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''Edmontosaurus'' ( ) 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 stage of the Cretaceous Period 73 million years ago, while those of ''E. annectens'' were found in the same geographic region but in rocks dated to the end of the Maastrichtian stage of the Cretaceous, 66 million years ago. ''Edmontosaurus'' was one of the last non-avian dinosaurs, and lived alongside dinosaurs like ''Triceratops'' and ''Tyrannosaurus'' shortly before the Cretaceous–Paleogene extinction event. ''Edmontosaurus'' included some of the largest hadrosaurid species, measuring up to long and weighing around . Several well-preserved specimens are known that include not only bones, but in some cases extensive skin impressions and possible gut contents. It is classified as a genus of saurolophine (or hadrosaurine) hadrosaurid, a member of the group of hadrosaurids which lacked large, hollow crests, instead having smaller solid crests or fleshy combs.〔 The first fossils named ''Edmontosaurus'' were discovered in southern Alberta (named after Edmonton, the capital city), in the Horseshoe Canyon Formation (formerly called the lower Edmonton Formation). The type species, ''E. regalis'', was named by Lawrence Lambe in 1917, although several other species that are now classified in ''Edmontosaurus'' were named earlier. The best known of these is ''E. annectens'', named by Othniel Charles Marsh in 1892; originally as a species of ''Claosaurus'', known for many years as a species of ''Trachodon'', and later as ''Anatosaurus annectens''. ''Anatosaurus'' and ''Anatotitan'' are now generally regarded as synonyms of ''Edmontosaurus''. ''Edmontosaurus'' was widely distributed across western North America. The distribution of ''Edmontosaurus'' 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, ''Edmontosaurus'' is thought to have lived in groups, and may have been migratory as well. 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, such as evidence for a tyrannosaur attack on one edmontosaur specimen. ==Description== ''Edmontosaurus'' has been described in detail from numerous specimens. Like other hadrosaurids, it was a bulky animal with a long, laterally flattened tail and a head with an expanded, duck-like beak. The skull had no bony crest, unlike many other hadrosaurids, but bore a comb-like crest of skin and scales. The fore legs were not as heavily built as the hind legs, but were long enough to be used in standing or movement. ''Edmontosaurus'' was among the largest hadrosaurids: depending on the species, a fully grown adult could have been long, and some of the larger specimens reached the range of to long. Its weight was on the order of . Traditionally, ''E. regalis'' has been regarded as the largest species, though this was challenged by the hypothesis that the larger hadrosaurid ''Anatotitan copei'' is a synonym of ''Edmontosaurus annectens'', as put forward by Jack Horner and colleagues in 2004,〔 and supported in studies by Campione and Evens in 2009 and 2011.〔 The type specimen of ''E. regalis'', NMC 2288, is estimated as long.〔Lull, Richard Swann; and Wright, Nelda E. (1942). ''Hadrosaurian Dinosaurs of North America''. p. 225.〕 ''E. annectens'' is often seen as smaller. Two mounted skeletons, USNM 2414 and YPM 2182, measure long and long, respectively.〔 However, these are probably subadult individuals,〔 and there is at least one report of a much larger potential ''E. annectens'' specimen, almost long. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Edmontosaurus」の詳細全文を読む スポンサード リンク
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