Ankylosaurus magniventris
Pronounced an-KY-loh-SORE-us mag-nih-VEN-tris
Ankylosauria · Ankylosauridae
A heavily armored, club-tailed ankylosaur from the very end of the Cretaceous of western North America, the largest known member of its group and a neighbour of T. rex and Triceratops.
- Armored
- Tail club
- Quadrupedal
- Giant
- Movie icon
- Period
- Cretaceous· Maastrichtian
- Diet
- Herbivore
- Length
- 6–8 m
- Mass
- 4,800–8,000 kg
- Location
- Montana, Wyoming, Alberta
Quick answers
- How big was Ankylosaurus magniventris?
- Ankylosaurus magniventris was about 6–8 m long. It stood about 1.5–1.8 m tall at the hips. It weighed about 4.8–8 t. (Arbour & Mallon 2017; Paul 2016)
- When did Ankylosaurus magniventris live?
- Ankylosaurus magniventris lived during the Late Cretaceous, about 72.1–66 million years ago. (Cohen et al. 2023; Arbour & Mallon 2017)
- Where have Ankylosaurus magniventris fossils been found?
- Fossils of Ankylosaurus magniventris have been found in Hell Creek Formation (Montana), Lance Formation (Wyoming), and Scollard Formation (Alberta). (Brown 1908; Arbour & Mallon 2017)
- What did Ankylosaurus magniventris eat?
- Ankylosaurus magniventris was a herbivore. (Brown 1908; Arbour & Mallon 2017)
- Who named Ankylosaurus magniventris, and when?
- Ankylosaurus magniventris was described by Barnum Brown in 1908. (Brown 1908)
- Was Ankylosaurus magniventris in Jurassic Park?
- Yes. Ankylosaurus magniventris appears in Jurassic Park III (2001), Jurassic World (2015), Jurassic World: Fallen Kingdom (2018), Jurassic World Dominion (2022), and Jurassic World Rebirth (2025). An armoured tank that swings its tail club, killed by the Indominus rex in Jurassic World. The tail club was a real weapon: models suggest strikes strong enough to break bone. (Wikipedia: Dinosaurs in Jurassic Park 2026; Arbour 2009)
On this page
- Period
- Cretaceous72.1–66 Ma
- Diet
- Herbivore
- Length
- 6–8 m
- Mass
- 4.8–8 t
- Classification
- Ankylosauria · Ankylosauridae
- Described
- 1908, Barnum Brown
Overview
Ankylosaurus magniventris lived in western North America at the end of the Cretaceous, in the same landscapes as Tyrannosaurus and Triceratops. Barnum Brown named it in 1908 from a skull roof and armor found in the Hell Creek Formation of Montana.
It was a low, wide, four-legged plant-eater covered in bony plates (osteoderms) set in the skin, with horns at the back of its skull and a heavy club of fused bone at the end of its tail. It is the largest known ankylosaurid, but it is also known from surprisingly few specimens: no complete skeleton has been found.
Arbour and Mallon (2017) re-examined all the material. They found an unusual nose with looping nasal passages, small leaf-shaped teeth, and estimated a length of roughly 6 to 8 m. The tail club could deliver strong blows, probably against predators or rivals.
Name meaning
From Greek ankylos ("fused, bent") and sauros ("lizard"), for the fused bones of the skull and armor; magniventris, Latin for "great belly" (Brown 1908).
Biology & evidence
What scientists think about how this animal lived, and how strong the evidence for each idea is.
Feeding
Ankylosaurus fed on low plants, cropping them with a wide beak.
Evidence level: Moderate evidenceA low body, a wide muzzle and small leaf-shaped teeth point to a low-level plant-eater. Its diet has not been observed directly.
Skin & covering
Ankylosaurus was covered in bony armor plates set in its skin.
Evidence level: Direct evidenceThe osteoderms themselves are fossilised with the specimens. How exactly they were arranged over the body is reconstructed from better-preserved relatives.
Senses
The looping nasal passages of Ankylosaurus helped it control heat and moisture or produce sounds.
Evidence level: HypothesisThe shape of the nasal passages is known; their function is inferred from similar passages in other ankylosaurs and living animals.
Evidence for / against · 1
Evidence for
Comparative anatomy · Ankylosaurus looping nasal passages
The nostrils face sideways and lead into convoluted nasal passages, unusual among ankylosaurids.
