Lambeosaurus
Encyclopedia
Lambeosaurus is a genus
of hadrosaurid
dinosaur
that lived about 76 to 75 million years ago, in the Late Cretaceous
Period (Campanian
) of North America
. This bipedal/quadruped
al, herbivorous
dinosaur is known for its distinctive hollow cranial crest, which in the best-known species resembled a hatchet
. Several possible species have been named, from Alberta
(Canada
), Montana
(USA), and Baja California
(Mexico
), but only the two Canadian species are currently well known. At about 15 meters (50 ft) long, the possible Mexican species "L." laticaudus was one of the longest
ornithischians. The other species were more modestly sized.
Lambeosaurus was belatedly described in 1923 by William Parks, over twenty years after the first material was studied by Lawrence Lambe
. The genus has had a complicated taxonomic
history, in part because small-bodied crested hadrosaurids now recognized as juveniles
were once thought to belong to their own genera and species
. Currently, the various skulls assigned to the type species
L. lambei are interpreted as showing age differences and sexual dimorphism
. Lambeosaurus was closely related to the better known Corythosaurus
, which is found in slightly older rocks, as well as the less well-known genera Hypacrosaurus
and Olorotitan
. All had unusual crests, which are now generally assumed to have served social functions like noisemaking and recognition.
Lambeosaurus, best known through L. lambei, was quite similar to the more famous Corythosaurus
in everything but the form of the head adornment. Compared to Corythosaurus, the crest of Lambeosaurus was shifted forward, and the hollow nasal passages within were at the front of the crest and stacked vertically. It also can be differentiated from Corythosaurus by its lack of forking nasal
processes
making up part of the sides of the crest, which is the only way to tell juveniles of the two genera apart: the crests took on their distinctive forms as the animals aged.
In build, Lambeosaurus was like other hadrosaurids, and could move on both two legs and all fours, as shown by footprints of related animals. It had a long tail stiffened by ossified tendons that prevented it from drooping. The hands had four fingers, lacking the innermost finger
of the generalized five-fingered tetrapod
hand, while the second, third, and fourth fingers were bunched together and bore hooves
, suggesting the animal could use the hands for support. The fifth finger
was free and could be used to manipulate objects. Each foot had only the three central toes.
The most distinctive feature, the crest, was different in the two well-known species. In L. lambei, it had a hatchet-like shape when the dinosaur was full-grown, and was somewhat shorter and more rounded in specimens interpreted as females. The "hatchet blade" projected in front of the eyes, and the "handle" was a solid bony rod that jutted out over the back of the skull. The "hatchet blade" had two sections: the uppermost portion was a thin bony "coxcomb" that grew out relatively late in life, when an individual neared adulthood; and the lower portion held hollow spaces that were continuations of the nasal passages. In L. magnicristatus, the "handle" was greatly reduced, and the "blade" expanded, forming a tall, exaggerated pompadour
-like crest. This crest is damaged in the best overall specimen, and only the front half remains. In the lesser-known species "L." laticaudus and L. paucidens the crest is not currently known. However, "L." laticaudus can be recognized by its great size and the tall profile of its tail, which had elongated chevron
s and vertebral spines
like those of Hypacrosaurus
.
The Canadian species of Lambeosaurus appear to have been similar in size to Corythosaurus, and thus around 9.4 m long (31 ft), but "L." laticaudus is estimated at between 15 m (50 ft) and 16.5 m (54.1 ft) long, with a weight of up to 23 metric tons
(25 ton
s). Impressions of the scales
are known for several specimens; a specimen now assigned to L. lambei had a thin skin
with uniform, polygonal scute
s distributed in no particular order on the neck, torso, and tail. Similar scalation is known from the neck, forelimb, and foot of a specimen of L. magnicristatus, whereas the tail of "L." laticaudus had some small bony bits embedded among large hexagonal and smaller rounded scales.
of the Lambeosaurinae
, the subfamily of hadrosaurids that had hollow skull crests. Among the lambeosaurines, it is closely related to Corythosaurus and Hypacrosaurus
, with little separating them but crest form. The relationships among these dinosaur genera are difficult to pick out. Internet classifications sometimes include all three in the tribe Lambeosaurini, but such a tribe has not been formally defined. Instead, the equivalent clade
Corythosaurini has been adopted in publications, including the most recent phylogeny
, presented by David Evans and Robert Reisz in their redescription of L. magnicristatus. This examination indicated that Lambeosaurus is the sister taxon
to a clade made up of Corythosaurus, Hypacrosaurus, and the Russia
n genus Olorotitan
; these lambeosaurines, with Nipponosaurus
, make up Corythosaurini.
