Edmontosaurus annectens
Edmontosaurus annectens was one of the largest plant-eating dinosaurs of the very end of the Cretaceous and a member of the hadrosaurids, the so-called duck-billed dinosaurs. Adults reached roughly 9–12 metres in length and weighed an estimated 4–9 tonnes, with a few exceptionally large individuals possibly heavier still.
Edmontosaurus
Edmontosaurus annectens
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Weight
4000–9000 kg
Length
9–12 m
Diet
Herbivore
Period
Cretaceous
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Edmontosaurus next to Tyrannosaurus rex and a human, to the same scale.
Edmontosaurus annectens
Tyrannosaurus rex
4000–9000 kg
9–12 m
Cretaceous
Both bipedal and quadrupedal
3–4.5 m
30 km/h
Herbivore
30 recorded fossil finds in United States and Canada. Most in Wyoming, Montana, and South Dakota. First described in 1892 by Marsh.
Sites and counts from the Paleobiology Database
The timeline shows the whole age of dinosaurs – and how much time has passed since. The glowing part is when Edmontosaurus lived.
million years ago
Lived 68–66 million years ago
If the whole age of dinosaurs were a single day, Edmontosaurus lived at 23:52.
Chapter • Meet the dinosaur
Edmontosaurus annectens was one of the largest plant-eating dinosaurs of the very end of the Cretaceous and a member of the hadrosaurids, the so-called duck-billed dinosaurs. Adults reached roughly 9–12 metres in length and weighed an estimated 4–9 tonnes, with a few exceptionally large individuals possibly heavier still. The skull was long and low, ending in a broad, toothless beak that gives the group its nickname. Behind that beak sat one of the most sophisticated chewing systems ever evolved: dental batteries containing many hundreds of tightly packed teeth that ground plant material into pulp. The body was heavily built, and the tail was stiffened by ossified tendons and carried horizontally, never dragging on the ground. Skin impressions show small pebbly scales rather than feathers, and in the close relative Edmontosaurus regalis a fleshy comb-like crest sat on top of the head.
Chapter • Where it lived
Edmontosaurus annectens lived about 68–66 million years ago, during the final part of the Cretaceous (the Maastrichtian), in western North America. The landscape was a mosaic of broad floodplains, meandering rivers, swamps and forests of conifers, ginkgoes and early flowering plants, close to the shrinking shoreline of the Western Interior Seaway. Fossils come mainly from the Hell Creek Formation of Montana and the Dakotas, the Lance Formation of Wyoming, and the Frenchman Formation of Saskatchewan, Canada. It therefore shared its world with Tyrannosaurus rex, Triceratops and Ankylosaurus right up to the mass extinction that closed the Cretaceous.
Chapter • Wild behavior
Diurnal
Its dental batteries held well over a thousand teeth, continuously replaced as they wore down.
It could move both on all fours and rear up on its hind legs — a facultatively bipedal gait.
Famous 'dinosaur mummies' with preserved skin impressions were collected by the Sternberg family in Wyoming from 1908 onwards.
One Edmontosaurus tail vertebra carries a healed Tyrannosaurus rex bite mark, proving the animal survived the attack.
Anatotitan copei, long treated as its own genus, is now usually regarded as the same animal as Edmontosaurus annectens.
The species was first described in 1892 by Othniel Charles Marsh, but under the name Claosaurus annectens.
Enormous bone beds containing thousands of individuals suggest Edmontosaurus lived in large herds.
Despite the beak, there were no teeth at the front of the mouth — all chewing happened far back in the jaws.
Chapter • Scientific place
Vertebrate Anatomy Morphology Palaeontology (University of Alberta Libraries)
Reviewed: 9/4/2026
Peer-reviewed paper that formally places Edmontosaurus annectens within Ornithischia, Ornithopoda and Hadrosauridae, documenting the species' taxonomic assignment.
Open sourcePLOS ONE
Reviewed: 9/4/2026
Documents a major Edmontosaurus annectens bonebed locality in the Upper Cretaceous (Lance Formation) of Wyoming, evidencing the taxon's geographic and stratigraphic occurrence in western North America.
Open sourceCretaceous Research (open-access full text via DiVA)
Reviewed: 9/4/2026
Reconstructs the latest Cretaceous floodplain vegetation and terrestrial palaeoenvironment inhabited by a hadrosaurid in Montana, the setting in which Edmontosaurus annectens lived.
Open sourceProceedings of the National Academy of Sciences (PNAS)
Reviewed: 9/4/2026
Dental microwear study of Edmontosaurus teeth showing plant-based (herbivorous) grinding chewing and the jaw mechanics used to process tough vegetation.
Open sourceJournal of Anatomy
Reviewed: 9/4/2026
Extinct taxon; conservation status NE
Open sourceNatural History Museum, London
Reviewed: 9/4/2026
Museum overview of Edmontosaurus covering its size, anatomy, age, diet and distribution, used as the general reference for the sv, en, da and no description texts.
Open sourceNatural History Museum, London
Reviewed: 9/4/2026
Museum overview of Edmontosaurus covering its size, anatomy, age, diet and distribution, used as the general reference for the sv, en, da and no description texts.
Open sourceNatural History Museum, London
Reviewed: 9/4/2026
Museum overview of Edmontosaurus covering its size, anatomy, age, diet and distribution, used as the general reference for the sv, en, da and no description texts.
Open sourceNatural History Museum, London
Reviewed: 9/4/2026
Museum overview of Edmontosaurus covering its size, anatomy, age, diet and distribution, used as the general reference for the sv, en, da and no description texts.
Open source