Specimen: CMN 8880
Behavior
Ankylosaurus could swing its tail club hard enough to break bone.
Evidence level: Moderate evidenceModels of ankylosaurid tail clubs show large clubs could hit hard enough to fracture bone. The club of Ankylosaurus is known from one specimen, so its exact force is estimated from relatives.
Evidence for / against · 2
Evidence for
Specimen · Ankylosaurus tail club (AMNH 5214)
A club of large fused osteoderms at the end of a tail stiffened by interlocking vertebrae.
Specimen: AMNH 5214
Biomechanical model · Ankylosaurid tail club impact model
Estimates of the force of tail-club swings in ankylosaurids, large enough to break bone.
Size
- Length
- 6–8 m
- Height
- 1.7 mpublished range 1.5–1.8 m
- Mass
- 4,800–8,000 kg
(26.2 ft)
Based on AMNH 5214 (smallest) to CMN 8880 (largest skull)
(5.6 ft)
Based on AMNH 5214
Timeline
Periods: Maastrichtian (72.1–66 Ma), Late Cretaceous (100.5–66 Ma)
Ages are the ICS 2023/09 bounds of the Maastrichtian, the stage(s) the fossils are assigned to; they bracket the record and are not dated first/last appearances. Known specimens come from the latest Maastrichtian (Hell Creek, Lance, Scollard), so the real range is much narrower, roughly the last 2-3 million years of the Cretaceous.
Location
Formations
- Hell Creek Formation · Montana
- Lance Formation · Wyoming
- Scollard Formation · Alberta
- Gilbert Creek, Hell Creek Formation, Montana · Hell Creek Formation · Montana · position approximate
- Red Deer River, Scollard Formation, Alberta · Scollard Formation · Alberta · position approximate
These are the places where fossils have been found, not the full area where the animal lived.
Ecosystem
Lived in: Hell Creek
68–66 million years ago · floodplain, river system, forest, coastal plain
Warm, humid coastal lowlands and river floodplains west of the retreating Western Interior Seaway at the very end of the Cretaceous, with forests of conifers and flowering plants. The ecosystem ends at the Cretaceous-Paleogene extinction.
Classification
- cladeDinosauria
- cladeOrnithischia
- cladeThyreophora
- cladeAnkylosauria
- familyAnkylosauridae
- subfamilyAnkylosaurinae
- genusAnkylosaurus
- speciesAnkylosaurus magniventris
Taxonomic status: Valid
Fossil record
| Catalog number | Status | Institution | Found |
|---|---|---|---|
| AMNH 5895 | Holotype | American Museum of Natural History (AMNH) | 1906 |
| AMNH 5214 | Referred specimen | American Museum of Natural History (AMNH) | 1910 |
| CMN 8880 | Referred specimen | Canadian Museum of Nature (CMN) | — |
What has been found
Holotype: AMNH 5895
- Preserved
- Partial
- Reconstructed
- Unknown / not recorded
Holotype: AMNH 5895
Region by region (table)
| Region | State |
|---|---|
| Skull | Partial · Skull roof. |
| Mandible | Unknown / not recorded |
| Teeth | Partial |
| Cervical vertebrae | Partial |
| Dorsal vertebrae | Partial |
| Sacrum | Unknown / not recorded |
| Caudal vertebrae | Unknown / not recorded |
| Ribs | Partial |
| Gastralia | Unknown / not recorded |
| Scapula / shoulder girdle | Partial |
| Humerus | Unknown / not recorded |
| Forearm (radius / ulna) | Unknown / not recorded |
| Hand (manus) | Unknown / not recorded |
| Pelvis | Unknown / not recorded |
| Femur | Unknown / not recorded |
| Tibia / fibula | Unknown / not recorded |
| Foot (pes) | Unknown / not recorded |
Referred specimen: AMNH 5214
Region by region (table)
| Region | State |
|---|---|
| Skull | Partial |
| Mandible | Partial |
| Teeth | Unknown / not recorded |
| Cervical vertebrae | Unknown / not recorded |
| Dorsal vertebrae | Unknown / not recorded |
| Sacrum | Unknown / not recorded |
| Caudal vertebrae | Partial · Tail with club. |
| Ribs | Partial |
