Edmontosaurus annectens
Encyclopedia
Edmontosaurus annectens is a species
of flat-headed or saurolophine hadrosaurid
ornithopod
dinosaur
(a "duck-billed dinosaur") from the very end of the Cretaceous
Period, in what is now North America
. Remains of E. annectens have been preserved in the Frenchman
, Hell Creek
, and Lance Formation
s. All of these formations are dated to the late Maastrichtian
stage of the Late Cretaceous
Period, representing the last three million years before the extinction of the dinosaurs
(68 to 65 million years ago). Edmontosaurus annectens is known from numerous specimens, including at least twenty partial to complete skulls, discovered in the U.S. states of Montana
, South Dakota
and Wyoming
, and the Canadian
province of Saskatchewan
. It was a large animal, up to approximately 12 metres (39.4 ft) in length, with an extremely long and low skull
. E. annectens exhibits one of the most striking examples of the "duckbill" snout common to hadrosaurs. It has a long taxonomic history that includes the genera Anatosaurus, Anatotitan
, Claosaurus
, Diclonius
, Thespesius
, and Trachodon
.
The skull and skeleton of E. annectens are well-known. Edward Drinker Cope
estimated the length of one specimen as about 38 feet (11.6 m) long, with a skull 3.87 feet (1.2 m) long. This body length estimate was later revised down to a length of 29 feet (8.8 m), although to be fair to Cope a dozen vertebrae, the hips
, and thigh bones
had been carried away by a stream cutting through the skeleton , and the tip of the tail was incomplete. A second skeleton currently exhibited next to Cope's specimen, but in a standing posture, is estimated at 30 feet (9.1 m) long, with its head 17 feet (5.2 m) above the ground. The hip height of this specimen is estimated as approximately 2.1 metres (6.9 ft). Other sources have estimated the length of E. annectens as approximately 12 metres (39.4 ft). Most specimens are somewhat shorter, representing individuals that are not fully grown. Two well-known mounted skeletons, USNM
2414 and YPM 2182, measure 8 metres (26.2 ft) long and 8.92 metres (29.3 ft) long, respectively. E. annectens may have weighed about 3 metric tons (3.3 tons
).
The skull of E. annectens is known for its long, wide muzzle. Cope compared this feature to that of a goose
in side view, and to a short-billed spoonbill in top view. The skull was longer and lower proportionally than in any other known hadrosaurid. The toothless portion of the anterior
mandible
was relatively longer than in any hadrosaur. The extreme length and breadth did not appear until an individual reached maturity, so many specimens lack the distinctive shape. The bones surrounding the large openings for the nostril
s formed deep pockets around the openings. The eye sockets
were rectangular and longer front to back than top to bottom, although this may have been exaggerated by postmortem crushing. The skull roof was flat and lacked a bony crest, and the quadrate bone
that formed the articulation with the lower jaw was distinctly curved. The lower jaw was long and straight, lacking the downward curve seen in other hadrosaurids, and possessing a heavy ridge running its length. The predentary
was wide and shovel-like. The ridge on the lower jaw may have reinforced the long, slender structure.
As mounted, the vertebral column of E. annectens includes twelve neck, twelve back, nine sacral
, and at least thirty tail vertebrae. The limb bones were longer and more lightly built than those of other hadrosaurids of comparable size. E. annectens had a distinctive pelvis, based on the proportions and form of the pubis bone. E. annectens, like other hadrosaurids, could move both on two legs and on four legs
. It probably preferred to forage for food on four legs, but ran on two. Henry Fairfield Osborn
used the skeletons in the American Museum of Natural History
to portray both quadrupedal and bipedal stances for E. annectens.
in 1902, to Jack Horner
, David B. Weishampel, and Catherine Forster in 2004, and most recently Nicolás Campione and David Evans, have proposed that the large, flat-headed specimens most recently classified as Anatotitan copei belong to E. annectens.
E. annectens was also historically classified in an independent genus, Anatosaurus, following the influential 1942 revision of Hadrosauridae by Richard Swann Lull
and Nelda Wright, until it was reclassified as a species of Edmontosaurus by Michael K. Brett-Surman. With the discovery that A. copei and E. annectens likely represent the same species, some paleontologists have proposed using Anatosaurus as a valid genus name for E. annectens.
E. annectens has a complicated taxonomic
history, with various specimens having been classified in a variety of genera. Its history involves Anatosaurus, Anatotitan, Claosaurus
, Diclonius
, Hadrosaurus
, Thespesius
, and Trachodon
, as well as Edmontosaurus. References predating the 1980s typically use Anatosaurus, Claosaurus, Diclonius, Thespesius, or Trachodon for E. annectens fossils, depending on author and date.
(specimen on which a taxonomic name is based) of Anatosaurus copei (Anatotitan), was a complete skull and most of a skeleton collected in 1882 by Dr. J. L. Wortman and R. S. Hill for famous American paleontologist Edward Drinker Cope
. This specimen, found in Hell Creek Formation
rocks, came from northeast of the Black Hills
of South Dakota
and originally had extensive skin impressions. It was missing most of the pelvis and part of the torso due to a stream cutting through it. The bill had impressions of a horny
sheath with a tooth-like series of interlocking points on the upper and lower jaws. When describing this specimen AMNH
5730, Cope assigned it to Diclonius mirabilis
. This combination was created by combining Diclonius, a hadrosaurid genus Cope had named earlier from teeth, with Trachodon mirabilis
, an older name based on teeth and published by Joseph Leidy
. Cope believed that Leidy had abandoned Trachodon, so he assigned the old species to his genus. Leidy had come to recognize that his Trachodon was based on the remains of multiple kinds of dinosaurs, and had made some attempts to revise the genus, but had not made a formal declaration of his intentions.
Cope's description promoted hadrosaurids as amphibious, contributing to this long-time image. His reasoning was that the teeth of the lower jaw were weakly connected to the bone and liable to break off if used to consume terrestrial food, and he described the beak as weak as well. Unfortunately for Cope, aside from misidentifying several of the skull bones, by chance the lower jaws were missing the walls supporting the teeth from the inside; the teeth were actually well-supported. Cope intended to describe the skeleton as well as the skull, but his promised paper never appeared. It was purchased for the American Museum of Natural History in 1899, where it acquired its present designation AMNH 5730.
Several years after Cope's description, his rival Othniel Charles Marsh
published on a sizable lower jaw recovered by John Bell Hatcher in 1889 from Lance Formation
rocks in Niobrara County, Wyoming
. Marsh named this partial jaw Trachodon longiceps. It is cataloged as YPM 616. As noted by Lull and Wright, this long slender partial jaw shares with Cope's specimen a prominent ridge running on its side. However, it is much larger: Cope's specimen had a dentary, or tooth-bearing bone of the lower jaw, that is 92 centimetres (36.2 in) long, whereas Marsh's dentary is estimated at 110 centimetres (43.3 in) long.
