Edmontosaurus regalis Temporal range: Late Cretaceous, | |
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Holotype skeleton of Thespesius edmontoni, now thought to be a young E. regalis | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | † Ornithischia |
Clade: | † Ornithopoda |
Family: | † Hadrosauridae |
Subfamily: | † Saurolophinae |
Genus: | † Edmontosaurus |
Species: | †E. regalis |
Binomial name | |
†Edmontosaurus regalis | |
Synonyms | |
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Edmontosaurus regalis is a species of comb-crested hadrosaurid dinosaur. Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian age of the Cretaceous Period 73 million years ago, but it may have possibly lived into the early Maastrichtian. [1]
E. regalis was one of the largest hadrosaurids, measuring up to 12 metres (39 ft) long and weighing around 4.0 metric tons (4.4 short tons). It is classified as a genus of saurolophine (or hadrosaurine) hadrosaurid, a member of the group of hadrosaurids that lacked large, hollow crests, and instead had smaller, solid crests or fleshy combs. [2] The distribution of E. regalis fossils suggests that it preferred coasts and coastal plains. It was a herbivore that could move on both two legs and four. Because it is known from several bone beds, E. regalis is thought to have lived in large groups. The wealth of fossils has allowed researchers to study its paleobiology in detail, including its brain, how it may have fed, and its injuries and pathologies.
Edmontosaurus regalis is known from several fossil specimens. [3] [4] [5] [6] E. regalis was among the largest of hadrosaurids, as a fully grown adult could have been 9 metres (30 ft) long. Some of the larger specimens reached the range of 12 metres (39 ft) [7] to 13 metres (43 ft) long. [8] Its weight was on the order of 4.0 metric tons (4.4 short tons). [9] The type specimen of E. regalis, NMC 2288, is estimated as 9 to 12 metres (30 to 39 ft) long. [10] A 2022 study proposed that E. regalis may have been heavier than its generic relative, E. annectens, but not enough samples exist to provide a valid estimate and examination on its osteohistology and growth, so the results for E. regalis aren't statistically significant. [11]
The skull was roughly triangular in profile. [12] One specimen preserved a soft tissue crest or wattle on top of its head. [2] The beak was toothless, with both the upper and lower beaks being extended by keratinous material. [9] Its teeth were present only in the maxillae (upper cheeks) and dentaries (main bone of the lower jaw). [13] [14] They grew in columns, with an observed maximum of six in each and the number of columns varied based on the animal's size. [6] There were 51 to 53 columns per maxilla and 48 to 49 per dentary (teeth of the upper jaw being slightly narrower than those in the lower jaw). [12]
E. regalis had thirteen neck vertebrae, eighteen back vertebrae, nine hip vertebrae, and an unknown number of tail vertebrae. [12] The front legs were shorter and less heavily built than the back legs. Each hand had four fingers, but no thumb (first finger). The second, third, and fourth fingers were approximately the same length and unified in life within a fleshy covering. Although the second and third finger had hoof-like claws, these bones were also within the skin and not apparent from the outside. The little finger was separate from the other three and was much shorter. [15] Each foot had three toes, with no big toe or little toe. The toes had keratinous hoof-like tips. [6]
The first known fossil remains that may belong to Edmontosaurus regalis were named Trachodon cavatus in 1871 by Edward Drinker Cope. [16] The name is spelled in more recent sources as Trachodon avatus [7] or as Trachodon atavus. [9] [17] This species was assessed without comment as a synonym of Edmontosaurus regalis in two reviews, [9] [17] although T. atavus predates E. regalis by several decades. In 1874, Cope named (but did not describe) Agathaumas milo for a sacral vertebra and shin fragments from the late Maastrichtian-age Upper Cretaceous Laramie Formation of Colorado. [7] [18] [19] Later that same year, he described these bones under the name Hadrosaurus occidentalis. [7] [19] [20] Sadly, the bones are now lost to history. [19] As with Trachodon atavus, Agathaumas milo has been assigned without comment to Edmontosaurus regalis in two reviews, [9] [17] although predating E. regalis by several decades. Neither species has attracted much attention, as both are absent from Lull and Wright's 1942 monograph, for example. A third and obscure early species, Trachodon selwyni, described by Lawrence Lambe in 1902 for a lower jaw from what is now known as the Dinosaur Park Formation of Alberta, [21] was erroneously described by Glut (1997) as having been assigned to Edmontosaurus regalis by Lull and Wright. [7] It was not, instead being designated "of very doubtful validity." [22] More recent reviews of hadrosaurids have concurred. [9] [17]
