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 (16 ft) long. Its body was covered with armour plates and spikes. It possibly was a basal member of the Nodosauridae.
|Hip armour of Polacanthus foxii|
Owen vide Anonymous, 1865 
Owen vide Anonymous, 1865
Polacanthus foxii was discovered by the Reverend William Fox on the Isle of Wight in 1865, at Barnes High at the southwest coast. Fox at first planned to have his friend Alfred Tennyson name the new dinosaur. Tennyson proposed Euacanthus Vectianus but this name was ultimately rejected. In 1865, Fox in a lecture to the British Association reported on the find and let it be named Polacanthus foxii by Richard Owen, hereby circumventing the convention that an author does not name a taxon after himself. The text of the lecture was more or less reproduced by him in an anonymous article in the Illustrated London News. This procedure caused some confusion as no corresponding 1865 publication by Owen exists. Some have therefore contended that Thomas Huxley in 1867 became the author of the name, others give Fox, Owen or "Anonymous" as the author. The generic name is derived from Greek πολύς, polys, "many" and ἄκανθα, akantha, "thorn", in reference to the many spikes of the armour. The specific name honours Fox.
The holotype, BMNH R175, was found in a layer of the Upper Wessex Formation dating from the Barremian. It is an incomplete skeleton with the head, neck, anterior armour and forelimbs missing but including dorsal vertebrae, the sacrum, most of the pelvis, most of the left hindleg, the right thighbone, twenty-two tail vertebrae, ribs, chevrons, ossified tendons, a pelvic shield, twenty-two spikes and numerous ossicles. The skeleton was in 1881 studied by John Whitaker Hulke, while it was still in the possession of Fox. Hulke published the first detailed description of the find, noting that the specimen had badly deteriorated over the years, the dermal armour having almost fully fallen apart. The same year Fox died, his collection was acquired by the British Museum of Natural History, including the Polacanthus fossil. This was then reassembled by preparator Caleb Barlow, painstakingly putting all the pieces together with Canada balsam, much to the wonder of Hulke who in 1881 had called this a hopeless undertaking. This allowed Hulke to redescribe the specimen in 1887, with a special attention to the armour arrangement. In 1905, the specimen was again described by Franz Nopcsa who for the first time provided an illustration of the possible spike configuration.
Later it was realised that, at one occasion at least, even before 1865 probable Polacanthus fossils had been found. In 1843 John Edward Lee reported the discovery on Wight of two armour specimens.
Numerous specimens from Wight and Great Britain have since been referred to Polacanthus. These mostly consist of single bones or armour elements. A second partial skeleton, from which parts had been removed since 1876, was identified and fully excavated by Dr William T. Blows in 1979; it is also in the London Natural History Museum as specimen NHMUK R9293. It is the first specimen to show skull elements, neck vertebrae and unequivocal anterior armour.
Several ankylosaurian remains from the Early Cretaceous of continental Europe have been referred to Polacanthus but none demonstrably share any unique traits, or autapomorphies, with its holotype.
Apart from the two species today considered valid, several other species and genera have been named in relation to the Polacanthus material.
In 1924, Edwin Hennig named a Polacanthus becklesi, the specific name honouring collector Samuel Beckles, based on specimen BMNH R1926, a piece of an ilium associated with armour plates, found on Wight in the nineteenth century. Today this is considered a junior synonym of P. foxii. It was assumed to be a different species because the armour is smoother on top, but this was likely caused by water erosion of the fossil.
In 1987, William T. Blows claimed that the American Hoplitosaurus was a species of Polacanthus, renaming it into Polacanthus marshi. Though this gained some popularity in the early 1990s, today the identity is generally rejected.
In 1996, a Polacanthus rudgwickensis was named by Blows, after a 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, holotype HORSM 1988.1546, is fragmentary and includes several incomplete vertebrae, a partial scapulocoracoid, the distal end of a humerus, a nearly complete right tibia, rib fragments, and two osteoderms. P. rudgwickensis seems to have been about 30% longer than type species P. foxii and differs from it in numerous characters of the vertebrae and dermal armour. 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. In 2015, Blows made it a separate genus Horshamosaurus.
In 1971, Polacanthus foxii was by Walter Coombs renamed into Hylaeosaurus foxi. This has found no acceptance, and the name is an invalid nomen ex dissertatione. Also it has been suggested that Polacanthus would be simply identical to Hylaeosaurus armatus. This was rejected by Blows in 1987, because of differences in age and anatomy. A possible identity is hard to prove or disprove as there are few overlapping elements in their holotypes.