A second mostly complete skeleton (AMNH 5886) was found in 1904 in Hell Creek Formation rocks at Crooked Creek in central Montana
by Oscar Hunter, a rancher. Upon finding the partially-exposed specimen, he and a companion argued about whether or not the remains were recent or fossil. Hunter demonstrated that they were brittle and thus stone by kicking the tops off the vertebrae, an act later lamented by the eventual collector Barnum Brown
. Another cowboy, Alfred Sensiba, bought the specimen from Hunter for a pistol
, and later sold it to Brown, who excavated it for the American Museum of Natural History in 1906. This specimen had a nearly complete vertebral column, permitting the restoration of Cope's specimen. In 1907, these two specimens were famously mounted side-by-side in the American Museum of Natural History, under the name Trachodon mirabilis. Cope's specimen is positioned on all fours with its head down, as if feeding, because it has the better skull, while Brown's specimen, with a less perfect skull, is posed bipedally with the head less accessible. Henry Fairfield Osborn
described the tableau as representing the two animals feeding along a marsh
, the standing individual having been startled by the approach of a Tyrannosaurus
. Impressions of appropriate plant remains and shells based on associated fossils were included on the base of the group, including ginkgo
leaves, Sequoia
cones, and horsetail rushes.
The species now known as Edmontosaurus annectens was named in 1892 as Claosaurus annectens by Othniel Charles Marsh
. This species is based on
USNM
2414, a partial skull-roof and skeleton, with a second skull and skeleton, YPM 2182, designated the paratype
. Both were collected in 1891 by John Bell Hatcher
from the late Maastrichtian-age Upper Cretaceous Lance Formation
of Niobrara County (then part of Converse County), Wyoming
. This species has some historical footnotes attached: it is among the first dinosaurs to receive a skeletal restoration, and is the first hadrosaurid so restored; and YPM 2182 and UNSM 2414 are, respectively, the first and second essentially complete mounted dinosaur skeletons in the United States. YPM 2182 was put on display in 1901, and USNM 2414 in 1904.
In the first decade of the twentieth century, two additional important specimens of C. annectens were recovered. The first, the "Trachodon mummy
" (AMNH 5060), was discovered in 1908 by Charles Hazelius Sternberg
and his sons in Lance Formation rocks near Lusk
, Wyoming. Sternberg was working for the British Museum of Natural History
, but Henry Fairfield Osborn
of the American Museum of Natural History was able to purchase the specimen for $2,000. The Sternbergs recovered a second similar specimen from the same area in 1910, not as well-preserved but also found with skin impressions. They sold this specimen (SM 4036) to the Senckenberg Museum
in Germany
.
Edmontosaurus itself was coined in 1917 by Lawrence Lambe
for two partial skeletons found in the Horseshoe Canyon Formation
(formerly the lower Edmonton Formation) along the Red Deer River
of southern Alberta, Canada. The Horseshoe Canyon Formation is older than the rocks in which Claosaurus annectens was found. Lambe found that his new dinosaur compared best to Cope's Diclonius mirabilis.
In 1926, Charles Mortram Sternberg
named Thespesius saskatchewanensis for NMC
8509, a skull and partial skeleton from the Wood Mountain
plateau of southern Saskatchewan
. He had collected this specimen in 1921, from rocks that were assigned to the Lance Formation, now the Frenchman Formation
. NMC 8509 included an almost complete skull, numerous vertebrae, partial shoulder and hip girdles, and partial hind limbs, representing the first substantial dinosaur specimen recovered from Saskatchewan. Sternberg opted to assign it to Thespesius because that was the only hadrosaurid genus known from the Lance Formation at the time. At the time, T. saskatchewanensis was unusual because of its small size, estimated at 7 to 7.3 m (23 to 24 ft) in length.
-like" Claosaurus annectens and the "duck-billed" Hadrosaurus (based on Cope's Diclonius mirabilis), while Hatcher explicitly identified C. annectens as synonymous with the hadrosaurid represented by those same duck-billed skulls, the two differentiated only by individual variation or distortion from pressure. Hatcher's revision, published in 1902, was sweeping: he considered almost all hadrosaurid genera then known as synonyms of Trachodon. This included Cionodon
, Diclonius, Hadrosaurus, Ornithotarsus
, Pteropelyx
, and Thespesius, as well as Claorhynchus
and Polyonax
, fragmentary genera now thought to be horned dinosaurs
. Hatcher's work led to a brief consensus until about 1910, when new material from Canada and Montana showed a greater diversity of hadrosaurids than previously suspected. Charles W. Gilmore
in 1915 reassessed hadrosaurids and recommended that Thespesius be reintroduced for hadrosaurids from the Lance Formation and rock units of equivalent age, and that Trachodon, based on inadequate material, should be restricted to a hadrosaurid from the older Judith River Formation
and its equivalents. In regards to Claosaurus annectens, he recommended that it be considered the same as Thespesius occidentalis. A multiplicity of names resumed, with the American Museum duckbills being known as Diclonius mirabilis, Trachodon mirabilis, Trachodon annectens, Claosaurus, or Thespesius.
on hadrosaurian dinosaurs of North America, they opted to settle the questions revolving around the American Museum duckbills, Marsh's Claosaurus annectens, and several other species by creating a new generic name. They created the new genus Anatosaurus ("duck lizard", because of its wide, duck-like beak; Latin
anas = duck + Greek
sauros = lizard) and made Marsh's species the type species
, calling it Anatosaurus annectens. To this genus, they also assigned Marsh's Trachodon longiceps, a pair of species that had been assigned to Thespesius under Gilmore's "Lance Formation hadrosaurid" conception (T. edmontoni from Gilmore in 1924 and T. saskatchewanensis), and Cope's Diclonius mirabilis. Lull and Wright decided to remove the American Museum specimens from Diclonius (or Trachodon) because they found no convincing reason to assign the specimens to either. Because this left the skeletons without a species name, Lull and Wright gave them their own species, Anatosaurus copei, in honor of Cope. Cope's original specimen (AMNH 5730) was made the holotype
of the species, with Brown's (AMNH 5886) as the plesiotype. Anatosaurus would come to be called the "classic duck-billed dinosaur."