The type specimen of E. regalis is NMC 2288, which consists of a skull, articulated vertebrae up to the sixth tail vertebra, ribs, partial hips, an upper arm bone, and most of a hind limb. It was discovered in 1912 by Levi Sternberg. The second specimen, paratype NMC 2289, consists of a skull and skeleton lacking the beak, most of the tail, and part of the feet. It was discovered in 1916 by George F. Sternberg. Both skeletons were found in the Horseshoe Canyon Formation (formerly the lower Edmonton Formation) along the Red Deer River of southern Alberta. [23] Thus, the Edmonton Formation lent Edmontosaurus its name. [24] The name Edmontosaurus regalis (meaning "regal," or, more loosely, "king-sized"), [24] was coined in 1917 by Lawrence Lambe. Lambe found that his new dinosaur compared best to specimens of " Diclonius mirabilis " (now assigned to Edmontosaurus annectens ) and drew attention to the size and robustness of Edmontosaurus regalis. [23] Initially, Lambe only described the skulls of the two skeletons, but returned to the genus in 1920 to describe the skeleton of NMC 2289. [3] The postcrania of the type specimen remains undescribed, still in its plaster jackets. [7]
Two more species that would come to be included with Edmontosaurus regalis were named from Canadian remains in the 1920s, but both would initially be assigned to the dubious genus Thespesius . Gilmore named the first, Thespesius edmontoni, in 1924. T. edmontoni also came from the Horseshoe Canyon Formation. It was based on NMC 8399, another nearly complete skeleton lacking most of the tail. NMC 8399 was discovered on the Red Deer River in 1912 by a Sternberg party. [4] Its forelimbs, ossified tendons, and skin impressions were briefly described in 1913 and 1914 by Lambe, who at first thought it was an example of a species he'd named Trachodon marginatus, [25] but he changed his mind. [26] The specimen became the first dinosaur skeleton to be mounted for exhibition in a Canadian museum. Gilmore found that his new species compared closely to what he called Thespesius annectens , but left the two apart because of details of the arms and hands. He also noted that his species had more vertebrae than Marsh's in the back and neck, but proposed that Marsh was mistaken in assuming that the annectens specimens were complete in those regions. [4]
In 1926, Charles Mortram Sternberg named Thespesius saskatchewanensis for NMC 8509, which is 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, [5] now the Frenchman Formation. [9] NMC 8509 included an almost complete skull, numerous vertebrae, partial shoulder and hip girdles, and partial legs. This represented 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. [5] T. saskatchewanensis was unusual because of its small size, estimated at 7 to 7.3 metres (23 to 24 ft) in length. [12]
The cladogram below follows an analysis from Godefroit et al. (2012). [27]
In a 2011 study, Campione and Evans recorded data from all known edmontosaur skulls and used it to plot a morphometric graph, comparing variable features of the skull with skull size. Their results showed that within Edmontosaurus regalis, many features previously used to classify additional species were directly correlated with skull size. Campione and Evans interpreted these results as strongly suggesting that the shape of E. regalis skulls changed dramatically as they grew. This has led to several apparent mistakes in past classification. The Campanian species Thespesius edmontoni, previously considered a synonym of E. annectens because of its small size and skull shape, is more likely a subadult specimen of E. regalis. [28] In a 2014 study, researchers proposed that E. regalis reached maturity at 10-15 years of age. [29] A preserved rhamphotheca present in specimen LACM 23502, housed in the Los Angeles County Museum, also indicates the beak of the related Edmontosaurus annectens was more hook-shaped and extensive than many illustrations in scientific and public media have previously depicted. Whether this was true of E. regalis as well is still unknown as of this time. [30] [31]
Extensive bone beds are known for Edmontosaurus regalis and such groupings of hadrosaurids are used to suggest that they were gregarious, living in herds. [9] Two quarries containing E. regalis remains were identified in a 2007 database of fossil bone beds, including ones in Alaska (Prince Creek Formation) and Alberta (Horseshoe Canyon Formation). [32]
