saplings of canopy trees together with understory shrubs and herbs...
of fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s, tree ferns, and angiosperms.
Some of the less common hadrosaurs in the Dinosaur Park Formation of Dinosaur Provincial Park, such as Parasaurolophus, may represent the remains of individuals who died while migrating through the region. They might also have had a more upland habitat where they may have nested or fed. The presence of Parasaurolophus and Kritosaurus in northern latitude fossil sites may represent faunal exchange between otherwise distinct northern and southern biomes in Late Cretaceous North America. Both taxa are uncommon outside of the southern biome, where, along with Pentaceratops
Pentaceratops
Pentaceratops is a genus of ceratopsid dinosaur from the late Cretaceous Period of what is now North America. The appearance of Pentaceratops sternbergii in the fossil record marks the end of the Judithian land vertebrate age and the start of the Kirtlandian...
, they are predominate members of the fauna.
In New Mexico and Utah, the species P. cyrtocristatus shared its environment with the horned ceratopsians Utahceratops
Utahceratops
Utahceratops is a genus of herbivorous ceratopsian dinosaur. It is a chasmosaurine ceratopsian which lived during the Late Cretaceous period in what is now Utah. Its fossils have been recovered from the Kaiparowits Formation. It was first named by Scott D. Sampson, Mark A. Loewen, Andrew A....
, Kosmoceratops
Kosmoceratops
Kosmoceratops is a genus of herbivorous chasmosaurine ceratopsian dinosaur, which lived during the Late Cretaceous period in the part of the island continent Laramidia that is now Utah, United States...
, and Pentaceratops
Pentaceratops
Pentaceratops is a genus of ceratopsid dinosaur from the late Cretaceous Period of what is now North America. The appearance of Pentaceratops sternbergii in the fossil record marks the end of the Judithian land vertebrate age and the start of the Kirtlandian...
, and the coelurosaur Ornithomimus
Ornithomimus
Ornithomimus 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 the tyrannosaur Teratophoneus
Teratophoneus
Teratophoneus is a genus of carnivorous tyrannosaurid theropod dinosaur which lived during the late Cretaceous period in what is now Utah, USA. It is known from an incomplete skull and postcranial skeleton recovered from the Kaiparowits Formation. Teratophoneus was named by Thomas D. Carr, Thomas E...
.
The last and largest of the Parasaurolophus species, P. tubicen, lived in New Mexico alongside the large sauropod Alamosaurus
Alamosaurus
Alamosaurus is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now North America. It was a large quadrupedal herbivore. Isolated vertebrae and limb bones indicate that it reached sizes comparable to Argentinosaurus and Puertasaurus, which would make it the...
, duckbill Kritosaurus
Kritosaurus
Kritosaurus is an incompletely known but historically important genus of hadrosaurid dinosaur. It lived about 73 million years ago, in the Late Cretaceous of North America...
, horned Pentaceratops, armored Nodocephalosaurus
Nodocephalosaurus
Nodocephalosaurus is a genus of herbivorous ankylosaurine ankylosaurid dinosaur from Upper Cretaceous deposits of San Juan Basin, New Mexico. The holotype was recovered from the Late Campanian De-na-zin Member of the Kirtland Formation and consists of an incomplete skull...
, Saurornitholestes
Saurornitholestes
Saurornitholestes is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Alberta, Montana and New Mexico....
, and the tyrannosaurid Bistahieversor
Bistahieversor
Bistahieversor is a genus of tyrannosauroid dinosaur. Bistahieversor existed around 75 million years ago during the Late Cretaceous....
. The Kirtland Formation is interpreted as river floodplains appearing after a retreat of the Western Interior Seaway. Conifers were the dominant plants, and chasmosaurine
Ceratopsidae
Ceratopsidae is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus...
horned dinosaurs were apparently more common than hadrosaurids.
Feeding
As a hadrosaurid, Parasaurolophus was a large bipedal/quadrupedal herbivore, eating plantPlant
Plants 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 with a sophisticated skull that permitted a grinding motion analogous to chewing
Mastication
Mastication 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...
. Its teeth
Tooth
Teeth 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 being replaced; they were packed into dental batteries containing hundreds of teeth, only a relative handful of which were in use at any time. It used its beak to crop plant material, which was held in the jaws by a cheek
Cheek
Cheeks 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. Vegetation could have been taken from the ground up to a height of around 4 meters (13 ft). As noted by Bob Bakker
Robert T. Bakker
Robert T. Bakker is an American paleontologist who helped reshape modern theories about dinosaurs, particularly by adding support to the theory that some dinosaurs were endothermic...
, lambeosaurines have narrower beaks than hadrosaurines, implying that Parasaurolophus and its relatives could feed more selectively than their broad-beaked, crestless counterparts.