This state of affairs persisted for several decades, until Michael K. Brett-Surman reexamined the pertinent material for his graduate studies in the 1970s and 1980s. He concluded that the type species of Anatosaurus, A. annectens, was actually a species of Edmontosaurus, and that A. copei was different enough to warrant its own genus. Although theses and dissertations are not regarded as official publications by the International Commission on Zoological Nomenclature
, which regulates the naming of organisms, his conclusions were known to other paleontologists, and were adopted by several popular works of the time. His replacement name, Anatotitan (Latin
anas ("duck") and the Greek
Titan
, meaning large), was known and published as such in the popular literature by 1990. Formal publication of the name Anatotitan copei took place the same year, in an article co-written by Brett-Surman with Ralph Chapman
(although the name is sometimes credited as Brett-Surman vide Chapman and Brett-Surman because it came out of Brett-Surman's work). Of the remaining species of Anatosaurus, A. saskatchewanensis and A. edmontoni were assigned to Edmontosaurus as well, and A. longiceps went to Anatotitan, as either a second species or as a synonym of A. copei. It may be a synonym of E. annectens. Because the type species of Anatosaurus (A. annectens) was sunk into Edmontosaurus, the name Anatosaurus is abandoned as a junior synonym
of Edmontosaurus.
The conception of Edmontosaurus that emerged included three valid species: the type E. regalis, E. annectens (including Anatosaurus edmontoni, emended to edmontonensis), and E. saskatchewanensis. The debate about the proper taxonomy of the A. copei specimens continues to the present: returning to Hatcher's argument of 1902, Jack Horner, David B. Weishampel, and Catherine Forster regarded Anatotitan copei as representing specimens of Edmontosaurus annectens with crushed skulls. In 2007 another "mummy" was announced; nicknamed "Dakota
", it was discovered in 1999 by Tyler Lyson
, and came from the Hell Creek Formation
of North Dakota
.
In a 2011 study by Nicolás Campione and David Evans, the authors conducted the first-ever morphometric analysis of the various specimens assigned to Edmontosaurus. They concluded that only two species are valid: E. regalis, from the late Campanian, and E. annectens, from the late Maastrichtian. Their study provided further evidence that Anatotitan copei is a synonym of E. annectens; specifically, that the long, low skull of A. copei is the result of ontogenetic change and represents mature E. annectens individuals. E. saskatechwanensis represents young E. annectens, and Anatosaurus edmontoni specimens belong to E. regalis, not E. annectens. The reassessment of Edmontosaurus assigns twenty skulls to E. annectens. Adult skulls can be distinguished from skulls of E. regalis by the elongate snout and other details of skull anatomy.
-age rocks of the Hell Creek
and Lance Formation
s from South Dakota, Montana, and Wyoming, USA and the Frenchman Formation
of Saskatchewan, Canada.
The Lancian time interval was the last interval before the Cretaceous–Tertiary extinction event that eliminated non-avian
dinosaurs. Edmontosaurus was one of the more common dinosaurs of the interval. Robert Bakker reports that it made up one-seventh of the large dinosaur sample, with most of the rest (five-sixths) made up of the horned dinosaur Triceratops
. The coastal plain
Triceratops–Edmontosaurus association, dominated by Triceratops, extended from Colorado to Saskatchewan. Typical dinosaur faunas of the Lancian formations where Edmontosaurus annectens has been found also included the hypsilophodont Thescelosaurus
, the rare ceratopsid Torosaurus
, the pachycephalosaurid Pachycephalosaurus
, the ankylosaurid Ankylosaurus
, and the theropods Ornithomimus
, Troodon
, and Tyrannosaurus
.
The Hell Creek Formation, as typified by exposures in the Fort Peck
area of Montana, has been interpreted as a flat forested floodplain, with a relatively dry subtropical
climate that supported a variety of plants ranging from angiosperm
tree
s, to conifers such as bald cypress, to fern
s and ginkgo
s. The coastline was hundreds of kilometers or miles to the east. Stream-dwelling turtles and tree-dwelling multituberculate
mammals were diverse, and monitor lizard
s as large as the modern Komodo dragon
hunted on the ground. Triceratops was the most abundant large dinosaur, and Thescelosaurus the most abundant small herbivorous dinosaur. Edmontosaur remains have been collected here from stream channel sands, and include fossils from individuals as young as a meter- or yard-long infant. The edmontosaur fossils probably represent accumulations from groups on the move.
The Lance Formation, as typified by exposures approximately 100 kilometres (62.1 mi) north of Fort Laramie
in eastern Wyoming, has been interpreted as a bayou
setting similar to the Louisiana
coastal plain. It was closer to a large delta than the Hell Creek Formation depositional setting to the north and received much more sediment. Tropical araucarian
conifers
and palm
trees dotted the hardwood
forests, differentiating the flora from the northern coastal plain. The climate was humid and subtropical, with conifers, palmettos
, and ferns in the swamps, and conifers, ash, live oak
, and shrub
s in the forests. Freshwater fish, salamanders, turtles, diverse lizards, snakes, shorebirds, and small mammals lived alongside the dinosaurs. Small dinosaurs are not known in as great of abundance here as in the Hell Creek rocks, but Thescelosaurus once again seems to have been relatively common. Triceratops is known from many skulls, which tend to be somewhat smaller than those of more northern individuals. The Lance Formation is the setting of two edmontosaur "mummies".
s, eating plant
s with a sophisticated skull that permitted a grinding motion analogous to chewing
. Their teeth
were continually replaced and packed into dental batteries that contained hundreds of teeth, only a relative handful of which were in use at any time. Plant material would have been cropped by the broad beak, and held in the jaws by a cheek
-like structure. Feeding would have been from the ground up to around 4 meters (13 ft) above. Like other hadrosaurs, they could have moved both bipedally and quadruped
ally.
The extensive depressions surrounding its nasal openings
may hosted nasal diverticula. These postulated diverticula
would have taken the form of inflatable soft-tissue sacs. Such sacs could be used for both visual and auditory signals.
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...
of flat-headed or saurolophine 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...
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...
(a "duck-billed dinosaur") from the very end of the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Period, 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...
. Remains of E. annectens have been preserved in the Frenchman
Frenchman Formation
The Frenchman Formation is a division of Upper Cretaceous rocks found in Saskatchewan, Canada. More accurately described as Late Maastrichtian, these rocks contain the youngest of dinosaur genera, much like the Hell Creek Formation in the United States....
, Hell Creek
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...
, and Lance Formation
Lance Formation
The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas...
s. All of these formations are dated to the 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...
stage of 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, representing the last three million years before the extinction of the dinosaurs
K–T boundary
The K–T boundary is a geological signature, usually a thin band, dated to 65.5 ± 0.3 Ma ago. K is the traditional abbreviation for the Cretaceous period, and T is the abbreviation for the Tertiary period...
(68 to 65 million years ago). Edmontosaurus annectens is known from numerous specimens, including at least twenty partial to complete skulls, discovered in the U.S. states 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,...