Lambeosaurus has a complicated taxonomic
history, beginning in 1902 with Lawrence Lambe
's naming of hadrosaurid limb material and other bones (originally GSC 419) from Alberta as Trachodon marginatus
. Paleontologists began finding better remains of hadrosaurids from the same rocks in the 1910s, in what is now known as the late Campanian
-age (Upper Cretaceous) Dinosaur Park Formation
. Lambe assigned two new skulls to T. marginatus, and based on the new information, coined the genus Stephanosaurus
for the species in 1914. Unfortunately, there was very little to associate the skulls with the scrappy earlier marginatus material, so in 1923 William Parks proposed a new genus and species for the skulls, with both generic and specific names honoring Lambe: Lambeosaurus lambei (type specimen
NMC
2869, originally GSC 2869).
(GSC 1092) from the Dinosaur Park Formation described by Henry Fairfield Osborn
in 1902. It was referred to as Trachodon altidens by Lambe, and the name Didanodon seems to have rapidly fallen into obscurity, as it is not mentioned in Richard Swann Lull and Nelda Wright's influential 1942 monograph
on North American hadrosaurids.
In 1920, William Diller Matthew
used the name Procheneosaurus
(no species name) in a caption for a photograph of a skeleton at the American Museum of Natural History
, from the Dinosaur Park Formation (AMNH
5340). Parks believed that the procedure and description were inadequate for the name to be considered valid, and to address the situation, he coined the genus Tetragonosaurus. Into this genus he placed the type species
T. praeceps (based on ROM
3577) and a second species T. erectofrons (based on ROM 3578) for small skulls from the Dinosaur Park Formation, and assigned Matthew's Procheneosaurus skeleton to T. praeceps. Charles M. Sternberg
followed in 1935 by adding the slightly larger T. cranibrevis, based on GSC (now NMC) 8633. The use of Tetragonosaurus was rejected by Lull in favor of Procheneosaurus. In 1942 he and Wright transferred the Tetragonosaurus species and, tentatively, Trachodon altidens, to Procheneosaurus, with P. praeceps serving as the type species. This usage was generally followed until 1975, when Peter Dodson
showed that the "cheneosaurs" were actually juveniles
of other dinosaurs. Procheneosaurus praeceps and altidens are considered probable synonyms
of Lambeosaurus lambei, although both predate that name.
The "procheneosaurs" weren't the only crested duckbills being studied and named in the early 1900s. It was then the accepted practice to name genera and species for what is now seen as more likely individual variation, variation due to age or sex, or distortion from fossilization. Three more species were named during this period that relate to Lambeosaurus, all in 1935. Sternberg, in the same paper as T. cranibrevis, named a skull and partial skeleton (GSC—now NMC—8705) L. magnicristatum (corrected to magnicristatus), and a smaller skull (GSC—now NMC—8703) L. clavinitialis, with a less prominent crest and reduced spine pointing from the back. Parks contributed Corythosaurus frontalis, based on skull GSC 5853 (now ROM 869), which differed from the well-known tall, straight, rounded crest of other specimens of Corythosaurus by having a low crest cocked forward.
noted that an old species named by Othniel Charles Marsh
, Hadrosaurus
paucidens, based on USNM
5457, a partial maxilla
and squamosal
from the Judith River Formation
of Fergus County
, Montana
, was probably a specimen of Lambeosaurus.