Cranial crest
Many hypotheses have been advanced as to what functions the cranial crest of Parasaurolophus performed, but most have been discredited. It is now believed that it may have had several functions: visual display for identifying species and sex, sound amplification for communication, and thermoregulation. It is not clear which was most significant at what times in the evolution of the crest and its internal nasal passages.Differences between species and growth stages
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
characteristic in adults. James Hopson
James Hopson
James 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...
, one of the first researchers to describe lambeosaurine crests in terms of such distinctions, suggested that P. cyrtocristatus, with its small crest, was the female form of P. tubicen. Thomas Williamson suggested it was the juvenile
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...
form. Neither hypothesis became widely accepted. As only six good skulls and one juvenile braincase are known, additional material will help clear up these potential relationships. Williamson noted that in any case, juvenile Parasaurolophus probably had small, rounded crests like P. cyrtocristatus, that probably grew faster as individuals approached sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
. Recent restudy of a juvenile braincase previously assigned to Lambeosaurus, now assigned to Parasaurolophus, provides evidence that a small tubular crest was present in juveniles. This specimen preserves a small upward flaring of the frontal bone
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
s that was similar to but smaller than what is seen in adult specimens; in adults, the frontals formed a platform that supported the base of the crest. This specimen also indicates that the growth of the crest in Parasaurolophus and the facial profile of juvenile individuals differed from the Corythosaurus-Hypacrosaurus-Lambeosaurus model, in part because the crest of Parasaurolophus lacks the thin bony 'coxcomb' that makes up the upper portion of the crest of the other three lambeosaurines.
Rejected hypotheses about function
Many early suggestions focused on adaptations for an aquatic lifestyle, following the hypothesis that hadrosaurids were amphibious, a common line of thought until the 1960s. Thus, Alfred Sherwood Romer proposed it served as a snorkel, Martin Wilfarth that it was an attachment for a mobile proboscisProboscis
A proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In simpler terms, a proboscis is the straw-like mouth found in several varieties of species.-Etymology:...
used as a breathing tube or for food gathering, Charles M. Sternberg
Charles Mortram Sternberg
Charles M. Sternberg 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...
that it served as an airtrap to keep water out of the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s, and Ned Colbert
Edwin Harris Colbert
Edwin Harris Colbert was a distinguished American vertebrate paleontologist and prolific researcher and author. He received his A.B. from the University of Nebraska, then his Masters and Ph.D. from Columbia University, finishing in 1935.Born in Clarinda, Iowa, he grew up in Maryville, Missouri...
that it served as an air reservoir for prolonged stays underwater.
Other proposals were more physical in nature. As mentioned above, William Parks suggested that it was joined to the vertebrae with ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...
s or muscles, and helped with moving and supporting the head. Othenio Abel proposed it was used as a weapon in combat among members of the same species, and Andrew Milner suggested that it could be used as a foliage deflector, like the helmet crest (called a 'casque') of the cassowary
Cassowary
The cassowaries are ratites, very large flightless birds in the genus Casuarius native to the tropical forests of New Guinea, nearby islands and northeastern Australia. There are three extant species recognized today...
. Still other proposals made housing specialized organs the major function. Halszka Osmólska
Halszka Osmólska
Halszka Osmólska was a Polish paleontologist who had specialized in Mongolian dinosaurs.She was born in Poznań. A member of the 1965 and 1970 Polish–Mongolian expeditions to the Gobi Desert, she described many finds from these rocks, often with Teresa Maryańska...
suggested that it housed salt gland
Salt gland
The salt gland is an organ for excreting excess salts. It is found in elasmobranchs, seabirds, and some reptiles. In sharks, salt glands are found in the rectum, but in birds and reptiles, they are found in or on the skull, in the area of the eyes, nostrils or mouth. In crocodiles, the salt is...
s, and John Ostrom suggested that it housed expanded areas for olfactory tissue
Olfactory epithelium
The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smell. In humans, it measures about 1 square centimetre and lies on the roof of the nasal cavity about 7 cm above and behind the nostrils...
and much improved sense of smell
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
of the lambeosaurines, which had no obvious defensive capabilities. One unusual suggestion, made by creationist Duane Gish
Duane Gish
Duane Tolbert Gish is an American biochemist and a prominent member of the creationist movement. Gish is a former vice-president of the Institute for Creation Research and the author of numerous publications on the subject of creation science. Gish has been called "creationism's T.H...
, is that the crest housed chemical glands that allowed it to throw jets of chemical "fire" at enemies, similar to the modern-day bombardier beetle
Bombardier beetle
Bombardier beetles are ground beetles in the tribes Brachinini, Paussini, Ozaenini, or Metriini—more than 500 species altogether—which are most notable for the defense mechanism that gives them their name: When disturbed, the beetle ejects a noxious chemical spray in a rapid burst of pulses from...
.