In 1928, Nopcsa named a new genus and species Polacanthoides ponderosus, based on a number of syntypes: BMNH 2584, a left scapula found at Bolney which in 1841 by Gideon Mantell had been referred to Hylaeosaurus; and BMNH R1106 en 1107, a tibia and humerus. The new taxon has proven to be very problematic. Contrary to what Nopcsa assumed the tibia and humerus were not found at Bolney but on Wight. This makes Polacanthoides a possible chimaera, especially since their provenance from Wight makes it likely they belonged to Polacanthus. Furthermore, the Wight specimens are not the original bones, which have been lost, but casts which at best could have been used as plastotypes. The scapula belongs to an indeterminate thyreophoran.
In 1982 Justin Delair named a genus Vectensia, without providing a specific name, based on specimen GH 981.45, an armour plate. Like the holotype of Polacanthus it was found at Barnes High, but reportedly in an older layer, of the Lower Wessex Formation. Blows in 1987 tentatively referred it to Polacanthus.
Polacanthus was a medium-sized ankylosaur. In 2010, Gregory S. Paul estimated its length at five metres, its weight at two tonnes. Its hindlimbs are relatively long for an ankylosaur, with a right femur length of 555 millimetres with the holotype.
In 2011 Barrett e.a. indicated two possible unique traits, autapomorphies: the floor of the neural canal is deeply cut by a groove with a V-shaped transverse profile; the caudal spikes have triangular bases in side view and narrow points.
The subsequent describers have always dedicated much effort at restoring the armour configuration. Hulke understood that Polacanthus had a large "pelvic shield" or "sacral shield", a single fused sheet of dermal bone over its hips (sacral area) which perhaps was not attached to the underlying bone and decorated with tubercles. This feature is shared with other "polacanthine" (basal nodosaurids) dinosaurs such as Gastonia and Mymoorapelta. With the holotype, this shield is 108 centimetres wide and 90 centimetres long. It features four horizontal rows of larger keeled osteoderms per side, surrounded by smaller ossicles. These latter are sometimes completely fused to form flat armour plates. Hulke thought that on the tail there were two rows of keeled osteoderms per side. Of a set of spikes found with the fossil, he assumed they had adorned the sides of the rump. A different arrangement was hypothesised by Nopcsa. He thought that both the tail and the front of the body including the neck featured two parallel rows of spikes, one per side. On the front body each row would have consisted of five spikes and he claimed that seven of these had been conserved with the fossil, five of the right side and two of the left. The tail rows would have consisted of twenty-two shorter pairs, fifteen spikes being still extant, eight of the left side and seven of the right. As the spikes are asymmetrical their position can more or less be deduced. Blows in 1987 basically agreed with Nopcsa but also distinguished three spike types, a Type A, B and C, allowing him to classify additional fossil finds, which often differed from the holotype spikes in several details.
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.
Paleontology or palaeontology (from Greek: paleo, "ancient"; ontos, "being"; and logos, "knowledge") is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1865.Ankylosaurinae
Ankylosaurinae is a subfamily of ankylosaurid dinosaurs, existing from the Early Cretaceous about 105 million years ago until the end of the Late Cretaceous, about 66 mya. Many genera are included in the clade, such as Ankylosaurus, Pinacosaurus, Euoplocephalus, and Saichania.Anoplosaurus
Anoplosaurus (meaning "unarmored or unarmed lizard") is an extinct genus of herbivorous nodosaurid dinosaur, from the late Albian-age Lower Cretaceous Cambridge Greensand of Cambridgeshire, England. It has in the past been classified with either the armored dinosaurs or the ornithopods, but current thought has been in agreement with the "armored dinosaur" interpretation, placing it in the Ankylosauria.Barremian
The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch (or Lower Cretaceous series). It is preceded by the Hauterivian and followed by the Aptian stage.Dinosaur Isle
Dinosaur Isle is a purpose-built dinosaur museum located in Sandown on the Isle of Wight in southern England.The museum was designed by Isle of Wight architects Rainey Petrie Johns in the shape of a giant pterosaur. It claims to be the first custom-built dinosaur museum in Europe.Dongyangopelta
Dongyangopelta is an extinct genus of nodosaurid ankylosaurian dinosaur known from the "middle" Cretaceous Chaochuan Formation (Albian or Cenomanian stage) of Dongyang, Zhejiang Province, China. Dongyangopelta was first named by Rongjun Chen, Wenjie Zheng, Yoichi Azuma, Masateru Shibata, Tianliang Lou, Qiang Jin and Xingsheng Jin in 2013 and the type species is Dongyangopelta yangyanensis. It differs from Zhejiangosaurus, the second nodosaurid from southeast China, in the characters of presacral rod, ilium, and femur. Donyangopelta is distinguishable from Zhejiangosaurus only on the basis of the morphology of its pelvic shield.Gastonia (dinosaur)