In 1975, Peter Dodson, examining why there should be so many species and genera of lambeosaurine duckbills within such a short geological time frame and small area, published the results of a morphometric
study in which he measured dozens of skulls. He found that many of the species had been based on remains that were better interpreted as juveniles or different sexes. For Lambeosaurus, he found that L. clavinitialis was probably the female of L. lambei, and Corythosaurus frontalis and Procheneosaurus praeceps were probably its juveniles. L. magnicristatus was different enough to warrant its own species. He interpreted Procheneosaurus cranibrevis and P. erectofrons as juvenile corythosaurs. However, restudy of the Procheneosaurus/Tetragonosaurus remains indicates that within species, assignments had become confused, and the type specimen of P. cranibrevis was a Lambeosaurus juvenile, whereas others were Corythosaurus, based on the distinctive form of the contact of the nasal bone
with the premaxilla
.
Also during the 1970s, Bill Morris was studying giant lambeosaurine remains from Baja California. He named them ?L. laticaudus in 1981 (type specimen LACM
17715). Morris used a question mark in his work because no complete crest had been found for his species, and without it a definitive assignment could not be made. From what was known of the skull, he considered it to be most like Lambeosaurus. He interpreted this species as water-bound, due to features like its size, its tall and narrow tail (interpreted as a swimming adaptation), and weak hip
articulations, as well as a healed broken thigh bone
that he thought would have been too much of a handicap for a terrestrial animal to have survived long enough to heal.
Two species of Lambeosaurus are currently confirmed valid, with a third widely accepted and a fourth sometimes accepted. L. lambei (Parks, 1923) is known from at least 17 individuals, with seven skulls and partial skeletons and around ten isolated skulls. L. clavinitialis (C.M. Sternberg, 1935), Corythosaurus frontalis (Parks, 1935), and Procheneosaurus praeceps (Parks, 1931) are all regarded as synonyms of L. lambei in the most recent review. It is possible that L. clavinitialis skulls without the backward spine may represent L. magnicristatus individuals instead, although this was rejected in the 2007 redescription of L. magnicristatus. L. magnicristatus (C.M. Sternberg, 1935) is only definitely known from two specimens, both with skulls. Unfortunately, the majority of the articulated skeleton of the type specimen has been lost. Many of the bones were extensively damaged by water while in storage and were discarded before description; other portions of this skeleton have also been lost. Its remains come from slightly younger rocks than L. lambei. The specific name is derived from the Latin
magnus "large" and cristatus "crested", referring to its bony crest. Additionally, Jack Horner
has identified fragmentary lambeosaurine jaws from the Bearpaw Formation
of Montana
as possibly belonging to L. magnicristatus; these represent the first lambeosaurine remains from marine
rocks. The large "L." laticaudus (Morris, 1981), known from disassociated remains from several individuals, is accepted as a potential species as well, although it could instead be a species of Hypacrosaurus. Its validity has been questioned by the describers of Velafrons
, who find its remains to be nondiagnostic but distinct from their genus. The specific name here is derived from the Latin latus "broad" and cauda "tail".
L. paucidens (Marsh, 1889) is regarded as a dubious name
and is listed as Hadrosaurus paucidens in the latest review, although at least one author, Donald F. Glut
, accepts it as a species of Lambeosaurus. In this case, the specific epithet is derived from the Latin pauci- "few" and dens "tooth". The irregularities of Procheneosaurus cranibrevis, and the identity of the type as a juvenile lambeosaur, were recognized in 2005, and thus have not yet entered wide circulation. Finally, Didanodon and Trachodon altidens have received confusing treatment in the most recent review: Didanodon was assigned without comment to Lambeosaurus, yet the species Trachodon altidens was listed separately in a table of dubious names.
Lambeosaurus lambei and L. magnicristatus, from the Dinosaur Park Formation
, were members of a diverse and well-documented fauna
of prehistoric animals that included such well-known dinosaurs as the horned
Centrosaurus
, Styracosaurus
, and Chasmosaurus
, fellow duckbills Prosaurolophus
, Gryposaurus
, Corythosaurus, and Parasaurolophus
, tyrannosaurid Gorgosaurus
, and armored
Edmontonia
and Euoplocephalus
. 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. The anatomically similar L. lambei, L. magnicristatus, and Corythosaurus were separated by time within the formation, based on stratigraphy
. Corythosaurus fossils are known from the lower two-thirds of the Formation, L. lambei fossils are present in the upper third, and L. magnicristatus remains are rare and present only at the very top, where the marine influence was greater.