, South Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...
and Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
, and the Canadian
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...
province of Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
. It was a large animal, up to approximately 12 metres (39.4 ft) in length, with an extremely long and low 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...
. E. annectens exhibits one of the most striking examples of the "duckbill" snout common to hadrosaurs. It has a long taxonomic history that includes the genera Anatosaurus, Anatotitan
Anatotitan
Anatotitan is a genus of flat-headed or hadrosaurine hadrosaurid ornithopod dinosaur from the very end of the Cretaceous Period, in what is now North America...
, Claosaurus
Claosaurus
Claosaurus is a genus of primitive hadrosaurid that lived during the Late Cretaceous Period .Evidence of its existence was first found near the Smoky Hill River in Kansas, USA in the form of partial skull fragments and as an articulated postcranial skeleton...
, Diclonius
Diclonius
Diclonius is a genus of dinosaur from the Late Cretaceous. It was a hadrosaur based solely on teeth. Its fossils have been found in North America. The name is in reference to the method of tooth replacement, in which newly erupting replacement teeth could be in functional use at the same time as...
, Thespesius
Thespesius
Thespesius is a dubious genus of hadrosaurid dinosaur from the late Maastrichtian-age Upper Cretaceous Lance Formation of South Dakota....
, and Trachodon
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...
.
Description
Edward Drinker Cope
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
estimated the length of one specimen as about 38 feet (11.6 m) long, with a skull 3.87 feet (1.2 m) long. This body length estimate was later revised down to a length of 29 feet (8.8 m), although to be fair to Cope a dozen vertebrae, the hips
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:...
, and thigh bones
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...
had been carried away by a stream cutting through the skeleton , and the tip of the tail was incomplete. A second skeleton currently exhibited next to Cope's specimen, but in a standing posture, is estimated at 30 feet (9.1 m) long, with its head 17 feet (5.2 m) above the ground. The hip height of this specimen is estimated as approximately 2.1 metres (6.9 ft). Other sources have estimated the length of E. annectens as approximately 12 metres (39.4 ft). Most specimens are somewhat shorter, representing individuals that are not fully grown. Two well-known mounted skeletons, 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....
2414 and YPM 2182, measure 8 metres (26.2 ft) long and 8.92 metres (29.3 ft) long, respectively. E. annectens may have weighed about 3 metric tons (3.3 tons
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...
).
The skull of E. annectens is known for its long, wide muzzle. Cope compared this feature to that of a goose
Goose
The word goose is the English name for a group of waterfowl, belonging to the family Anatidae. This family also includes swans, most of which are larger than true geese, and ducks, which are smaller....
in side view, and to a short-billed spoonbill in top view. The skull was longer and lower proportionally than in any other known hadrosaurid. The toothless portion of the anterior
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
was relatively longer than in any hadrosaur. The extreme length and breadth did not appear until an individual reached maturity, so many specimens lack the distinctive shape. The bones surrounding the large openings for the nostril
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s formed deep pockets around the openings. The 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...
were rectangular and longer front to back than top to bottom, although this may have been exaggerated by postmortem crushing. The skull roof was flat and lacked a bony crest, and the quadrate bone
Quadrate bone
The quadrate bone is part of a skull in most tetrapods, including amphibians, sauropsids , and early synapsids. In these animals it connects to the quadratojugal and squamosal in the skull, and forms part of the jaw joint .- Evolutionary variation :In snakes, the quadrate bone has become elongated...
that formed the articulation with the lower jaw was distinctly curved. The lower jaw was long and straight, lacking the downward curve seen in other hadrosaurids, and possessing a heavy ridge running its length. The predentary
Predentary
The predentary is an 'extra' bone in the front of the lower jaw, which extended the dentary . It is found in the fossilised remains of ornithischian dinosaurs, which were herbivorous. The predentary coincided with the premaxilla in the upper jaw. Together they formed a beak-like apparatus used to...
was wide and shovel-like. The ridge on the lower jaw may have reinforced the long, slender structure.
As mounted, the vertebral column of E. annectens includes twelve neck, twelve back, nine sacral
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
, and at least thirty tail vertebrae. The limb bones were longer and more lightly built than those of other hadrosaurids of comparable size. E. annectens had a distinctive pelvis, based on the proportions and form of the pubis bone. E. annectens, like other hadrosaurids, could move both on two legs and on four legs
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"...
. It probably preferred to forage for food on four legs, but ran on two. Henry Fairfield Osborn
Henry Fairfield Osborn
Henry Fairfield Osborn, Sr. ForMemRS was an American geologist, paleontologist, and eugenicist.-Early life and career:...
used the skeletons in 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...
to portray both quadrupedal and bipedal stances for E. annectens.
Classification
E. annectens was a saurolophine or "flat-headed" hadrosaurid; this group was historically known as Hadrosaurinae. Species now considered to be synonyms of Edmontosaurus annectens were long recognized as closely related to both the genus and the species. However, the skull of the sub-adult type specimen of E. annectens differs noticeably from fully mature remains, so many researchers had classified the two growth stages as different species or even genera. On the other side of the issue, other authors, from John Bell HatcherJohn Bell Hatcher
John Bell Hatcher was an American paleontologist and fossil hunter best known for discovering Torosaurus.-Biography:...
in 1902, to 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...
, David B. Weishampel, and Catherine Forster in 2004, and most recently Nicolás Campione and David Evans, have proposed that the large, flat-headed specimens most recently classified as Anatotitan copei belong to E. annectens.
E. annectens was also historically classified in an independent genus, Anatosaurus, following the influential 1942 revision of Hadrosauridae by Richard Swann Lull
R. S. Lull
Richard Swann Lull was an American paleontologist from the early 20th century, active at Yale University, who is largely remembered now for championing a Pre-Neo-Darwinian Synthesis view of evolution, whereby mutation could unlock mysterious genetic drives that, over time, would lead populations...
and Nelda Wright, until it was reclassified as a species of Edmontosaurus by Michael K. Brett-Surman. With the discovery that A. copei and E. annectens likely represent the same species, some paleontologists have proposed using Anatosaurus as a valid genus name for E. annectens.
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, with various specimens having been classified in a variety of genera. Its history involves Anatosaurus, Anatotitan, Claosaurus
Claosaurus
Claosaurus is a genus of primitive hadrosaurid that lived during the Late Cretaceous Period .Evidence of its existence was first found near the Smoky Hill River in Kansas, USA in the form of partial skull fragments and as an articulated postcranial skeleton...
, Diclonius
Diclonius
Diclonius is a genus of dinosaur from the Late Cretaceous. It was a hadrosaur based solely on teeth. Its fossils have been found in North America. The name is in reference to the method of tooth replacement, in which newly erupting replacement teeth could be in functional use at the same time as...
