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Edmontosaurus annectens
Edmontosaurus annectens (meaning "connected lizard from Edmonton"), often colloquially and historically known as Anatosaurus (meaning "duck lizard"), 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 non-avian dinosaurs (between 68 and 66 million years ago). 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 (6.2 short 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.
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 the author and date.
The history of E. annectens predates the naming of both the genus Edmontosaurus and the species annectens. The first quality specimen, the former holotype 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 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 its pelvis and part of its torso due to a stream cutting through it. The bill had impressions of a horn-like 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 the species Diclonius mirabilis. This species name was created by combining Diclonius, a hadrosaurid genus Cope had named earlier from teeth, with Trachodon mirabilis, an older name based on teeth that was published by Joseph Leidy. Cope believed that Leidy had failed to properly characterize the genus Trachodon and later abandoned its use, so he assigned the old species to his newer genus. Leidy had come to recognize that his Trachodon was based on the remains of multiple kinds of dinosaurs, and although he had made some attempts to revise the genus, he had not yet made any formal declaration of his intentions.
Cope's description promoted hadrosaurids as amphibious animals, 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 eat terrestrial food; he described the beak as weak, too. However, aside from misidentifying several of the skull bones, by chance, the lower jaws were missing the walls supporting the teeth from the inside, and the teeth were actually very well-supported. Cope intended to describe the skeleton and 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 arch-rival, Othniel Charles Marsh, published a paper on a sizable lower jaw recovered by John Bell Hatcher in 1889 from the Lance Formation rocks in Niobrara County, Wyoming. Marsh named this partial jaw Trachodon longiceps, and 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 that is 92.0 centimetres (36.2 in) long, whereas Marsh's dentary is estimated at 110.0 centimetres (43.3 in) long.
A second mostly complete skeleton, AMNH 5886, was found in 1904 in the Hell Creek Formation rocks at Crooked Creek in central Montana by a local rancher named Oscar Hunter. 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 1908, these two specimens were 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 alongside 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, being designated as 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, as it is among the first dinosaurs to receive a skeletal restoration, and is the first hadrosaurid so restored. 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 was put on display in 1904.
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Edmontosaurus annectens
Edmontosaurus annectens (meaning "connected lizard from Edmonton"), often colloquially and historically known as Anatosaurus (meaning "duck lizard"), 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 non-avian dinosaurs (between 68 and 66 million years ago). 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 (6.2 short 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.
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 the author and date.
The history of E. annectens predates the naming of both the genus Edmontosaurus and the species annectens. The first quality specimen, the former holotype 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 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 its pelvis and part of its torso due to a stream cutting through it. The bill had impressions of a horn-like 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 the species Diclonius mirabilis. This species name was created by combining Diclonius, a hadrosaurid genus Cope had named earlier from teeth, with Trachodon mirabilis, an older name based on teeth that was published by Joseph Leidy. Cope believed that Leidy had failed to properly characterize the genus Trachodon and later abandoned its use, so he assigned the old species to his newer genus. Leidy had come to recognize that his Trachodon was based on the remains of multiple kinds of dinosaurs, and although he had made some attempts to revise the genus, he had not yet made any formal declaration of his intentions.
Cope's description promoted hadrosaurids as amphibious animals, 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 eat terrestrial food; he described the beak as weak, too. However, aside from misidentifying several of the skull bones, by chance, the lower jaws were missing the walls supporting the teeth from the inside, and the teeth were actually very well-supported. Cope intended to describe the skeleton and 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 arch-rival, Othniel Charles Marsh, published a paper on a sizable lower jaw recovered by John Bell Hatcher in 1889 from the Lance Formation rocks in Niobrara County, Wyoming. Marsh named this partial jaw Trachodon longiceps, and 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 that is 92.0 centimetres (36.2 in) long, whereas Marsh's dentary is estimated at 110.0 centimetres (43.3 in) long.
A second mostly complete skeleton, AMNH 5886, was found in 1904 in the Hell Creek Formation rocks at Crooked Creek in central Montana by a local rancher named Oscar Hunter. 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 1908, these two specimens were 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 alongside 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, being designated as 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, as it is among the first dinosaurs to receive a skeletal restoration, and is the first hadrosaurid so restored. 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 was put on display in 1904.