As a hadrosaurid, Lambeosaurus was a large bipedal/quadrupedal herbivore, eating plant
s with a sophisticated skull that permitted a grinding motion analogous to mammal
ian chewing
. Its teeth
were continually replaced and were packed into dental batteries that each contained over 100 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. Feeding would have been from the ground up to around 4 meters (13 ft) above. As noted by Bob Bakker
, lambeosaurines have narrower beaks than hadrosaurines, implying that Lambeosaurus and its relatives could feed more selectively than their broad-beaked, crestless counterparts.
such as Parasaurolophus and Corythosaurus, Lambeosaurus had a distinctive crest on the top of its head. Its nasal cavity ran back through this crest, making it mostly hollow. Many suggestions have been made for the function or functions of the crest, including housing salt gland
s, improving the sense of smell
, use as a snorkel or air trap, acting as a resonating chamber for making sounds, or being a method for different species or different sexes of the same species to recognize each other. Social functions such as noisemaking and recognition have become the most widely accepted of the various hypotheses.
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. The hadrosaurid sense of hearing
also appears to be strong. 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
, and the hadrosaurid lagena
is elongate like a crocodilia
n's. This indicates that the auditory portion of the inner ear
was well-developed. If used as a noisemaker, the crest could also have provided recognizable differences for different species or sexes, because the differing layouts of the nasal passages corresponding to the different crest shapes would have produced intrinsically different sounds.
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 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...
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 about 76 to 75 million years ago, in 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 (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 ...
) of 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...
. This bipedal/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"...
al, herbivorous
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...
dinosaur is known for its distinctive hollow cranial crest, which in the best-known species resembled a hatchet
Hatchet
A hatchet is a single-handed striking tool with a sharp blade used to cut and split wood...
. Several possible species have been named, 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...
), 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,...
(USA), and Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
(Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
), but only the two Canadian species are currently well known. At about 15 meters (50 ft) long, the possible Mexican species "L." laticaudus was one of the longest
Dinosaur size
Size has been one of the most interesting aspects of dinosaur science to the general public. This article lists the largest and smallest dinosaurs from various groups, sorted in order of weight and length....
ornithischians. The other species were more modestly sized.
Lambeosaurus was belatedly described in 1923 by William Parks, over twenty years after the first material was studied by Lawrence Lambe
Lawrence Lambe
Lawrence Morris Lambe was a Canadian geologist and palaeontologist from the Geological Survey of Canada .His published work, describing the diverse and plentiful dinosaur discoveries from the fossil beds in Alberta, did much to bring dinosaurs into the public eye and helped usher in the Golden...
. The genus has had a complicated taxonomic
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
history, in part because small-bodied crested hadrosaurids now recognized as juveniles
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...
were once thought to belong to their own genera and 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...
. Currently, the various skulls assigned to 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...
L. lambei are interpreted as showing age differences and 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:...
. Lambeosaurus was closely related to the better known 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...
, which is found in slightly older rocks, as well as the less well-known genera 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 Olorotitan
Olorotitan
Olorotitan was a genus of lambeosaurine duckbilled dinosaur from the middle or latest Maastrichtian-age Late Cretaceous Tsagayan Formation beds located in Kundur, Amur Region, Far Eastern Russia. The remains, consisting of a nearly complete skeleton, were described by Pascal Godefroit et al. in...
. All had unusual crests, which are now generally assumed to have served social functions like noisemaking and recognition.
Description
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...
in everything but the form of the head adornment. Compared to Corythosaurus, the crest of Lambeosaurus was shifted forward, and the hollow nasal passages within were at the front of the crest and stacked vertically. It also can be differentiated from Corythosaurus by its lack of forking nasal
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....
processes
Process (anatomy)
In anatomy, a process is a projection or outgrowth of tissue from a larger body. The vertebra has several kinds of processes,such as: transverse process, prezygapophysis, postzygapophysis.-Examples:Examples of processes include:...
making up part of the sides of the crest, which is the only way to tell juveniles of the two genera apart: the crests took on their distinctive forms as the animals aged.
