Temporal Range: Late Cretaceous (73-65.5 Mya)
Length: 12 metres
Height: 4 metres
Movement: Prominently Quadrupedal
Feeding Type: Herbivore
- Discovery: Edmontosaurus has a long, extremely complicated taxonomic history. It was officially named in 1917, although the first fossil remains were discovered in 1871 but these were incorrectly named as a species of Claosaurus in 1892. This original fossil was recovered by American palaeontologist John Bell Hatcher from Late Cretaceous rocks in Wyoming, USA. This fossil, although incorrectly named, has some historical footnotes; most notably it was the first hadrosaurid dinosaur fossil to be reconstructed and one of the first to be put on display in the USA, in 1901. In 1917, Lawrence Lambe discovered two partial skeletons in Alberta, Canada; and attributed them to a new species; Edmontosaurus. Lambe then suggested his new discovery showed more similarities to the fossil discovered by Hatcher, than the type specimen of Claosaurus did. This led to the reclassification of Hatchers early discovery, to a species of Edmontosaurus. Currently Edmontosaurus has two known species; Edmontosaurus regalis and Edmontosaurus annectens. Most researchers believe the separate genus, Anatotitan, is a species of Edmontosaurus, due to its physical similarities, however this is yet to be unanimously agreed upon.
Edmontosaurus is classified as a saurolophinae dinosaur, a clade of hadrosaurid dinosaurs who lacked the hollow head-crests. Its closest relative is the giant Chinese hadrosaurid dinosaur Shantungosaurus , which is almost anatomically identical.
- Statistics: Edmontosaurus has been described from a number of specimens, including fully grown adults, sub-adults and juveniles; meaning researchers have produced a number of accurate size estimates for Edmontosaurus. The largest species of Edmontosaurus, E. annectens, is thought to have grown to lengths of around 12 metres and weighed around 4,500kg. E. regalis is often considered the smaller species, with maximum length estimates of around 9 metres. However, some researchers believe Anatotian to represent a fully grown E. regalis, which would make both species of Edmontosaurus similarly sized.
- Description: Edmontosaurus was one of the last remaining dinosaurs, and lived alongside Triceratops and Tyrannosaurus shortly before the Cretaceous extinction event. An Edmontosaurus specimen on display in the Denver Museum of Natural History and Science shows evidence of a theropod bite mark in the tail. Researchers have proven the bite mark was most likely produced by a Tyrannosaurus attack, but as the attack was not fatal it is thought the Edmontosaurus in question likely outmanoeuvred or outrun its attacker, or that the damage on its tail was incurred by the Edmontosaurus using it as a defensive weapon against the Tyrannosaurus.
Edmontosaurus was widely distributed across western North America, but the distribution of these fossils suggests that it preferred coasts and coastal plains as habitat regions. Edmontosaurus was a herd-dwelling herbivore, who would have used its broad beak-like structure to crop plant material and then chewed this material with the hundreds of teeth that were situated further back in its mouth. The skull housed around 60 rows of these teeth on each jaw, giving Edmontosaurus a total of around 1,000 teeth. Many researchers have suggested that Edmontosaurus would have supported cheek-like structures, in which the animal would hold food prior to chewing.
Like other hadrosaurids, Edmontosaurus is thought to have been a facultative biped, meaning that it most moved quadrupedally but could move bipedally if required. It is thought that Edmontosaurus would have only moved bipedally when moving rapidly, and recent research has suggested that Edmontosaurus would have been able to move at maximum speeds of around 30mph.
Some of my early followers may notice I’ve used the same picture here as I did for my post on Anatotian. That’s because it is a great drawing, and many palaeontologists believe Anatotian and Edmontosaurus to be the same animal.