, 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...
, Thespesius
Thespesius
Thespesius is a dubious genus of hadrosaurid dinosaur from the late Maastrichtian-age Upper Cretaceous Lance Formation of South Dakota....
, and Trachodon
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...
, as well as Edmontosaurus. References predating the 1980s typically use Anatosaurus, Claosaurus, Diclonius, Thespesius, or Trachodon for E. annectens fossils, depending on author and date.
Cope's Diclonius mirabilis
The history of E. annectens predates both Edmontosaurus and annectens. The first good specimen, , the former holotypeHolotype
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...
(specimen on which a taxonomic name is based) of Anatosaurus copei (Anatotitan), was a complete skull and most of a skeleton collected in 1882 by Dr. J. L. Wortman and R. S. Hill for famous American paleontologist Edward Drinker Cope
Edward Drinker Cope
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
. This specimen, found in 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...
rocks, came from northeast of the Black Hills
Black Hills
The Black Hills are a small, isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, USA. Set off from the main body of the Rocky Mountains, the region is something of a geological anomaly—accurately described as an "island of...
of South Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...
and originally had extensive skin impressions. It was missing most of the pelvis and part of the torso due to a stream cutting through it. The bill had impressions of a horny
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...
sheath with a tooth-like series of interlocking points on the upper and lower jaws. When describing this specimen 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...
5730, Cope assigned it to Diclonius mirabilis
Diclonius
Diclonius is a genus of dinosaur from the Late Cretaceous. It was a hadrosaur based solely on teeth. Its fossils have been found in North America. The name is in reference to the method of tooth replacement, in which newly erupting replacement teeth could be in functional use at the same time as...
. This combination was created by combining Diclonius, a hadrosaurid genus Cope had named earlier from teeth, with Trachodon mirabilis
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...
, an older name based on teeth and published by Joseph Leidy
Joseph Leidy
Joseph Leidy was an American paleontologist.Leidy was professor of anatomy at the University of Pennsylvania, and later was a professor of natural history at Swarthmore College. His book Extinct Fauna of Dakota and Nebraska contained many species not previously described and many previously...
. Cope believed that Leidy had abandoned Trachodon, so he assigned the old species to his genus. Leidy had come to recognize that his Trachodon was based on the remains of multiple kinds of dinosaurs, and had made some attempts to revise the genus, but had not made a formal declaration of his intentions.
Cope's description promoted hadrosaurids as amphibious, contributing to this long-time image. His reasoning was that the teeth of the lower jaw were weakly connected to the bone and liable to break off if used to consume terrestrial food, and he described the beak as weak as well. Unfortunately for Cope, aside from misidentifying several of the skull bones, by chance the lower jaws were missing the walls supporting the teeth from the inside; the teeth were actually well-supported. Cope intended to describe the skeleton as well as the skull, but his promised paper never appeared. It was purchased for the American Museum of Natural History in 1899, where it acquired its present designation AMNH 5730.
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...
published on a sizable lower jaw recovered by John Bell Hatcher in 1889 from Lance Formation
Lance Formation
The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas...
rocks in Niobrara County, Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
. Marsh named this partial jaw Trachodon longiceps. It is cataloged as YPM 616. As noted by Lull and Wright, this long slender partial jaw shares with Cope's specimen a prominent ridge running on its side. However, it is much larger: Cope's specimen had a dentary, or tooth-bearing bone of the lower jaw, that is 92 centimetres (36.2 in) long, whereas Marsh's dentary is estimated at 110 centimetres (43.3 in) long.
A second mostly complete skeleton (AMNH 5886) was found in 1904 in Hell Creek Formation rocks at Crooked Creek in central 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,...
by Oscar Hunter, a rancher. Upon finding the partially-exposed specimen, he and a companion argued about whether or not the remains were recent or fossil. Hunter demonstrated that they were brittle and thus stone by kicking the tops off the vertebrae, an act later lamented by the eventual collector Barnum Brown
Barnum Brown
Barnum Brown , a paleontologist born in Carbondale, Kansas, and named after the circus showman P.T. Barnum, discovered the second fossil of Tyrannosaurus rex during a career that made him one of the most famous fossil hunters working from the late Victorian era into the early 20th century.Sponsored...
. Another cowboy, Alfred Sensiba, bought the specimen from Hunter for a pistol
Pistol
When distinguished as a subset of handguns, a pistol is a handgun with a chamber that is integral with the barrel, as opposed to a revolver, wherein the chamber is separate from the barrel as a revolving cylinder. Typically, pistols have an effective range of about 100 feet.-History:The pistol...
, and later sold it to Brown, who excavated it for the American Museum of Natural History in 1906. This specimen had a nearly complete vertebral column, permitting the restoration of Cope's specimen. In 1907, these two specimens were famously mounted side-by-side in the American Museum of Natural History, under the name Trachodon mirabilis. Cope's specimen is positioned on all fours with its head down, as if feeding, because it has the better skull, while Brown's specimen, with a less perfect skull, is posed bipedally with the head less accessible. Henry Fairfield Osborn
Henry Fairfield Osborn
Henry Fairfield Osborn, Sr. ForMemRS was an American geologist, paleontologist, and eugenicist.-Early life and career:...
described the tableau as representing the two animals feeding along a marsh
Marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
, the standing individual having been startled by the approach of a Tyrannosaurus
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...
. Impressions of appropriate plant remains and shells based on associated fossils were included on the base of the group, including ginkgo
Ginkgo
Ginkgo , also spelled gingko and known as the Maidenhair Tree, is a unique species of tree with no close living relatives...
leaves, Sequoia
Sequoioideae
Sequoioideae is a subfamily in the Cupressaceae family, with three genera.-Genera:The three redwood subfamily genera are: Sequoia and Sequoiadendron of California and Oregon, USA; and Metasequoia in China. The redwood species contains the largest and tallest trees in the world. These trees can live...
cones, and horsetail rushes.
Marsh's Claosaurus annectens
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...
. This species 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...
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....
2414, a partial skull-roof and skeleton, with a second skull and skeleton, YPM 2182, designated the paratype
Paratype
Paratype is a technical term used in the scientific naming of species and other taxa of organisms. The exact meaning of the term paratype when it is used in zoology is not the same as the meaning when it is used in botany...