The Edmontonian land vertebrate age is defined by the first appearance of Edmontosaurus regalis in the fossil record. [33] Although sometimes reported as of exclusively the early Maastrichtian age, [34] the Horseshoe Canyon Formation was of somewhat longer duration. Deposition began approximately 73 million years ago, in the late Campanian, and ended between 68.0 and 67.6 million years ago. [35] Edmontosaurus regalis is known from the lowest of five units within the Horseshoe Canyon Formation, but is absent from at least the second to the top. [36]
Because of its wide distribution, which covers a distance from Alaska to Colorado and includes polar settings that would have had little light during a significant part of the year, Edmontosaurus regalis has been considered possibly migratory. A 2008 review of dinosaur migration studies by Phil R. Bell and Eric Snively proposed that E. regalis was capable of an annual 2,600 kilometres (1,600 mi) round-trip journey, provided it had the requisite metabolism and fat deposition rates. Such a trip would have required walking speeds of about 2 to 10 kilometres per hour (1 to 6 mph) and could have brought it from Alaska to Alberta. The possible migratory nature of E. regalis contrasts with many other dinosaurs, such as theropods, sauropods, and ankylosaurians, which Bell and Snively found were more likely to have overwintered. [37] [38] In contrast to Bell and Snively, Anusuya Chinsamy and colleagues concluded from a study of bone microstructure that polar edmontosaurs overwintered. [39]
As many as three quarters of the dinosaur specimens from the badlands near Drumheller may pertain to Edmontosaurus regalis. [40] The Horseshoe Canyon Formation is interpreted as having a significant marine influence, due to the encroaching Western Interior Seaway. This shallow sea stretched from the Gulf of Mexico to the Arctic Ocean, covering the midsection of North America through much of the Cretaceous. [41] E. regalis shared this setting with fellow hadrosaurids Hypacrosaurus and Saurolophus , the parksosaurid Parksosaurus , the ceratopsids Montanoceratops , Anchiceratops , Arrhinoceratops , and Pachyrhinosaurus , the pachycephalosaurid Stegoceras , the ankylosaurid Euoplocephalus , the nodosaurid Edmontonia , the ornithomimids Ornithomimus and Struthiomimus , a variety of poorly known small theropods that included troodontids and dromaeosaurids, and the tyrannosaurid Albertosaurus . [34]
Edmontosaurus is found in coastal, near-marine settings, while Hypacrosaurus and Saurolophus are found in more continental lowlands. [42] Edmontosaurus and Saurolophus are not usually found together. [43] The typical edmontosaur habitat of this formation has been described as the back regions of bald cypress swamps and peat bogs on delta coasts. Pachyrhinosaurus also preferred this habitat to the floodplains dominated by Hypacrosaurus, Saurolophus, Anchiceratops, and Arrhinoceratops. [40] The Edmontonian-age coastal Pachyrhinosaurus-Edmontosaurus association is recognized as far north as Alaska. [44]
Trachodon is a dubious genus of hadrosaurid dinosaur based on teeth from the Campanian-age Upper Cretaceous Judith River Formation of Montana, U.S. It is a historically important genus with a convoluted taxonomy that has been all but abandoned by modern dinosaur paleontologists.
Hadrosaurids, or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which includes genera such as Edmontosaurus and Parasaurolophus, was a common group of herbivores during the Late Cretaceous Period. Hadrosaurids are descendants of the Late Jurassic/Early Cretaceous iguanodontian dinosaurs and had a similar body layout. Hadrosaurs were among the most dominant herbivores during the Late Cretaceous in Asia and North America, and during the close of the Cretaceous several lineages dispersed into Europe, Africa, and South America.
Edmontosaurus, often colloquially and historically known as Anatosaurus or Anatotitan, is a genus of hadrosaurid (duck-billed) dinosaur. It contains two known species: Edmontosaurus regalis and Edmontosaurus annectens. Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian age of the Cretaceous period 73 million years ago, while those of E. annectens were found in the same geographic region from rocks dated to the end of the Maastrichtian age, 66 million years ago. Edmontosaurus was one of the last non-avian dinosaurs to ever exist, and lived alongside dinosaurs like Triceratops, Tyrannosaurus, Ankylosaurus, and Pachycephalosaurus shortly before the Cretaceous–Paleogene extinction event.
