 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 9 metres (30 ft) long, and some of the larger specimens reached the range of 12 metres (39 ft) to 13 metres (43 ft) long. Its weight was on the order of 4.0 metric tons (4.4 short tons). 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 9 to 12 metres (30 to 39 ft) long. E. annectens is often seen as smaller. Two mounted skeletons, USNM 2414 and YPM 2182, measure 8.00 metres (26.25 ft) long and 8.92 metres (29.3 ft) long, respectively. However, these are probably subadult individuals, and there is at least one report of a much larger potential E. annectens specimen, almost 12 metres (39 ft) long. Two specimens still under study in the collection of the Museum of the Rockies; a 7.6 m (25 ft) tail labelled as MOR 1142 and another labelled as MOR 1609, indicate that Edmontosaurus annectens could have been even larger, possibly rivaling Shantungosaurus in size. The specimens of these individuals indicate a length of up to 15 m (49 ft), as confirmed by paleontologists and the development team of the scientifically accurate simulation game Saurian (video game). Such large individuals of Edmontosaurus would likely have been very rare due to such factors as environmental stress, disease, and predation.
