Edmontosaurus ("lizard from Edmonton") is a hadrosaurid dinosaur species from the Maastrichtian, the last phase of the Cretaceous period, 71-65 million years ago. A fully-grown adult could have been up to nine meters long, and some of the larger species reached thirteen meters. Its weight was in the region of 3.5 tones, making it one of the largest hadrosaurids.


Lawrence M. Lambe erected Edmontosaurus in 1917 from a find in the Edmonton Rock Formation, Alberta; using E. regales as type species. Marsh named Claosaurus annectens in 1892, but this has now been reclassified as E. annectens. Likewise, Charles Mortram Sternberg named Thespesius in 1926, but this is also a class of Edmontosaurus, namely E. saskatchewanensis.

Edmontosaurus Dinosaur


Edmontosaurus could pass the toughest foodstuff back and forth across the teeth with its muscular daring pouches.

To fit so many teeth into its mouth, they were packed into tight "banks" of up to sixty rows, and new teeth continually grew to replace lost teeth — analogous to a new shark.The bones of the higher jaw would flex outwards as lower jaw came up, so the mandible could grind against it. Typical food would have built-in conifer needles, seeds and twigs, and these have been establishing in the body cavities of fossilized edmontosaurs. It was evidently a tree-browser.


The 1908 discovery in Wyoming was particularly remarkable in that paleontologists actually recovered fossilized imprints of Edmontosaurus' skin. The skin drying very quickly and fixing its shape into the mud must have left the impression. It is from these imitations that we know the skin was scaly and leathery, and the thigh muscle was under the skin of the body. This would have given the feeling that the leg left its body at the knee, and the whole thigh was under the skin. This only contributes to its resemblance to a duck. It also had a number of tubercles (bumps) along its neck and down its back and tail.

Edmontosaurus was bipedal but could surely have walked on four legs. The forelimbs are shorter than the hinds but not adequately that four-legged motivation was unfeasible. The front feet also had hooves on two fingers, and weight-bearing pads like folks of Camarasaurus. The rear feet had two toes and all were hoofed. The bone arrangement in the lower limbs suggests that both the legs and feet were attached to very influential muscles. The spine curved downwards at the shoulders, so Edmontosaurus would have had a low posture and would have browsed close to the ground. Despite the power of the limbs, Edmontosaurus would only have been slow moving and had few defensive features. To survive, it must have had keen eyesight, hearing and smell to get early warning of predators.

The arrangement of the skull suggests it may have had loose skin around its wide nasal passages. These could have been inflatable, in order to threaten other dinosaurs or as part of the mating ritual.

The World Of Edmontosaurus

Edmontosaurus existed in the similar place and time period as Tyrannosaurus rex and one specimen on display in the Denver Museum of Nature and Science has evidence of a T. rex bite in the tail. This vicious assault on the bone suggests that the Edmontosaurus was alive at the time and hence T. rex was probably not a scavenger, as had been suggested in the 1970s. A mass cemetery discovery in Alberta, Canada suggests that edmontosaurs lived in herds. These herds may have migrated with the seasons, from the North Slope of Alaska, where plant life would have been scarce during the dark winter months, to the richer pastures of Alberta. If this were the case, T. rex would probably have gone with it, in search of a relatively easy meal.