Polacanthus
POL-uh-KAN-thus
"many spines"
- Lived
- 137 to 113 million years ago, Early Cretaceous
- Diet
- Herbivore
- Length
- about 5 m (16 ft)
- Group
- Ankylosaurs, Nodosauridae
- Found in
- United Kingdom and Spain
- Named by
- Fox 1866
Size comparison
To scale
Scale in metersOutline: typical ankylosaur shape
Where its fossils were found
The evidence
Today
125 million years ago
Habitat
River plains with seasonal fires in the Wessex Formation supported Iguanodon, Mantellisaurus and Hypsilophodon.
Field notes
About Polacanthus
What it was like
Polacanthus was an armored plant eater about 5 meters (16 feet) long. Rows of tall spines ran along its neck and shoulders, and a solid shield of fused bony plates covered its hips like a saddle.
Its tail carried pairs of flat, sharp-edged plates but no club. Its skull is poorly known.
Its world
It lived about 137 to 113 million years ago, in the Early Cretaceous, in what are now England and Spain. Many of its fossils come from the Wessex Formation of southern England, a land of river plains and seasonal fires.
It shared that land with Iguanodon, Mantellisaurus, Hypsilophodon and the fish-eating Baryonyx.
How it was found
Fox named Polacanthus in 1866. About 13 finds are known. Its closest relative may be Gastonia from North America, and scientists still debate whether the two belong in their own family.
Field gallery
More views of Polacanthus
Scenes reconstructed from the available fossil evidence.
1 of 3
Lived alongside
Found in the same rock formations
A rock formation can hold fossils laid down millions of years apart, so not every animal here met Polacanthus.
The evidence
The science behind Polacanthus
Which parts of the picture come from its own bones, and which come from its relatives.
From its own fossils
- The original skeleton preserves parts of the back, pelvis, tail and hind legs, along with bony armor.
- A broad shield of fused bony plates covered the hips.
- Separate armor pieces include spikes and flattened plates.
Borrowed from relatives
- Gargoyleosaurus helps restore the missing head and front of the body as a low armored quadruped.
Still unknown
- The exact arrangement of its spikes and plates.
- The shape of its complete skull and neck.
- How its armor changed as it grew.
Often drawn wrong
- Its long tail ended without the heavy club of later club-tailed ankylosaurs.
Discovery timeline
- 1866Named itFox
- 2013Close relativeCarpenter et al.
- 2020RedescriptionRaven et al.
Key papers
The research behind what we know of Polacanthus
Named it
Named an armored plant eater from a partial skeleton with spikes and a fused shield over the hips.
On a new Wealden saurian named Polacanthus. Report of the British Association for the Advancement of Science, Birmingham 1865: 56
No link available
Close relative
Compared armored dinosaur pelvises and explained how the broad ankylosaur hips evolved.
Pelvis of Gargoyleosaurus (Dinosauria: Ankylosauria) and the Origin and Evolution of the Ankylosaur Pelvis. PLoS ONE 8: e79887
Read the paper : Pelvis of Gargoyleosaurus (Dinosauria: Ankylosauria) and the Origin and Evolution of the Ankylosaur Pelvis (opens in a new tab)Redescription
Restudied the original Polacanthus and Hylaeosaurus skeletons and reassessed which other armored dinosaur fossils could be assigned to them.
Osteology and Taxonomy of British Wealden Supergroup (Berriasian–aptian) Ankylosaurs (Ornithischia, Ankylosauria). Journal of Vertebrate Paleontology 40: e1826956
Read the paper : Osteology and Taxonomy of British Wealden Supergroup (Berriasian–aptian) Ankylosaurs (Ornithischia, Ankylosauria) (opens in a new tab)
Close relatives
Other members of Nodosauridae
Sources: Wikidata