# Ankylosaurus magniventris

> 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.

- Classification: Dinosauria (clade) > Ornithischia (clade) > Thyreophora (clade) > Ankylosauria (clade) > Ankylosauridae (family) > Ankylosaurinae (subfamily) > Ankylosaurus (genus) > Ankylosaurus magniventris (species)
- Length: 6–8 m
- Hip height: 1.5–1.8 m
- Mass: 4.8–8 t
- Age: 72.1–66 million years ago (Late Cretaceous)
- Fossils found in: Hell Creek Formation (Montana); Lance Formation (Wyoming); Scollard Formation (Alberta)
- Diet: herbivore
- Described: Barnum Brown, 1908
- In films: Jurassic Park III (2001), Jurassic World (2015), Jurassic World: Fallen Kingdom (2018), Jurassic World Dominion (2022), Jurassic World Rebirth (2025)

Canonical page: https://dinodex.club/dinosaurs/ankylosaurus-magniventris
Last updated: 2026-09-27

## 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).

## Sources

1. Arbour, V. M. (2009). Estimating impact forces of tail club strikes by ankylosaurid dinosaurs. PLoS ONE 4(8): e6738. https://doi.org/10.1371/journal.pone.0006738
2. Arbour, V. M. & Mallon, J. C. (2017). Unusual cranial and postcranial anatomy in the archetypal ankylosaur Ankylosaurus magniventris. FACETS 2: 764-794. https://doi.org/10.1139/facets-2017-0063
3. 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.
4. 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
5. Paul, G. S. (2016). The Princeton Field Guide to Dinosaurs (2nd edition). Princeton University Press.

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Cite as: "Ankylosaurus magniventris". DinoDex. https://dinodex.club/dinosaurs/ankylosaurus-magniventris (updated 2026-09-27).