In build, Lambeosaurus was like other hadrosaurids, and could move on both two legs and all fours, as shown by footprints of related animals. It had a long tail stiffened by ossified tendons that prevented it from drooping. The hands had four fingers, lacking the innermost finger
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
of the generalized five-fingered tetrapod
Tetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...
hand, while the second, third, and fourth fingers were bunched together and bore hooves
Hoof
A hoof , plural hooves or hoofs , is the tip of a toe of an ungulate mammal, strengthened by a thick horny covering. The hoof consists of a hard or rubbery sole, and a hard wall formed by a thick nail rolled around the tip of the toe. The weight of the animal is normally borne by both the sole...
, suggesting the animal could use the hands for support. The fifth finger
Little finger
The little finger, often called the pinky in American English, pinkie in Scottish English , or small finger in medicine, is the most ulnar and usually smallest finger of the human hand, opposite the thumb, next to the ring finger.-Muscles:There are four muscles that...
was free and could be used to manipulate objects. Each foot had only the three central toes.
Pompadour (hairstyle)
Pompadour is a tall style of men's haircut which takes its name from Madame de Pompadour.There are Latin variants of the hair style more associated with European and Argentine tango fashion trends and occasionally with late 20th century musical genres such as rockabilly and country.The pompadour...
-like crest. This crest is damaged in the best overall specimen, and only the front half remains. In the lesser-known species "L." laticaudus and L. paucidens the crest is not currently known. However, "L." laticaudus can be recognized by its great size and the tall profile of its tail, which had elongated chevron
Chevron (anatomy)
A chevron is one of a series of bones on the ventral side of the tail in many reptiles, dinosaurs , and some mammals such as kangaroos and manatees....
s and vertebral 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...
like those of 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...
.
The Canadian species of Lambeosaurus appear to have been similar in size to Corythosaurus, and thus around 9.4 m long (31 ft), but "L." laticaudus is estimated at between 15 m (50 ft) and 16.5 m (54.1 ft) long, with a weight of up to 23 metric tons
Tonne
The 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...
(25 ton
Short ton
The short ton is a unit of mass equal to . In the United States it is often called simply ton without distinguishing it from the metric ton or the long ton ; rather, the other two are specifically noted. There are, however, some U.S...
s). Impressions of the scales
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
are known for several specimens; a specimen now assigned to L. lambei had a thin skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
with uniform, polygonal scute
Scute
A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:...
s distributed in no particular order on the neck, torso, and tail. Similar scalation is known from the neck, forelimb, and foot of a specimen of L. magnicristatus, whereas the tail of "L." laticaudus had some small bony bits embedded among large hexagonal and smaller rounded scales.
Classification
Lambeosaurus is the type genusBiological type
In biology, a type is one particular specimen of an organism to which the scientific name of that organism is formally attached...
of the Lambeosaurinae
Lambeosaurinae
Lambeosaurinae 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...
, the subfamily of hadrosaurids that had hollow skull crests. Among the lambeosaurines, it is closely related to Corythosaurus and 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...
, with little separating them but crest form. The relationships among these dinosaur genera are difficult to pick out. Internet classifications sometimes include all three in the tribe Lambeosaurini, but such a tribe has not been formally defined. Instead, the equivalent 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...
Corythosaurini has been adopted in publications, including the most recent phylogeny
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
, presented by David Evans and Robert Reisz in their redescription of L. magnicristatus. This examination indicated that Lambeosaurus is the sister taxon
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
to a clade made up of Corythosaurus, Hypacrosaurus, and the Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
n genus Olorotitan
Olorotitan
Olorotitan was a genus of lambeosaurine duckbilled dinosaur from the middle or latest Maastrichtian-age Late Cretaceous Tsagayan Formation beds located in Kundur, Amur Region, Far Eastern Russia. The remains, consisting of a nearly complete skeleton, were described by Pascal Godefroit et al. in...
; these lambeosaurines, with Nipponosaurus
Nipponosaurus
Nipponosaurus is a lambeosaurine hadrosaurid from Asia.The holotype was discovered in November 1934 during the construction of a hospital for the Kawakami colliery of the Mitsui Mining Company on Karafuto Prefecture , and additional material belonging to the specimen was recovered...
, make up Corythosaurini.
Discovery and history
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
history, beginning in 1902 with Lawrence Lambe
Lawrence Lambe
Lawrence Morris Lambe was a Canadian geologist and palaeontologist from the Geological Survey of Canada .His published work, describing the diverse and plentiful dinosaur discoveries from the fossil beds in Alberta, did much to bring dinosaurs into the public eye and helped usher in the Golden...
