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Edmontonia

A large plant-eating, armoured dinosaur

WWD - Prehistoric Planet

Edmontonia is an ankylosaur, a type of plant-eating, armoured dinosaur that was covered in bony plates called osteoderms. These osteoderms took different forms in different ankylosaurs. Ankylosaurus, for example, had bony plates, a club tail and four large pyramid-shaped horns projecting from its skull, while Edmontonia lacked a club tail, but had spiky osteoderms.

They call it home

Ankylosaurs had a worldwide distribution, although they are yet to be found in Africa. In Late Cretaceous North America, Edmontonia lived along the western shore of a shallow sea. Home was a coastal plain with a sub-tropical, warm, humid climate. In the Isle of Wight, Polacanthus lived in a riverine, floodplain environment.

What big teeth you have

What big teeth you have

Most ankylosaurs had small, leaf-shaped teeth for cropping vegetation. Unlike other herbivorous dinosaurs, like ceratopsids and hadrosaurs, ankylosaurs did not have batteries of teeth, which means they would not have been as effective in grinding up plant material.

Nose knowledge

Nose knowledge

Ankylosaurs like Edmontonia had a highly developed sense of smell, thanks to an extensive and uniquely folded nasal passage. This would have helped them seek out food as well as avoid predators.

The most fantastic find

The most fantastic find

Barnum Brown discovered a number of fossils of Ankylosaurus, the largest ankylosaur. The first reconstructions were made without the animal's characteristic tail club. Then in 1910, Brown discovered his third fossil of Ankylosaurus in the Scollard Formation. It included a complete skull, the first known tail club, ribs, limb bones and armour. These fossils are housed at the American Museum of Natural History.

Edmontonia features

Edmontonia features Height: 2m (6.56ft)
Length: 6.6m (21.65ft)
Weight: 3.5 tonnes (3.92 short tons)
Top speed: 10kph (6.21mph)
Vision: Edmontonia probably had relatively bad vision.
Skin: Edmontonia had massive bony plates and knobs of bone embedded into their skin. This was overlain by a tough, horny layer of keratin. Edmontonia's plates were not fused together, allowing their armour to deform slightly under pressure and making the animal more immune to puncture wounds. The bones within Edmontonia's triangular skull were fused, which imparted greater strength.
Brain: Ankylosaurs like Edmontonia had the smallest brains relative to body size of any dinosaur.
Prey: Its hindlimbs were longer than its forelimbs and its skull was set low, allowing it to take advantage of tender, ground-level plants and ferns.
Bite: Edmontonia did not spend much time chewing its food. Its large barrel-shaped body suggests food might have been digested by fermentation, like a modern-day cow.
Nest: We can guess from similar dinosaurs that ankylosaurs like Edmontonia laid eggs much like modern turtles, and they would have deposited 20-30 rounded eggs in a heap.

Edmontonia facts and theories

Edmontonia facts and theories

  1. Edmontonia and Ankylosaurus were ankylosaurs. Ankylosaurid ankylosaurs such as Ankylosaurus also had a club tail for defence, while nodosaurids like Edmontonia had no club, but some of their osteoderms were spiky. Ankylosaurs are members of the larger group Ornithischia, which are the beaked, herbivorous dinosaurs of the Mesozoic.
  2. Baby ankylosaurs were not very well protected and might have entirely lacked the bony ‘helmet’ which adults had on their heads. Because of this, scientists believe that infants might have stayed together in groups for protection.
  3. Ankylosaurs could swing their tail in a 100⁰ lateral arc. The largest clubs could generate between 364 and 718 megapascals of impact stress and could crush bone.
  4. Edmontonia was a nodosaurid ankylosaur, meaning it did not have the dangerous club tail that ankylosaurids like Ankylosaurus had. However, its osteoderms were quite spiky. It is possible that when it was threatened it just hunkered down on the ground to protect its relatively defenceless belly until the predator attacking it got bored.
  5. A close relative of Edmontonia, an ankylosaur called Antarctopelta, was the first dinosaur fossil ever discovered in Antarctica. The partial skeleton was found on James Ross Island in 1986.