. Both were collected in 1891 by John Bell Hatcher
John Bell Hatcher
John Bell Hatcher was an American paleontologist and fossil hunter best known for discovering Torosaurus.-Biography:...
from the late Maastrichtian-age Upper Cretaceous Lance Formation
Lance Formation
The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas...
of Niobrara County (then part of Converse County), Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
. This species has some historical footnotes attached: it is among the first dinosaurs to receive a skeletal restoration, and is the first hadrosaurid so restored; and YPM 2182 and UNSM 2414 are, respectively, the first and second essentially complete mounted dinosaur skeletons in the United States. YPM 2182 was put on display in 1901, and USNM 2414 in 1904.
In the first decade of the twentieth century, two additional important specimens of C. annectens were recovered. The first, the "Trachodon mummy
Trachodon mummy
The Trachodon mummy is a very well preserved fossil of Edmontosaurus annectens, a duckbilled dinosaur. It was found by Charles Hazelius Sternberg and his three sons near Lusk, Wyoming, USA in 1908...
" (AMNH 5060), was discovered in 1908 by Charles Hazelius 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...
and his sons in Lance Formation rocks near Lusk
Lusk, Wyoming
Lusk is a town in Niobrara County, Wyoming, United States. The population was 1,447 at the 2000 census. It is the county seat of Niobrara County. The town was laid out in June 1886 by engineers working on the Wyoming Central Railway. It was named after Frank S...
, Wyoming. Sternberg was working for the British Museum of Natural History
Natural History Museum
The Natural History Museum is one of three large museums on Exhibition Road, South Kensington, London, England . Its main frontage is on Cromwell Road...
, but Henry Fairfield Osborn
Henry Fairfield Osborn
Henry Fairfield Osborn, Sr. ForMemRS was an American geologist, paleontologist, and eugenicist.-Early life and career:...
of the American Museum of Natural History was able to purchase the specimen for $2,000. The Sternbergs recovered a second similar specimen from the same area in 1910, not as well-preserved but also found with skin impressions. They sold this specimen (SM 4036) to the Senckenberg Museum
Senckenberg Museum
The Naturmuseum Senckenberg in Frankfurt is the second largest museum of natural history in Germany. It is particularly popular with children, who enjoy the extensive collection of dinosaur skeletons: Senckenberg boasts the largest exhibition of large dinosaurs in Europe. One particular treasure is...
in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
.
Canadian discoveries
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...
for two partial skeletons found in the Horseshoe Canyon Formation
Horseshoe Canyon Formation
The Horseshoe Canyon Formation is part of the Edmonton Group and is up to 230m in thickness. It is Late Campanian to Early Maastrichtian in age and is composed of mudstone, sandstone, and carbonaceous shales...
(formerly the lower Edmonton Formation) 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...
of southern Alberta, Canada. The Horseshoe Canyon Formation is older than the rocks in which Claosaurus annectens was found. Lambe found that his new dinosaur compared best to Cope's Diclonius mirabilis.
In 1926, Charles Mortram 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...
named Thespesius saskatchewanensis for 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...
8509, a skull and partial skeleton from the Wood Mountain
Wood Mountain, Saskatchewan
Wood Mountain is a village in Old Post Rural Municipality 43, Saskatchewan, Canada. The town's name is derived from the Red River Metis word "Monatagne de Bois" , due to the abundance of poplar trees in the otherwise barren region...
plateau of southern Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
. He had collected this specimen in 1921, from rocks that were assigned to the Lance Formation, now the Frenchman Formation
Frenchman Formation
The Frenchman Formation is a division of Upper Cretaceous rocks found in Saskatchewan, Canada. More accurately described as Late Maastrichtian, these rocks contain the youngest of dinosaur genera, much like the Hell Creek Formation in the United States....
. NMC 8509 included an almost complete skull, numerous vertebrae, partial shoulder and hip girdles, and partial hind limbs, representing the first substantial dinosaur specimen recovered from Saskatchewan. Sternberg opted to assign it to Thespesius because that was the only hadrosaurid genus known from the Lance Formation at the time. At the time, T. saskatchewanensis was unusual because of its small size, estimated at 7 to 7.3 m (23 to 24 ft) in length.
Early classifications
Because of the incomplete understanding of hadrosaurids at the time, following Marsh's death in 1897 Claosaurus annectens was variously classified as a species of Claosaurus, Thespesius or Trachodon. Opinions varied greatly; textbooks and encyclopedias drew a distinction between the "IguanodonIguanodon
Iguanodon is a genus of ornithopod dinosaur that lived roughly halfway between the first of the swift bipedal hypsilophodontids and the ornithopods' culmination in the duck-billed dinosaurs...
-like" Claosaurus annectens and the "duck-billed" Hadrosaurus (based on Cope's Diclonius mirabilis), while Hatcher explicitly identified C. annectens as synonymous with the hadrosaurid represented by those same duck-billed skulls, the two differentiated only by individual variation or distortion from pressure. Hatcher's revision, published in 1902, was sweeping: he considered almost all hadrosaurid genera then known as synonyms of Trachodon. This included Cionodon
Cionodon
Cionodon was a genus of dinosaur from the Late Cretaceous Period. The type species, Cionodon arctatus lived in what is now present-day Colorado. It is classified as a hadrosaur, and was formally described by Edward Drinker Cope in 1874. It is a nomen dubium because it is based on very fragmentary...
, Diclonius, Hadrosaurus, Ornithotarsus
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...
, Pteropelyx
Pteropelyx
Pteropelyx is a dubious genus of Late Cretaceous hadrosaurid dinosaur from the Judith River Formation of Montana, named by Edward Drinker Cope in 1889. Historically, several species were assigned to it, all based on extremely fragmentary remains, but there is no evidence to support these assignments...
, and Thespesius, as well as Claorhynchus
Claorhynchus
Claorhynchus is a dubious genus of ornithischian dinosaur with a confusing history behind it...
and Polyonax
Polyonax
Polyonax was a genus of ceratopsid dinosaur from the late Maastrichtian-age Upper Cretaceous Denver Formation of Colorado, USA...
, fragmentary genera now thought to be horned dinosaurs
Ceratopsia
Ceratopsia or Ceratopia is a group of herbivorous, beaked dinosaurs which thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. The earliest known ceratopsian, Yinlong downsi, lived between 161.2 and 155.7...
. Hatcher's work led to a brief consensus until about 1910, when new material from Canada and Montana showed a greater diversity of hadrosaurids than previously suspected. Charles W. Gilmore
Charles W. Gilmore
Charles Whitney Gilmore was an American paleontologist, who named dinosaurs in North America and Mongolia, including the Cretaceous sauropod Alamosaurus, Alectrosaurus, Archaeornithomimus, Bactrosaurus, Brachyceratops, Chirostenotes, Mongolosaurus, Parrosaurus, Pinacosaurus, Styracosaurus and...
in 1915 reassessed hadrosaurids and recommended that Thespesius be reintroduced for hadrosaurids from the Lance Formation and rock units of equivalent age, and that Trachodon, based on inadequate material, should be restricted to a hadrosaurid from the older 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...
and its equivalents. In regards to Claosaurus annectens, he recommended that it be considered the same as Thespesius occidentalis. A multiplicity of names resumed, with the American Museum duckbills being known as Diclonius mirabilis, Trachodon mirabilis, Trachodon annectens, Claosaurus, or Thespesius.