's naming of hadrosaurid limb material and other bones (originally GSC 419) from Alberta as Trachodon marginatus
Trachodon
Trachodon is a dubious genus of hadrosaurid dinosaur based on teeth from the Campanian-age Upper Cretaceous Judith River Formation of Montana, U.S.A...
. Paleontologists began finding better remains of hadrosaurids from the same rocks in the 1910s, in what is now known as the late 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...
. Lambe assigned two new skulls to T. marginatus, and based on the new information, coined the genus Stephanosaurus
Stephanosaurus
Stephanosaurus is a dubious genus of hadrosaurid dinosaur, with a complicated taxonomic history.In 1902, Lawrence Lambe named a new set of hadrosaurid limb material and other bones from Alberta as Trachodon marginatus...
for the species in 1914. Unfortunately, there was very little to associate the skulls with the scrappy earlier marginatus material, so in 1923 William Parks proposed a new genus and species for the skulls, with both generic and specific names honoring Lambe: Lambeosaurus lambei (type specimen
Biological type
In biology, a type is one particular specimen of an organism to which the scientific name of that organism is formally attached...
NMC
Canadian Museum of Nature
The Canadian Museum of Nature is a natural history museum in Ottawa, Ontario, Canada. Its collections, which were started by the Geological Survey of Canada in 1856, include all aspects of the intersection of human society and nature, from gardening to gene-splicing...
2869, originally GSC 2869).
New species and procheneosaurs
Although the early workers in Alberta did not recognize it at the time, they were finding the remains of juvenile Lambeosaurus as well. These fossils of small-bodied crested duckbills were interpreted as adults of a distinct lineage of hadrosaurids, the subfamily Cheneosaurinae. The first such animal to be named was Didanodon altidens, a left upper jawMaxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
(GSC 1092) from the Dinosaur Park Formation described by Henry Fairfield Osborn
Henry Fairfield Osborn
Henry Fairfield Osborn, Sr. ForMemRS was an American geologist, paleontologist, and eugenicist.-Early life and career:...
in 1902. It was referred to as Trachodon altidens by Lambe, and the name Didanodon seems to have rapidly fallen into obscurity, as it is not mentioned in Richard Swann Lull and Nelda Wright's influential 1942 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...
on North American hadrosaurids.
William Diller Matthew
William Diller Matthew FRS was a vertebrate paleontologist who worked primarily on mammal fossils....
used the name Procheneosaurus
Procheneosaurus
Procheneosaurus is a disused genus of hadrosaur dinosaur, based on small skulls with low domes in front of the eyes. It is now believed that the remains referred to its various species were from juvenile individuals of multiple genera of crested hadrosaurs...
(no species name) in a caption for a photograph of a skeleton at the American Museum of Natural History
American Museum of Natural History
The 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...
, from the Dinosaur Park Formation (AMNH
American Museum of Natural History
The 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...
5340). Parks believed that the procedure and description were inadequate for the name to be considered valid, and to address the situation, he coined the genus Tetragonosaurus. Into this genus he placed 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...
T. praeceps (based on 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...
3577) and a second species T. erectofrons (based on ROM 3578) for small skulls from the Dinosaur Park Formation, and assigned Matthew's Procheneosaurus skeleton to T. praeceps. 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...
followed in 1935 by adding the slightly larger T. cranibrevis, based on GSC (now NMC) 8633. The use of Tetragonosaurus was rejected by Lull in favor of Procheneosaurus. In 1942 he and Wright transferred the Tetragonosaurus species and, tentatively, Trachodon altidens, to Procheneosaurus, with P. praeceps serving as the type species. This usage was generally followed until 1975, when Peter Dodson
Peter Dodson
Peter 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...
showed that the "cheneosaurs" were actually juveniles
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...
of other dinosaurs. Procheneosaurus praeceps and altidens are considered probable synonyms
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
of Lambeosaurus lambei, although both predate that name.
