It had short arms, a long, pointed tail, three-toed, hoofed feet, and mitten-like hands. Its head was flat and sloping with a wide, toothless beak, cheek pouches, and hundreds of closely-packed cheek teeth that ground up its food. It was about 42 feet (13 m) long and may have weighed up to 3.5 tons. It was a biped (it walked on two legs) that could also walk on four legs, perhaps to graze low-lying plants. Edmontosaurus was a slow-moving dinosaur with few defenses, but may have had keen senses (eyesight, hearing, and smell) to help it avoid predators in its swampy habitat. Edmontosaurus had leathery skin (as determined from two mummified Edmontosaurus fossils found in Wyoming). It may have had loose skin around its nose area - some paleontologists think that it may have been able to blow up this skin like a balloon, perhaps for mating rituals or intra-species rivalry. It had a series of bumps (tubercles) running along its neck, back, and tail.Edmontosaurus lived in the late Cretaceous period, about 73 to 65 million years ago, toward the end of the Mesozoic Era. It went extinct during the huge K-T mass extinction. T. rex was one of its contemporaries, and may have preyed upon Edmontosaurus.Edmontosaurus was an ornithopod, whose intelligence (as measured by its relative brain to body weight, or EQ) was midway among the dinosaurs.Edmontosaurus probably lived in herds (like many other hadrosaurs) since large numbers of Edmontosaurus have been found close to one another in Alberta, Canada.
Edmontosaurus herds may have migrated thousands of miles seasonally, traveling from the North Slope of Alaska (which would have been dark for months at a time during winter, making plants scarce) to Alberta, Canada (which was rich in green plants during winter). Large numbers of Edmontosaurus fossils have been found at both ends of this proposed migratory route.Edmontosaurus was an herbivore, a plant eater. Fossilized conifer needles have been found in Edmontosaurus' stomach. It ate conifer needles, twigs, seeds, and other plant material with its tough beak. It had no teeth in its beak, but had hundreds of cheek teeth used for grinding up tough plant material.The almost defenseless Edmontosaurus was preyed upon by Tyrannosaurus rex. T. rex may have even followed Edmontosaurus' migration routes in search of a series of good meals. Other predators of Edmontosaurus may have included Albertosaurus.Edmontosaurus could run on two legs or walk on four; it was a relatively slow dinosaur. Dinosaur speeds are estimated using their morphology (characteristics like leg length and estimated body mass) and fossilized trackways.Edmontosaurus was named by Lawrence M. Lambe in 1917 from a fossil found in Edmonton Rock Formation, in Alberta, Canada. Many Edmontosaurus fossils have been found, in Alberta, Canada, and Alaska, Wyoming, Montana and New Jersey in the USA. Two mummified Edmontosaurus fossils were found in Wyoming, USA. The dinosaur previously called Anatosaurus is probably a juvenile example of Edmontosaurus.