page_title: Polacanthus
section_title: Phylogeny
hierarchical_section_title: Polacanthus / Phylogeny
caption_attribution_description: PLATE 73. Fig. 1. Lateral view of a fragment of the tail, sheathed by haemal and neural keeled scutes, between which are the remains of a lateral series of small peltate scute tubercles. The vertebral centra, c.c'., are overlaid by bundles of ossified tendons, t. Fig. 2. Sectional view of the fractured surface at c'. c. Crushed centrum. hh Hoemal and neural scutes. Fig. 3. Foreshortened view of scute at x. b, marks the same border in. this and in fig. 1. Fig. 4. Lateral view of a large keeled scute with angularly excavated base.
context_page_description: Polacanthus, deriving its name from the Ancient Greek polys-/πολύς- "many" and akantha/ἄκανθα "thorn" or "prickle", is an early armoured, spiked, plant-eating ankylosaurian dinosaur from the early Cretaceous period of England.
  In the genus Polacanthus several species have been named but only the type species Polacanthus foxii is today seen as valid.
  Polacanthus was a quadrupedal ornithischian or "bird-hipped" dinosaur. It lived 130 to 125 million years ago in what is now western Europe. Polacanthus foxii was named after a find on the Isle of Wight in 1865. There are not many fossil remains of this creature, and some important anatomical features, such as its skull, are poorly known. Early depictions often gave it a very generic head as it was only known from the rear half of the creature. It grew to about 5 metres long. Its body was covered with armour plates and spikes. It possibly was a basal member of the Nodosauridae.
context_section_description: Fox in 1865 assigned Polacanthus to the Dinosauria, Huxley in 1870 and Hulke in 1881 assigned it to the Scelidosauridae. Its exact affinities were not well understood, until Coombs in 1978 placed in the Nodosauridae within a larger Ankylosauria. In 1996 Kenneth Carpenter e.a. refined this to the Polacanthinae. An alternative hypothesis, first suggested by Tracy Lee Ford in 2000, is that there existed a clade Polacanthidae below the Nodosauridae + Ankylosauridae node.
  A more conventional analysis from 2012, in which Polacanthos foxii and P. rudgwickensis were not recovered as sister species, is shown by this cladogram:
caption: Tail, centrum, and scute fragments
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