The "procheneosaurs" weren't the only crested duckbills being studied and named in the early 1900s. It was then the accepted practice to name genera and species for what is now seen as more likely individual variation, variation due to age or sex, or distortion from fossilization. Three more species were named during this period that relate to Lambeosaurus, all in 1935. Sternberg, in the same paper as T. cranibrevis, named a skull and partial skeleton (GSC—now NMC—8705) L. magnicristatum (corrected to magnicristatus), and a smaller skull (GSC—now NMC—8703) L. clavinitialis, with a less prominent crest and reduced spine pointing from the back. Parks contributed Corythosaurus frontalis, based on skull GSC 5853 (now ROM 869), which differed from the well-known tall, straight, rounded crest of other specimens of Corythosaurus by having a low crest cocked forward.
Reconsideration and consolidation
New specimens were not described for many years following the activity of the early 1900s. In 1964 John OstromJohn 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...
noted that an old species named by Othniel Charles Marsh
Othniel Charles Marsh
Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...
, Hadrosaurus
Hadrosaurus
Hadrosaurus 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...
paucidens, based on USNM
National Museum of Natural History
The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. Admission is free and the museum is open 364 days a year....
5457, a partial maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
and squamosal
Squamosal
The squamosal is a bone of the head of higher vertebrates. It is the principal component of the cheek region in the skull, lying below the temporal series and otic notch and bounded anteriorly by postorbital. Posteriorly, the squamosal articulates with the posterior elements of the palatal complex,...
from the Judith River Formation
Judith River Formation
The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the upper Cretaceous, between 80 and 75 million years ago, corresponding to the "Judithian" land vertebrate age...
of Fergus County
Fergus County, Montana
-National protected areas:* Charles M. Russell National Wildlife Refuge * Lewis and Clark National Forest * Upper Missouri River Breaks National Monument -Demographics:...
, 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,...
, was probably a specimen of Lambeosaurus.
In 1975, Peter Dodson, examining why there should be so many species and genera of lambeosaurine duckbills within such a short geological time frame and small area, published the results of a morphometric
Morphometrics
Morphometrics refers to the quantitative analysis of form, a concept that encompasses size and shape. Morphometric analyses are commonly performed on organisms, and are useful in analyzing their fossil record, the impact of mutations on shape, developmental changes in form, covariances between...
study in which he measured dozens of skulls. He found that many of the species had been based on remains that were better interpreted as juveniles or different sexes. For Lambeosaurus, he found that L. clavinitialis was probably the female of L. lambei, and Corythosaurus frontalis and Procheneosaurus praeceps were probably its juveniles. L. magnicristatus was different enough to warrant its own species. He interpreted Procheneosaurus cranibrevis and P. erectofrons as juvenile corythosaurs. However, restudy of the Procheneosaurus/Tetragonosaurus remains indicates that within species, assignments had become confused, and the type specimen of P. cranibrevis was a Lambeosaurus juvenile, whereas others were Corythosaurus, based on the distinctive form of the contact of the 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....
with the premaxilla
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....
.
Natural History Museum of Los Angeles County
The Natural History Museum of Los Angeles County opened in Exposition Park, Los Angeles, California, USA in 1913 as the Museum of History, Science, and Art. The moving force behind it was a museum association founded in 1910. Its distinctive main building, with fitted marble walls and domed and...
17715). Morris used a question mark in his work because no complete crest had been found for his species, and without it a definitive assignment could not be made. From what was known of the skull, he considered it to be most like Lambeosaurus. He interpreted this species as water-bound, due to features like its size, its tall and narrow tail (interpreted as a swimming adaptation), and weak hip
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:...
articulations, as well as a healed broken thigh bone
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...
that he thought would have been too much of a handicap for a terrestrial animal to have survived long enough to heal.
Species
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...
magnus "large" and cristatus "crested", referring to its bony crest. Additionally, Jack Horner
Jack Horner (paleontologist)
John "Jack" R. Horner is an American paleontologist who discovered and named Maiasaura, providing the first clear evidence that some dinosaurs cared for their young. He is one of the best-known paleontologists in the United States...
has identified fragmentary lambeosaurine jaws from the Bearpaw Formation
Bearpaw Formation
The Bearpaw Formation, also called the Bearpaw Shale, is a sedimentary rock formation found in northwestern North America. It is exposed in the U.S. state of Montana, as well as the Canadian provinces of Alberta and Saskatchewan, east of the Rocky Mountains...