Most of these hypotheses have been discredited or rejected. For example, there is no hole at the end of the crest for a snorkeling function. There are no muscle scars for a proboscis and it is dubious that an animal with a beak would need one. As a proposed airlock, it would not have kept out water. The proposed air reservoir would have been insufficient for an animal the size of Parasaurolophus. Other hadrosaurids had large heads without needing large hollow crests to serve as attachment points for supporting ligaments. Also, none of the proposals explain why the crest has such a shape, why other lambeosaurines should have crests that look much different but perform a similar function, how crestless or solid-crested hadrosaurids got along without such capabilities, or why some hadrosaurids had solid crests. These considerations particularly impact hypotheses based on increasing the capabilities of systems already present in the animal, such as the salt gland and olfaction hypotheses, and indicate that these were not primary functions of the crest. Additionally, work on the nasal cavity of lambeosaurines shows that olfactory nerve
Olfactory nerve
The olfactory nerve, or cranial nerve I, is the first of twelve cranial nerves. It is instrumental in the sense of smell. Derived from the embryonic nasal placode, the olfactory nerve is capable of regeneration.-Anatomy:...
s and corresponding sensory tissue were largely outside the portion of the nasal passages in the crest, so the expansion of the crest had little to do with the sense of smell.
Social functions
Visual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...
and auditory
Hearing (sense)
Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
identification and communication. As a large object, the crest has clear value as a visual signal, and sets this animal apart from its contemporaries. The large size of hadrosaurid eye sockets
Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...
and the presence of sclerotic ring
Sclerotic ring
Sclerotic 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 in the eyes imply acute vision and diurnal habits, evidence that sight was important to these animals. If, as is commonly illustrated, a skin frill extended from the crest to the neck or back, the proposed visual display would have been even showier. As is suggested by other lambeosaurine skulls, the crest of Parasaurolophus likely permitted both species identification (such as separating it from Corythosaurus or Lambeosaurus) and sexual identification by shape and size.
Sounding function
However, the external appearance of the crest does not correspond to the complex internal anatomy of the nasal passages, which suggests another function accounted for usage of the internal space. Carl Wiman was the first to propose, in 1931, that the passages served an auditory signaling function, like a crumhornCrumhorn
The crumhorn is a musical instrument of the woodwind family, most commonly used during the Renaissance period. In modern times, there has been a revival of interest in Early Music, and crumhorns are being played again....
; Hopson and David B. Weishampel revisited this idea in the 1970s and 1980s. Hopson found that there is anatomical evidence that hadrosaurids had strong hearing. There is at least one example, in the related Corythosaurus, of a slender stapes (reptilian ear bone) in place, which combined with a large space for an eardrum
Eardrum
The eardrum, or tympanic membrane, is a thin membrane that separates the external ear from the middle ear in humans and other tetrapods. Its function is to transmit sound from the air to the ossicles inside the middle ear. The malleus bone bridges the gap between the eardrum and the other ossicles...
implies a sensitive middle ear
Middle ear
The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear has...
. Furthermore, the hadrosaurid lagena
Lagena
The extremities of the ductus cochlearis are closed; the upper is termed the lagena and is attached to the cupula at the upper part of the helicotrema; the lower is lodged in the recessus cochlearis of the vestibule.- In fish and amphibians :...
is elongate like a crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
n's, indicating that the auditory portion of the inner ear
Inner ear
The inner ear is the innermost part of the vertebrate ear. In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts:...
was well-developed. Weishampel suggested that P. walkeri was able to produce frequencies
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
of 48 to 240 Hz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
, and P. cyrtocristatus (interpreted as a juvenile crest form) 75 to 375 Hz. Based on similarity of hadrosaurid inner ear
Inner ear
The inner ear is the innermost part of the vertebrate ear. In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts:...
s to those of crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...
s, he also proposed that adult hadrosaurids were sensitive to high frequencies, such as their offspring might produce. According to Weishampel, this is consistent with parents and offspring communicating.
Computer modeling of a well-preserved specimen of P. tubicen, with more complex air passages than those of P. walkeri, has allowed the reconstruction of the possible sound its crest produced. The main path resonates at around 30 Hz, but the complicated sinus anatomy causes peaks and valleys in the sound.
Cooling function
The large surface area and vascularization of the crest also suggests a thermoregulatory function. P.E. Wheeler first suggested this use in 1978 as a way to keep the brainBrain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
cool. Teresa Maryańska
Teresa Maryanska
Teresa Maryańska is a Polish paleontologist who has specialized in Mongolian dinosaurs, particularly pachycephalosaurians and ankylosaurians. A member of the 1964, 1965, 1970, and 1971 Polish–Mongolian expeditions to the Gobi Desert, she has described many finds from these rocks, often with...
and Osmólska also proposed thermoregulation at about the same time, and Sullivan and Williamson took further interest. David Evans' 2006 discussion of lambeosaurine crest functions was favorable to the idea, at least as an initial factor for the evolution of crest expansion.
External links
- Scientists Use Digital Paleontology to Produce Voice of Parasaurolophus Dinosaur; from Sandia National Laboratories.
- Restorations of P. walkeri and P. cyrtocristatus, to the same scale, by Scott Hartman; at Skeletal Drawing.com.
