Polacanthus

From Wikipedia, the free encyclopedia

iPolacanthus
Fossil range: Early Cretaceous

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Superorder:	Dinosauria
Order:	Ornithischia
Suborder:	Thyreophora
Infraorder:	Ankylosauria
Family:	Ankylosauriddae
Subfamily:	Polacanthinae
Genus:	Polacanthus Owen, 1865

Polacanthus, deriving its name from the Ancient Greek poly-/πολυ- "many" and acantha/ακανθα "thorn" or "prickle"^[1], was an early armored, spiked, plant-eating ankylosaur from the early Cretaceous period. It lived 132 to 112 million years ago in what is now western Europe.

1 Description
2 Discovery and species
3 Popular Culture
4 References
5 External links

[edit] Description

Polacanthus grew to between 4 and 5 meters long. It was a quadrupedal ornithischian or "bird-hipped" dinosaur. There are not many fossil remains of this creature, and some important anatomical features, such as its skull, are poorly known.

Polacanthus had a large sacral shield, a single fused sheet of dermal bone over its hips (sacral area) which was not attached to the underlying bone and decorated with tubercles. This feature is shared with other Polacanthine dinosaurs such as Gastonia and Mymoorapelta.

[edit] Discovery and species

The genus Polacanthus comprises two species from Europe, with a possible third from the Lower Cretaceous of North America. However, this latter species has been placed by some into a separate genus and is alternately known as Hoplitosaurus marshi.

Polacanthus foxii was discovered by the Reverend William Fox on the Isle of Wight in 1865^[2] and named by Sir Richard Owen the same year. It was an incomplete skeleton with the head, neck, anterior armour and forelimbs missing. Two other partial skeletons have since been found. The second known specimen was found and excavated by Dr William T. Blows in 1979, and is also in the London Natural History Museum. It is the first specimen to show neck vertebrae and anterior armour^[3].

P. rudgwickensis was named in 1996 by Dr. William T. Blows^[4], after review of some fossil material found in 1985 and thought to have been Iguanodon, which was on display at the Horsham Museum in Sussex. The material is fragmentary and includes several incomplete vertebrae, partial scapulocoracoid, the distal end of humerus, a nearly complete right tibia, rib fragments, and two osteoderms. P. rudgwickensis seems to have been about 30% larger than type species P. foxii and differs from it in numerous characters of the vertebrae and dermal armor. It is named after the village of Rudgwick in West Sussex and was discovered at a Rudgwick Brickworks Company quarry, at the quarry floor in gray-green marl beds of the Wessex Formation. Barremian age, approximately 124-132 million years ago.

[edit] Popular Culture

Outdated restoration of Polacanthus.

Despite its dramatic appearance, Polacanthus is not often depicted in popular culture. However, it did appear on the fourth episode of Walking with Dinosaurs, but only for a brief time. It and Iguanodon are said to travel together.

Early depictions often gave it a very vague head as it was only known from the rear half of the creature.

Polacanthus bones can be seen in Bexhill museum in East Sussex, and Horsham museum in West Sussex.

[edit] References

^ Liddell & Scott (1980). Greek-English Lexicon, Abridged Edition. Oxford University Press, Oxford, UK. ISBN 0-19-910207-4.
^ Fox W. (1865). On a new Wealden saurian named Polacanthus. Report of the British Association for the Advancement of Science, 1865 for 1864, p. 56
^ Blows WT. (1987). The armoured dinosaur Polacanthus foxi, from the Lower Cretaceous of the Isle of Wight, Palaeontology. 30, 557–580
^ Blows WT (1996) A new species of Polacanthus (Ornithischia; Ankylosauria) from the Lower Cretaceous of Sussex, England. Geological Magazine, 133 (6): 671-682

Blows WT (2001). “Dermal Armor of Polacanthine Dinosaurs”, Carpenter, Kenneth(ed) The Armored Dinosaurs. Indiana University Press, 363–385. ISBN 0-253-33964-2.

Carpenter K (2001). “Phylogenetic analysis of the Ankylosauria”, Carpenter, Kenneth(ed) The Armored Dinosaurs. Indiana University Press, 455–484. ISBN 0-253-33964-2.