| Gastralia | Unknown / not recorded |
| Scapula / shoulder girdle | Unknown / not recorded |
| Humerus | Partial |
| Forearm (radius / ulna) | Unknown / not recorded |
| Hand (manus) | Unknown / not recorded |
| Pelvis | Unknown / not recorded |
| Femur | Unknown / not recorded |
| Tibia / fibula | Unknown / not recorded |
| Foot (pes) | Unknown / not recorded |
Referred specimen: CMN 8880
Region by region (table)
| Region | State |
|---|---|
| Skull | Preserved |
| Mandible | Unknown / not recorded |
| Teeth | Unknown / not recorded |
| Cervical vertebrae | Unknown / not recorded |
| Dorsal vertebrae | Unknown / not recorded |
| Sacrum | Unknown / not recorded |
| Caudal vertebrae | Unknown / not recorded |
| Ribs | Unknown / not recorded |
| Gastralia | Unknown / not recorded |
| Scapula / shoulder girdle | Unknown / not recorded |
| Humerus | Unknown / not recorded |
| Forearm (radius / ulna) | Unknown / not recorded |
| Hand (manus) | Unknown / not recorded |
| Pelvis | Unknown / not recorded |
| Femur | Unknown / not recorded |
| Tibia / fibula | Unknown / not recorded |
| Foot (pes) | Unknown / not recorded |
Discovery
- Year described
- 1908
- Described by
- Barnum Brown
- Type specimen
- AMNH 5895
Discovery timeline
1906 · First material found
Barnum Brown collects the Ankylosaurus holotype
Brown collects a partial skull and armor in the Hell Creek Formation of Montana.
People: Barnum Brown
1908 · Formally described
Brown names Ankylosaurus magniventris
Brown names the genus and the family Ankylosauridae.
People: Barnum Brown
1910 · Specimen recovered
Tail club specimen collected in Alberta
Brown collects the specimen with the only known Ankylosaurus tail club.
People: Barnum Brown
2017 · Major study
Arbour and Mallon redescribe Ankylosaurus
A full re-examination of all specimens with new size estimates.
People: Victoria M. Arbour
In Jurassic Park & Jurassic World
Films
- Jurassic Park III (2001)
- Jurassic World (2015)
- Jurassic World: Fallen Kingdom (2018)
- Jurassic World Dominion (2022)
- Jurassic World Rebirth (2025)
On screen
An armoured tank that swings its tail club, killed by the Indominus rex in Jurassic World.
Film vs fossils
- The tail club was a real weapon: models suggest strikes strong enough to break bone.
- Ankylosaurus itself is known from partial skeletons, so much of its body in any reconstruction is borrowed from relatives.
Film titles are used for identification only. DinoDex is not affiliated with or endorsed by the Jurassic Park / Jurassic World franchise. All dinosaurs seen in the films
Sources
- (2026). Wikipedia: Dinosaurs in Jurassic Park. Wikipedia. https://en.wikipedia.org/wiki/Dinosaurs_in_Jurassic_Park (opens in a new tab)
- (2026). Wikipedia: Jurassic World Rebirth. Wikipedia. https://en.wikipedia.org/wiki/Jurassic_World_Rebirth (opens in a new tab)
- Arbour, V. M. (2009). Estimating impact forces of tail club strikes by ankylosaurid dinosaurs. PLoS ONE 4(8): e6738. doi:10.1371/journal.pone.0006738 (opens in a new tab)
- Arbour, V. M. & Mallon, J. C. (2017). Unusual cranial and postcranial anatomy in the archetypal ankylosaur Ankylosaurus magniventris. FACETS 2: 764-794. doi:10.1139/facets-2017-0063 (opens in a new tab)
- Brown, B. (1908). The Ankylosauridae, a new family of armored dinosaurs from the Upper Cretaceous. Bulletin of the American Museum of Natural History 24: 187-201.
- Cohen, K. M., Harper, D. A. T., Gibbard, P. L. & Car, N. (2023). International Chronostratigraphic Chart (v2023/09). International Commission on Stratigraphy. https://stratigraphy.org/ICSchart/ChronostratChart2023-09.pdf (opens in a new tab)
- Paul, G. S. (2016). The Princeton Field Guide to Dinosaurs (2nd edition). Princeton University Press.