Anatosaurus to the present
This confusing situation was temporarily resolved in 1942 by Richard Swann Lull and Nelda Wright. In their monographMonograph
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 hadrosaurian dinosaurs of North America, they opted to settle the questions revolving around the American Museum duckbills, Marsh's Claosaurus annectens, and several other species by creating a new generic name. They created the new genus Anatosaurus ("duck lizard", because of its wide, duck-like beak; 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...
anas = duck + Greek
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...
sauros = lizard) and made Marsh's species 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...
, calling it Anatosaurus annectens. To this genus, they also assigned Marsh's Trachodon longiceps, a pair of species that had been assigned to Thespesius under Gilmore's "Lance Formation hadrosaurid" conception (T. edmontoni from Gilmore in 1924 and T. saskatchewanensis), and Cope's Diclonius mirabilis. Lull and Wright decided to remove the American Museum specimens from Diclonius (or Trachodon) because they found no convincing reason to assign the specimens to either. Because this left the skeletons without a species name, Lull and Wright gave them their own species, Anatosaurus copei, in honor of Cope. Cope's original specimen (AMNH 5730) was made the holotype
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...
of the species, with Brown's (AMNH 5886) as the plesiotype. Anatosaurus would come to be called the "classic duck-billed dinosaur."
This state of affairs persisted for several decades, until Michael K. Brett-Surman reexamined the pertinent material for his graduate studies in the 1970s and 1980s. He concluded that the type species of Anatosaurus, A. annectens, was actually a species of Edmontosaurus, and that A. copei was different enough to warrant its own genus. Although theses and dissertations are not regarded as official publications by the International Commission on Zoological Nomenclature
International Commission on Zoological Nomenclature
The International Commission on Zoological Nomenclature is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 28 members from 20 countries, mainly practicing zoological taxonomists...
, which regulates the naming of organisms, his conclusions were known to other paleontologists, and were adopted by several popular works of the time. His replacement name, Anatotitan (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...
anas ("duck") and the Greek
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...
Titan
Titan (mythology)
In Greek mythology, the Titans were a race of powerful deities, descendants of Gaia and Uranus, that ruled during the legendary Golden Age....
, meaning large), was known and published as such in the popular literature by 1990. Formal publication of the name Anatotitan copei took place the same year, in an article co-written by Brett-Surman with Ralph Chapman
Ralph Chapman
Ralph D. "Slouie" Chapman was an American football player. He was the son of P.T. Chapman, a wealthy banker in Vienna, Illinois. He played at the guard position for Bob Zuppke's University of Illinois football team from 1912 to 1914. Chapman was selected as the captain of the 1914 Illinois...
(although the name is sometimes credited as Brett-Surman vide Chapman and Brett-Surman because it came out of Brett-Surman's work). Of the remaining species of Anatosaurus, A. saskatchewanensis and A. edmontoni were assigned to Edmontosaurus as well, and A. longiceps went to Anatotitan, as either a second species or as a synonym of A. copei. It may be a synonym of E. annectens. Because the type species of Anatosaurus (A. annectens) was sunk into Edmontosaurus, the name Anatosaurus is abandoned as a junior synonym
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 Edmontosaurus.
The conception of Edmontosaurus that emerged included three valid species: the type E. regalis, E. annectens (including Anatosaurus edmontoni, emended to edmontonensis), and E. saskatchewanensis. The debate about the proper taxonomy of the A. copei specimens continues to the present: returning to Hatcher's argument of 1902, Jack Horner, David B. Weishampel, and Catherine Forster regarded Anatotitan copei as representing specimens of Edmontosaurus annectens with crushed skulls. In 2007 another "mummy" was announced; nicknamed "Dakota
Dakota (fossil)
Dakota is the nickname given to a fossil Edmontosaurus from the Hell Creek Formation in North Dakota. It is about 67 million years old, placing it in the Maastrichtian, the last stage of the Cretaceous period...
", it was discovered in 1999 by Tyler Lyson
Tyler Lyson
Tyler Lyson is the discoverer of the dinosaur fossil Dakota, a fossilized mummified hadrosaur.Lyson received his bachelor's degree in biology from Swarthmore College in 2006, and received a scholarship to study for his PhD in paleontology at Yale University, where he remains as of 2011.In 1999,...
, and came from 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 North Dakota
North Dakota
North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....
.
In a 2011 study by Nicolás Campione and David Evans, the authors conducted the first-ever morphometric analysis of the various specimens assigned to Edmontosaurus. They concluded that only two species are valid: E. regalis, from the late Campanian, and E. annectens, from the late Maastrichtian. Their study provided further evidence that Anatotitan copei is a synonym of E. annectens; specifically, that the long, low skull of A. copei is the result of ontogenetic change and represents mature E. annectens individuals. E. saskatechwanensis represents young E. annectens, and Anatosaurus edmontoni specimens belong to E. regalis, not E. annectens. The reassessment of Edmontosaurus assigns twenty skulls to E. annectens. Adult skulls can be distinguished from skulls of E. regalis by the elongate snout and other details of skull anatomy.
Paleoecology
True E. annectens remains are known only from latest MaastrichtianMaastrichtian
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 rocks of the Hell Creek
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...
and Lance Formation
Lance Formation
The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas...
s from South Dakota, Montana, and Wyoming, USA and the Frenchman Formation
Frenchman Formation
The Frenchman Formation is a division of Upper Cretaceous rocks found in Saskatchewan, Canada. More accurately described as Late Maastrichtian, these rocks contain the youngest of dinosaur genera, much like the Hell Creek Formation in the United States....
of Saskatchewan, Canada.
The Lancian time interval was the last interval before the Cretaceous–Tertiary extinction event that eliminated non-avian
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
dinosaurs. Edmontosaurus was one of the more common dinosaurs of the interval. Robert Bakker reports that it made up one-seventh of the large dinosaur sample, with most of the rest (five-sixths) made up of the horned dinosaur Triceratops
Triceratops
Triceratops is a genus of herbivorous ceratopsid dinosaur which lived during the late Maastrichtian stage of the Late Cretaceous Period, around 68 to 65 million years ago in what is now North America. It was one of the last dinosaur genera to appear before the great Cretaceous–Paleogene...
