Named By: Richard Owen - 1865.
Classification: Chordata, Reptilia, Dinosauria, Ornithischia, Thyreophora, Ankylosauria, Ankylosauridae, Polacanthinae.
Species: P. foxii (type), P. rudgwickensis.
Size: 4 meters long.
Known locations: United Kingdom, Isle of Wight, Sussex.
Time period: Barremian of the Cretaceous.
Fossil representation: Several specimens of individuals, but only the rear has been well preserved.
by Reverend William D. Fox in 1865, Polacanthus
frustratingly ill preserved with only the hind quarters and parts of
armour well preserved. The skull is also unknown, and for this
reason modern reconstructions are based upon comparisons with other
similar dinosaurs like Gastonia.
What can be ascertained is that Polacanthus was a quadrupedal low browser with heavy armour adaptations along its back. These include spikes over much of its body and a huge 'shield' that covered its hips and sacrum. This shield was built up from a mass of osteoderms and was not connected to any bone structure underneath. It could be that the armour was primarily for defence against theropods like Neovenator and Eotyrannus, which would have only been able to bite down from above.
The spikes would've made it difficult to get close without a carnivore impaling its snout, and the sacral armour prevented a bite to the sacrum that could have paralysed Polacanthus. If the tail was also a defensive weapon, the sacral armour would have helped to prevent a predator from disabling its defence.
- On a new Wealden saurian named Polacanthus - W. Fox - 1865.
- Polacanthus foxii, a large undescribed dinosaur from the Wealden Formation in the Isle of Wight - J. W. Hulke - 1881.
- The armoured dinosaur Polacanthus foxi, from the Lower Cretaceous of the Isle of Wight - W. T. Blows - 1987.
- A new species of Polacanthus (Ornithischia; Ankylosauria) from the Lower Cretaceous of Sussex, England - W. T. Blows - 1996.