Pachyrhinosaurus is an extinct genus of centrosaurine ceratopsid dinosaur from the Late Cretaceous period of North America. The first examples were discovered by Charles M. Sternberg in Alberta, Canada, in 1946, and named in 1950. Over a dozen partial skulls and a large assortment of other fossils from various species have been found in Alberta and Alaska. A great number were not available for study until the 1980s, resulting in a relatively recent increase of interest in Pachyrhinosaurus.
Lambeosaurus is a genus of hadrosaurid dinosaur that lived about 75 million years ago, in the Late Cretaceous period of North America. This bipedal/quadrupedal, herbivorous dinosaur is known for its distinctive hollow cranial crest, which in the best-known species resembled a mitten. Several possible species have been named, from Canada, the United States, and Mexico, but only the two Canadian species are currently recognized as valid.
Claosaurus is a genus of hadrosauroid dinosaur that lived during the Late Cretaceous Period (Santonian-Campanian).
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. It is known from the remains of two species that spanned 75 to 67 million years ago, in the Late Cretaceous of Alberta, Canada, and Montana, United States, and is the latest hollow-crested duckbill known from good remains in North America. It was an obscure genus until the discovery in the 1990s of nests, eggs, and hatchlings belonging to H. stebingeri.
Saurolophus is a genus of large hadrosaurid dinosaur from the Late Cretaceous period of Asia and North America, that lived in what is now the Horseshoe Canyon and Nemegt formations about 70 million to 66 million years ago. It is one of the few genera of dinosaurs known from multiple continents. The type species, S. osborni, was described by Barnum Brown in 1912 from Canadian fossils. A second valid species, S. angustirostris, is represented by numerous specimens from Mongolia, and was described by Anatoly Konstantinovich Rozhdestvensky.
Gryposaurus was a genus of duckbilled dinosaur that lived about 80 to 75 million years ago, in the Late Cretaceous of North America. Named species of Gryposaurus are known from the Dinosaur Park Formation in Alberta, Canada, and two formations in the United States: the Lower Two Medicine Formation in Montana and the Kaiparowits Formation of Utah. A possible additional species from the Javelina Formation in Texas may extend the temporal range of the genus to 66 million years ago.
Kritosaurus is an incompletely known genus of hadrosaurid (duck-billed) dinosaur. It lived about 74.5-66 million years ago, in the Late Cretaceous of North America. The name means "separated lizard", but is often mistranslated as "noble lizard" in reference to the presumed "Roman nose".
Anchiceratops is an extinct genus of chasmosaurine ceratopsid dinosaur that lived approximately 72 to 71 million years ago during the latter part of the Cretaceous Period in what is now Alberta, Canada. Anchiceratops was a medium-sized, heavily built, ground-dwelling, quadrupedal herbivore that could grow up to an estimated 4.3 metres (14 ft) long. Its skull featured two long brow horns and a short horn on the nose. The skull frill was elongated and rectangular, its edges adorned by coarse triangular projections. About a dozen skulls of the genus have been found.
Montanoceratops is an extinct genus of small ceratopsian dinosaur that lived approximately 70 million years ago during the latter part of the Cretaceous Period in what is now Montana and Alberta. Montanoceratops was a small sized, moderately-built, ground-dwelling, quadrupedal herbivore, that could grow up to an estimated 2.5 m (8.2 ft) in length and 170 kg (370 lb) in body mass.
Claorhynchus is a dubious genus of cerapodan dinosaur with a confusing history behind it. It has been considered to be both a hadrosaurid and a ceratopsid, sometimes the same as Triceratops, with two different assignments as to discovery formation and location, and what bones make up its type remains.
Thespesius is a dubious genus of hadrosaurid dinosaur from the late Maastrichtian-age Upper Cretaceous Lance Formation of South Dakota.
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. Its fossils have been found in the late Campanian-age Upper Cretaceous Dinosaur Park Formation in Alberta, and the roughly contemporaneous Two Medicine Formation in Montana, dating to around 75.5-74.0 million years ago. Its most recognizable feature is a small solid crest formed by the nasal bones, sticking up in front of the eyes.
