Polacanthus
Name:
Polacanthus
(Many Spikes).
Phonetic: Po-la-can-thuss.
Named By: Richard Owen - 1865.
Synonyms: Euacanthus.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Thyreophora, Ankylosauria, Ankylosauridae,
Polacanthinae.
Species: P. foxii (type).
Type: Herbivore.
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.
Discovered
by Reverend William D. Fox in 1865, Polacanthus
has been
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.
Further reading
- 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.
- Espinas dermicas del dinosaurio anquilosaurio Polacanthus en las
facies Weald de Salas de Los Infantes (Burgos, Espa�a). - Estudios
Geol�gicos 55: 267-272. - X. Pereda-Suberbiola, M. Meijide, F. Torcida,
J. Welle. C. Fuentes, L. A. Izquierdo, D. Montero, G. P�rez &
V. Uri�n - 1999.
- New remains of the ankylosaurian dinosaur Polacanthus
from the Lower
Cretaceous of Soria, Spain. - Cretaceous Research 28: 583–596. - X.
Pereda-Suberbiola, C. Fuentes, M. Meijide, F. Meijide-Fuentes &
M.J. Meijide-Fuentes - 2007.
- Wealden armoured dinosaurs, by P. M. Barrett & S. C. R.
Maidment. In English Wealden fossils. Palaeontological Association,
London, Field Guides to Fossils 14, 769 pp, D. J. Batten (ed). - 2011.
- Elementos de la armadura dermica del dinosaurio anquillosaurio
Polacanthus Owen, 1865, en al Cret�cico inferior de
Morella (Castell�n,
Espa�a). - Ameghiniana 48(4): 508-519. - J. M. Gasulla, F. Oretga, X.
Pereda-Suberbiola, F. Escaso & J. L. Sanz - 2011.
- First Valanginian Polacanthus foxii (Dinosauria,
Ankylosauria) from
England, from the Lower Cretaceous of Bexhill, Sussex. - Proceedings of
the Geologists' Association 125: 233–251. - William T. Blows &
Kerri Honeysett - 2014.
- Osteology and Taxonomy of British Wealden Supergroup
(Berriasian–Aptian) Ankylosaurs (Ornithischia, Ankylosauria) - Journal
of Vertebrate Paleontology, DOI: 10.1080/02724634.2020.1826956. -
Thomas J. Raven, Paul M. Barrett, Stuart B. Pond & Susannah C.
R. Maidment - 2020.
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