Euoplocephalus tutus
Euoplocephalus was one of the most heavily armoured plant-eaters that ever lived. Its body was broad, low-slung and barrel-shaped, roughly 5.3–6 metres long and weighing about 1.8–2.5 tonnes.
Euoplocephalus
Euoplocephalus tutus
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Weight
1800–2500 kg
Length
5.3–6 m
Diet
Herbivore
Period
Cretaceous
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Euoplocephalus next to Tyrannosaurus rex and a human, to the same scale.
Euoplocephalus tutus
Tyrannosaurus rex
1800–2500 kg
5.3–6 m
Cretaceous
Quadrupedal
1.4–1.8 m
10 km/h
Herbivore
6 recorded fossil finds in Canada. First described in 1902 by Lambe.
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 Euoplocephalus lived.
million years ago
Lived 76.5–75 million years ago
If the whole age of dinosaurs were a single day, Euoplocephalus lived at 22:44.
Chapter • Meet the dinosaur
Euoplocephalus was one of the most heavily armoured plant-eaters that ever lived. Its body was broad, low-slung and barrel-shaped, roughly 5.3–6 metres long and weighing about 1.8–2.5 tonnes. The back and flanks were covered by rows of bony plates called osteoderms, embedded in the skin and bound together by tough connective tissue. Wide armoured bands crossed the neck and shoulders, while stout spikes projected from the sides. Even the eyelids were bony and could be dropped like tiny shutters. Its most famous feature is the tail club: the last tail vertebrae were fused into a stiff handle ending in two large knobs of bone. The animal walked on all fours at all times, with short, powerful limbs and a horizontal back — the tail was carried clear of the ground, never dragging.
Chapter • Where it lived
Euoplocephalus lived around 76.5–75 million years ago, during the Campanian stage of the Late Cretaceous, in what is now southern Alberta, Canada. Its fossils come mainly from the lower part of the Dinosaur Park Formation in Dinosaur Provincial Park, an area that was then a humid coastal lowland on the western shore of the Western Interior Seaway. The landscape was a mosaic of braided rivers, floodplains, swampy woodlands and lagoons filled with conifers, ferns, cycads and early flowering plants. Here Euoplocephalus shared its world with hadrosaurs such as Corythosaurus, ceratopsians such as Centrosaurus, and predators such as Gorgosaurus.
Chapter • Wild behavior
Diurnal
The name means roughly "well-armoured head", referring to the fused bony plates on the skull.
Its eyelids were reinforced with bone and could be lowered like armoured shutters.
Biomechanical studies suggest the tail club could swing hard enough to break a predator's leg bone.
The nasal passages were long and looping, perhaps for cooling and humidifying air or amplifying calls.
It was first named Stereocephalus tutus, but that name was already taken by a beetle, so it was renamed in 1910.
The back armour was not a single shell but hundreds of separate plates set in the skin, rather like a crocodile's.
Euoplocephalus shared its river floodplains with the tyrannosaur Gorgosaurus.
Many fossils once labelled Euoplocephalus are now placed in the genera Anodontosaurus, Scolosaurus and Dyoplosaurus.
Chapter • Scientific place
PLOS ONE (doi:10.1371/journal.pone.0062421)
Reviewed: 9/4/2026
Peer-reviewed revision of Euoplocephalus tutus that establishes its diagnosis and placement within Ankylosauridae (Ankylosaurinae), Ankylosauria, Thyreophora, Ornithischia.
Open sourcePubMed, U.S. National Library of Medicine
Reviewed: 9/4/2026
Indexed record of the study that catalogues every referred specimen and its locality and stratigraphic position, restricting Euoplocephalus tutus to the lower Dinosaur Park Formation of southern Alberta.
Open sourcePubMed Central, U.S. National Library of Medicine
Reviewed: 9/4/2026
Full text documenting the Campanian Dinosaur Park Formation setting — a coastal-plain, river-and-floodplain palaeoenvironment on the western margin of the Western Interior Seaway — in which Euoplocephalus specimens occur alongside other Dinosaur Provincial Park dinosaurs.
Open sourcePubMed Central, U.S. National Library of Medicine
Reviewed: 9/4/2026
Peer-reviewed biomechanical analysis of ankylosaurian skulls and jaws, including Euoplocephalus, supporting a herbivorous, low-browsing feeding ecology.
Open sourcePLOS ONE (doi:10.1371/journal.pone.0062421)
Reviewed: 9/4/2026
Extinct taxon; conservation status NE
Open sourcePLOS ONE (doi:10.1371/journal.pone.0062421)
Reviewed: 9/4/2026
Comprehensive open-access redescription of Euoplocephalus tutus covering skull anatomy, osteoderm armour, tail club, body size and contemporaneous ankylosaurids, suitable as the general overview reference for the sv, en, da and no description text.
Open sourcePLOS ONE (doi:10.1371/journal.pone.0062421)
Reviewed: 9/4/2026
Comprehensive open-access redescription of Euoplocephalus tutus covering skull anatomy, osteoderm armour, tail club, body size and contemporaneous ankylosaurids, suitable as the general overview reference for the sv, en, da and no description text.
Open sourcePLOS ONE (doi:10.1371/journal.pone.0062421)
Reviewed: 9/4/2026
Comprehensive open-access redescription of Euoplocephalus tutus covering skull anatomy, osteoderm armour, tail club, body size and contemporaneous ankylosaurids, suitable as the general overview reference for the sv, en, da and no description text.
Open sourcePLOS ONE (doi:10.1371/journal.pone.0062421)
Reviewed: 9/4/2026
Comprehensive open-access redescription of Euoplocephalus tutus covering skull anatomy, osteoderm armour, tail club, body size and contemporaneous ankylosaurids, suitable as the general overview reference for the sv, en, da and no description text.
Open source