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,...
as possibly belonging to L. magnicristatus; these represent the first lambeosaurine remains from marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
rocks. The large "L." laticaudus (Morris, 1981), known from disassociated remains from several individuals, is accepted as a potential species as well, although it could instead be a species of Hypacrosaurus. Its validity has been questioned by the describers of Velafrons
Velafrons
Velafrons is a genus of lambeosaurine hadrosaurid dinosaur from the Late Cretaceous of Mexico. It is known from a mostly complete skull and partial skeleton of a juvenile individual, with a bony crest on the forehead...
, who find its remains to be nondiagnostic but distinct from their genus. The specific name here is derived from the Latin latus "broad" and cauda "tail".
L. paucidens (Marsh, 1889) is regarded as a dubious name
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
and is listed as Hadrosaurus paucidens in the latest review, although at least one author, Donald F. Glut
Donald F. Glut
Donald F. Glut is an American writer, motion picture director, screenwriter, amateur paleontologist, musician and actor....
, accepts it as a species of Lambeosaurus. In this case, the specific epithet is derived from the Latin pauci- "few" and dens "tooth". The irregularities of Procheneosaurus cranibrevis, and the identity of the type as a juvenile lambeosaur, were recognized in 2005, and thus have not yet entered wide circulation. Finally, Didanodon and Trachodon altidens have received confusing treatment in the most recent review: Didanodon was assigned without comment to Lambeosaurus, yet the species Trachodon altidens was listed separately in a table of dubious names.
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...
, were members 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 that included such well-known dinosaurs 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....
, Styracosaurus
Styracosaurus
Styracosaurus was a genus of herbivorous ceratopsian dinosaur from the Cretaceous Period , about 76.5 to 75.0 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 Prosaurolophus
Prosaurolophus
Prosaurolophus is a genus of hadrosaurid dinosaur from the Late Cretaceous of North America. It is known from the remains of at least 25 individuals belonging to two species, including skulls and skeletons, but it remains obscure...
, 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...
, Corythosaurus, and Parasaurolophus
Parasaurolophus
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 , P. tubicen, and the...
, 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
Ankylosauria
Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. They are first known to have appeared in the early Jurassic Period of...
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:...
and 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...
. 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. The anatomically similar L. lambei, L. magnicristatus, and Corythosaurus were separated by time within the formation, based on stratigraphy
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
. Corythosaurus fossils are known from the lower two-thirds of the Formation, L. lambei fossils are present in the upper third, and L. magnicristatus remains are rare and present only at the very top, where the marine influence was greater.
Feeding
Plant
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 mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
ian 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 replaced and were packed into dental batteries that each contained over 100 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. Feeding would have been from the ground up to around 4 meters (13 ft) above. 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 Lambeosaurus and its relatives could feed more selectively than their broad-beaked, crestless counterparts.
Cranial crest
Like other lambeosaurinesLambeosaurinae
Lambeosaurinae 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...
such as Parasaurolophus and Corythosaurus, Lambeosaurus had a distinctive crest on the top of its head. Its nasal cavity ran back through this crest, making it mostly hollow. Many suggestions have been made for the function or functions of the crest, including housing 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, improving the 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...
, use as a snorkel or air trap, acting as a resonating chamber for making sounds, or being a method for different species or different sexes of the same species to recognize each other. Social functions such as noisemaking and recognition have become the most widely accepted of the various hypotheses.
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
Diurnal animal
Diurnality is a plant or animal behavior characterized by activity during the day and sleeping at night.-In animals:Animals that are not diurnal might be nocturnal or crepuscular . Many animal species are diurnal, including many mammals, insects, reptiles and birds...
habits, evidence that sight was important to these animals. The hadrosaurid sense of hearing
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...
also appears to be strong. 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...
, and 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. This indicates 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. If used as a noisemaker, the crest could also have provided recognizable differences for different species or sexes, because the differing layouts of the nasal passages corresponding to the different crest shapes would have produced intrinsically different sounds.
External links
- Lambeosaurus Paleobiology Database (technical)
- Lambeosaurus Natural History Museum
- Lambeosaurinae at Thescelosaurus!