Research reviewed 30 July 2026. Scientific interpretations may change as new evidence is published.
Ankylosaurus magniventris was a huge armoured herbivore that lived in western North America near the very end of the age of dinosaurs. Fossils show that it had a broad body, bony armour and a tail club, but no complete skeleton has ever been found.
| Fact | Evidence based answer |
|---|---|
| Scientific name | Ankylosaurus magniventris |
| Time | Late Cretaceous, about 68 to 66 million years ago |
| Place | Present day Montana, Wyoming and Alberta |
| Diet | Herbivore |
| Length | About 6 to 8 metres |
| Mass | Roughly 5 to 8 tonnes, with considerable uncertainty |
| Main features | Skin armour, a broad skull and a heavy tail club |
Ankylosaurus belonged to a group of armoured dinosaurs called ankylosaurs. Its name means “fused lizard”, a reference to the firmly joined bones in parts of its skull and body. The species name magniventris means “great belly”, which suits its unusually wide ribcage.
It was not shaped like a giant lizard with a few plates placed on top. It had a low, broad body carried on four strong legs. Small leaf shaped teeth and a wide beak were suited to gathering vegetation. Much of its back, neck and sides was protected by bones called osteoderms that grew within the skin.
Ankylosaurus lived about 68 to 66 million years ago, during the final part of the Late Cretaceous. Its fossils come from rocks including the Hell Creek Formation in Montana, the Lance Formation in Wyoming and the Scollard Formation in Alberta.
These environments included rivers, floodplains, forests and open areas. Ankylosaurus shared this world with Tyrannosaurus rex, Triceratops and Edmontosaurus. All of them lived close to the mass extinction that ended the age of non bird dinosaurs.
The armour of Ankylosaurus was made from many separate osteoderms rather than one solid shell. Some were broad and flat, while others formed knobs or pointed structures. Their exact arrangement is difficult to reconstruct because osteoderms often moved away from the body after death.
The end of the tail carried two large osteoderms that formed a club. The final tail vertebrae were stiffened into a handle, while the front part of the tail remained more flexible. Studies of related ankylosaurid tails suggest that a large club could deliver a powerful sideways strike.
Its heavy body and short limbs do not suggest a fast runner. It was probably a steady four legged walker, although fossils cannot tell us its exact top speed.
Ankylosaurus was a herbivore. Its head was held close to the ground, so it probably fed on ferns, shrubs, low branches, fruit and other vegetation within easy reach.
The beak could crop plants, while its small teeth performed limited processing. A very wide torso provided space for a large digestive system in which microbes may have helped break down tough plant material. Claims about an exact daily food total are estimates rather than facts preserved in fossils.
Ankylosaurus is famous but surprisingly incomplete. Scientists know it from only a handful of specimens, including partial skulls, vertebrae, limb bones, armour and a well preserved tail club. The most complete known body still has major gaps.
A modern anatomical study estimated one smaller individual at about 4.78 tonnes, with a large error range. The largest known skull may represent an animal near 8 tonnes, but that result is tentative because the rest of its body was not found. For a school project, “about 6 to 8 metres long and roughly 5 to 8 tonnes” is an honest summary.
Scientists are still working out the exact arrangement of the armour and the proportions of missing body parts. Older reconstructions sometimes reached nearly 10 metres, but modern researchers consider about 8 metres more reasonable for a very large individual.
Defensive use is the leading explanation for the tail club. Biomechanical models show that large ankylosaurid clubs could strike hard enough to damage bone, but no fossil records a living swing. The club might also have played a role in contests between members of the same species.
Ankylosaurus did not wear one unbroken shell like a turtle. Its armour consisted of many osteoderms embedded in the skin.
Not every ankylosaur had a tail club. Nodosaurids had extensive armour but lacked the large bony club seen in Ankylosaurus.
Scientists have not proved that every club strike targeted a predator. Defence is well supported, while other possible behaviours remain open to study.
The name means “fused lizard”. It refers to firmly joined bones in parts of the skeleton.
Yes. Their fossils occur in rocks of similar age in western North America.
Most armour grew within the skin rather than attaching directly to the backbone.
Models of large ankylosaurid clubs show that powerful strikes could damage bone. Exact behaviour is inferred rather than observed.
It probably ate low growing ferns, shrubs, fruit and leafy plants.
Large individuals were probably about 6 to 8 metres long. Mass estimates range from roughly 5 to 8 tonnes.
No. Every known specimen is incomplete, so relatives help researchers reconstruct missing parts.
A broad ribcage supported a large gut that could process great quantities of plant food.