. The coastal plain
Coastal plain
A coastal plain is an area of flat, low-lying land adjacent to a seacoast and separated from the interior by other features. One of the world's longest coastal plains is located in eastern South America. The southwestern coastal plain of North America is notable for its species diversity...
Triceratops–Edmontosaurus association, dominated by Triceratops, extended from Colorado to Saskatchewan. Typical dinosaur faunas of the Lancian formations where Edmontosaurus annectens has been found also included the hypsilophodont Thescelosaurus
Thescelosaurus
Thescelosaurus was a genus of small ornithopod dinosaur that appeared at the very end of the Late Cretaceous period in North America. It was a member of the last dinosaurian fauna before the Cretaceous-Tertiary extinction event around 65.5 million years ago...
, the rare ceratopsid Torosaurus
Torosaurus
Torosaurus is a genus of ceratopsid dinosaur that lived during the late Cretaceous period , between 70 and 65 million years ago. It possessed one of the largest skulls of any known land animal. The frilled skull reached in length...
, the pachycephalosaurid Pachycephalosaurus
Pachycephalosaurus
Pachycephalosaurus is a genus of pachycephalosaurid dinosaur. It lived during the Late Cretaceous Period of what is now North America. Remains have been excavated in Montana, South Dakota, and Wyoming. It was an herbivorous or omnivorous creature which is only known from a single skull and a few...
, the ankylosaurid Ankylosaurus
Ankylosaurus
Ankylosaurus is a genus of ankylosaurid dinosaur, containing one species, A. magniventris...
, and the theropods 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...
, Troodon
Troodon
Troodon is a genus of relatively small, bird-like dinosaur from the Late Cretaceous period . Discovered in 1855, it was among the first dinosaurs found in North America...
, and Tyrannosaurus
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...
.
Fort Peck, Montana
Fort Peck is a town in Valley County, Montana, United States. The population was 240 at the 2000 census.-History:The name Fort Peck is associated with Col. Campbell K. Peck, the partner of Elias H. Durfee in the Leavenworth, Kansas, trading firm of Durfee and Peck...
area of Montana, has been interpreted as a flat forested floodplain, with a relatively dry subtropical
Subtropics
The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...
climate that supported a variety of plants ranging from angiosperm
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s, to conifers such as bald cypress, to 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 and ginkgo
Ginkgo
Ginkgo , also spelled gingko and known as the Maidenhair Tree, is a unique species of tree with no close living relatives...
s. The coastline was hundreds of kilometers or miles to the east. Stream-dwelling turtles and tree-dwelling multituberculate
Multituberculata
The Multituberculata were a group of rodent-like mammals that existed for approximately one hundred and twenty million years—the longest fossil history of any mammal lineage—but were eventually outcompeted by rodents, becoming extinct during the early Oligocene. At least 200 species are...
mammals were diverse, and monitor lizard
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...
s as large as the modern Komodo dragon
Komodo dragon
The Komodo dragon , also known as the Komodo monitor, is a large species of lizard found in the Indonesian islands of Komodo, Rinca, Flores, Gili Motang and Gili Dasami. A member of the monitor lizard family , it is the largest living species of lizard, growing to a maximum length of in rare cases...
hunted on the ground. Triceratops was the most abundant large dinosaur, and Thescelosaurus the most abundant small herbivorous dinosaur. Edmontosaur remains have been collected here from stream channel sands, and include fossils from individuals as young as a meter- or yard-long infant. The edmontosaur fossils probably represent accumulations from groups on the move.
The Lance Formation, as typified by exposures approximately 100 kilometres (62.1 mi) north of Fort Laramie
Fort Laramie National Historic Site
Fort Laramie was a significant 19th century trading post and diplomatic site located at the confluence of the Laramie River and the North Platte River in the upper Platte River Valley in the eastern part of the U.S. state of Wyoming...
in eastern Wyoming, has been interpreted as a bayou
Bayou
A bayou is an American term for a body of water typically found in flat, low-lying areas, and can refer either to an extremely slow-moving stream or river , or to a marshy lake or wetland. The name "bayou" can also refer to creeks that see level changes due to tides and hold brackish water which...
setting similar to the Louisiana
Louisiana
Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...
coastal plain. It was closer to a large delta than the Hell Creek Formation depositional setting to the north and received much more sediment. Tropical araucarian
Araucariaceae
Araucariaceae, commonly referred to as araucarians, is a very ancient family of coniferous trees. It achieved its maximum diversity in the Jurassic and Cretaceous periods, when it was distributed almost worldwide...
conifers
Pinophyta
The conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 division level taxa within the Kingdom Plantae. Pinophytes are gymnosperms. They are cone-bearing seed plants with vascular tissue; all extant conifers are woody plants, the great majority being...
and palm
Arecaceae
Arecaceae or Palmae , are a family of flowering plants, the only family in the monocot order Arecales. There are roughly 202 currently known genera with around 2600 species, most of which are restricted to tropical, subtropical, and warm temperate climates...
trees dotted the hardwood
Hardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
forests, differentiating the flora from the northern coastal plain. The climate was humid and subtropical, with conifers, palmettos
Sabal
Sabal is a genus of New World palms, many of the species being known as palmetto. They are fan palms , with the leaves with a bare petiole terminating in a rounded fan of numerous leaflets; in some of the species, the leaflets are joined for up to half of their length...
, and ferns in the swamps, and conifers, ash, live oak
Live oak
Live oak , also known as the southern live oak, is a normally evergreen oak tree native to the southeastern United States...
, and shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
s in the forests. Freshwater fish, salamanders, turtles, diverse lizards, snakes, shorebirds, and small mammals lived alongside the dinosaurs. Small dinosaurs are not known in as great of abundance here as in the Hell Creek rocks, but Thescelosaurus once again seems to have been relatively common. Triceratops is known from many skulls, which tend to be somewhat smaller than those of more northern individuals. The Lance Formation is the setting of two edmontosaur "mummies".
Paleobiology
As hadrosaurids, individuals of Edmontosaurus annectens would have been large herbivoreHerbivore
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...
s, eating plant
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 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...
. Their 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 packed into dental batteries that contained hundreds of teeth, only a relative handful of which were in use at any time. Plant material would have been cropped by the broad beak, and 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 structure. Feeding would have been from the ground up to around 4 meters (13 ft) above. Like other hadrosaurs, they could have moved both bipedally and 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"...
ally.
The extensive depressions surrounding its nasal openings
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
may hosted nasal diverticula. These postulated diverticula
Diverticulum
A diverticulum is medical or biological term for an outpouching of a hollow structure in the body. Depending upon which layers of the structure are involved, they are described as being either true or false....
would have taken the form of inflatable soft-tissue sacs. Such sacs could be used for both visual and auditory signals.