The Edmontosaurus mummy AMNH 5060 is an exceptionally well-preserved fossil of a dinosaur in the collection of the American Museum of Natural History (AMNH). Discovered in 1908 in the United States near Lusk, Wyoming, it was the first dinosaur specimen found to include a skeleton encased in skin impressions from large parts of the body. It is ascribed to the species Edmontosaurus annectens, a hadrosaurid. The mummy was found by fossil hunter Charles Hazelius Sternberg and his three sons in the Lance Formation. Although Sternberg was working under contract to the British Museum of Natural History, Henry Fairfield Osborn of the AMNH managed to secure the mummy. Osborn described the fossil in detail in 1912, coining the name "dinosaur mummy" for it—several dinosaur mummies of similar preservation have been discovered since then. This specimen has considerably influenced the scientific conception of hadrosaurids. Skin impressions found in between the fingers were once interpreted as interdigital webbing, bolstering the now-rejected perception of hadrosaurids as aquatic animals, a hypothesis that remained unchallenged until 1964. Today, the mummy is considered one of the most important fossils of the AMNH.
Edmontosaurus annectens, often colloquially and historically known as the Anatosaurus, is a species of flat-headed saurolophine hadrosaurid dinosaur from the late Maastrichtian age at the very end of the Cretaceous period, in what is now western North America. Remains of E. annectens have been preserved in the Frenchman, Hell Creek, and Lance Formations. All of these formations are dated to the late Maastrichtian age of the Late Cretaceous period, which represents the last three million years before the extinction of the dinosaurs. E. annectens is also found in the Laramie Formation, and magnetostratigraphy suggests an age of 69–68 Ma for the Laramie Formation. 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, North Dakota, Wyoming, and Colorado, as well as the Canadian province of Saskatchewan. It had an extremely long and low skull, and was quite a large animal, growing up to approximately 12 metres (39 ft) in length and 5.6 metric tons in average asymptotic body mass, although it could have been even larger. E. annectens exhibits one of the most striking examples of the "duckbill" snout that is common to hadrosaurs. It has a long taxonomic history, and specimens have at times been classified as Diclonius, Trachodon, Hadrosaurus, Claosaurus, Thespesius, Anatosaurus, and Anatotitan before all being grouped together in Edmontosaurus
Hadrosaurids, also commonly referred to as duck-billed dinosaurs or hadrosaurs, were large terrestrial herbivores. The diet of hadrosaurid dinosaurs remains a subject of debate among paleontologists, especially regarding whether hadrosaurids were grazers who fed on vegetation close to the ground, or browsers who ate higher-growing leaves and twigs. Preserved stomach content findings have indicated they may have been browsers, whereas other studies into jaw movements indicate they may have been grazers.
This timeline of hadrosaur research is a chronological listing of events in the history of paleontology focused on the hadrosauroids, a group of herbivorous ornithopod dinosaurs popularly known as the duck-billed dinosaurs. Scientific research on hadrosaurs began in the 1850s, when Joseph Leidy described the genera Thespesius and Trachodon based on scrappy fossils discovered in the western United States. Just two years later he published a description of the much better-preserved remains of an animal from New Jersey that he named Hadrosaurus.
The Edmontosaurus mummy SMF R 4036 is an exceptionally well-preserved dinosaur fossil in the collection of the Naturmuseum Senckenberg (SM) in Frankfurt am Main, Germany. Found in 1910 in Wyoming, United States, it is ascribed to the species Edmontosaurus annectens, a member of the Hadrosauridae. The fossil comprises a nearly complete skeleton that was found wrapped in impressions of its skin, a rare case of exceptional preservation for which the term "dinosaur mummy" has been used. Notably, the horny beak is preserved with this specimen. Plant remains found within the thorax cavity had been interpreted as stomach contents, although later research questioned this identification. The mummy's hands are wrapped in skin impression, which was interpreted as evidence for interdigital webbing and an aquatic lifestyle in hadrosaurids; this hypothesis, although universally accepted once, is now widely refused. SMF R 4036 is one of the four best preserved hadrosaurid mummies, and was the second to be discovered. The find was made by fossil hunter Charles Hazelius Sternberg and his sons, who sold their numerous finds to various museums in North America and Europe. Only two years earlier the Sternbergs had discovered the Edmontosaurus mummy AMNH 5060 in the same region, which is now on display at the American Museum of Natural History (AMNH) in New York City.
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