Gastonia is a genus of herbivorous ankylosaurian dinosaur from the Early Cretaceous of North America, around 125 million years ago. It is often considered a nodosaurid closely related to Polacanthus. Gastonia has a sacral shield and large shoulder spikes.Hoplitosaurus
Hoplitosaurus (meaning "Hoplite lizard") was a genus of armored dinosaur related to Polacanthus. It was named from a partial skeleton found in the ?Barremian-age Lower Cretaceous Lakota Formation of Custer County, South Dakota. It is an obscure genus which has been subject to some misinterpretation of its damaged remains. Although there was a push to synonymize it with Polacanthus in the late 1980s-early 1990s, Hoplitosaurus has been accepted as a valid albeit poorly known genus in more recent reviews.Horshamosaurus
Horshamosaurus is a genus of herbivorous ankylosaurian dinosaur from the Early Cretaceous of England.Hylaeosaurus
Hylaeosaurus ( hy-LEE-o-SOR-əs; Greek: hylaios/ὑλαῖος "belonging to the forest" and sauros/σαυρος "lizard") is a herbivorous ankylosaurian dinosaur that lived about 136 million years ago, in the late Valanginian stage of the early Cretaceous period of England.
Hylaeosaurus was one of the first dinosaurs to be discovered, in 1832 by Gideon Mantell. In 1842 it was one of the three dinosaurs Richard Owen based the Dinosauria on. Four species were named in the genus, but only the type species Hylaeosaurus armatus is today considered valid. Only limited remains have been found of Hylaeosaurus and much of its anatomy is unknown. It might have been a basal nodosaurid, although a recent cladistic analysis recovers it as a basal ankylosaurid.Hylaeosaurus was about five metres long. It was an armoured dinosaur. It carried at least three long spines on its shoulder.Martin I. Simpson
Martin I. Simpson is a British palaeontologist, a geologist best known for his work in the Whitby area. He lives on the Isle of Wight and runs Island Gems at Isle of Wight pearl. Though perhaps best known for his appearances in the British news media, he is also an established expert on Cretaceous fossil crustaceans and has produced important papers on the Cretaceous Lower Greensand Group. His proposal that the five units of the Atherfield Clay Formation be formally recognised as local members has been widely adopted. He has produced a popular book on fossil hunting, titled Fossil Hunting on Dinosaur Island, and was heavily involved in the excavation of a significant specimen of the ankylosaur Polacanthus.He has also written about the trade in fossils and on the relationship between academic palaeontologists and amateur dealers and collectors. In the BBC TV series Life from Dinosaur Island Simpson was associated with the discovery of Isle of Wight amber.Nodosauridae
Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous period of what are now North America, Europe, Asia, Africa, and Antarctica.Polacanthinae
Polacanthinae is a grouping of ankylosaurs, possibly primitive nodosaurids. Polacanthines are late Jurassic to early Cretaceous in age, and appear to have become extinct about the same time a land bridge opened between Asia and North America.Polacanthines were somewhat more lightly armoured than more advanced ankylosaurids and nodosaurids. Their spikes were made up of thin, compact bone with less reinforcing collagen than in the heavily armoured nodosaurids. The relative fragility of polacanthine armour suggests that it may have been as much for display as defense.Polacanthoides
Polacanthoides (meaning Polacanthus like) is an extinct genus of nodosaurid dinosaur from Europe. It lived about 140 to 135 million years ago in what is now England. It was named by Nopsca in 1928. The type specimen is BMNH 2584. It is a possible junior synonym of Hylaeosaurus and Polacanthus. It is now considered to be a nomen dubium or a chimera.Sarcolestes
Sarcolestes (meaning "flesh robber") is an extinct genus of ankylosaurian ornithischian dinosaur from the Oxford Clay of England. The current type and only species is S. leedsi, and the holotype is a single partial left mandible. The genus and species were named in 1893 by Richard Lydekker, who thought they belonged to a theropod.Taohelong
Taohelong is a genus of nodosaurid dinosaur known from Lower Cretaceous rocks in north-central China.
Taohelong is based on Gansu Dinosaur Museum (GSDM) 00021, fossils including a tail vertebra, ribs, a left ilium (the main bone of the hip), and bony armor recovered from the Hekou Group in the Lanzhou-Minhe Basin. The animal's armor includes part of a "sacral shield", a carpet of osteoderms over the hips found in some other ankylosaurians. Taohelong was named and described in 2013 by Yang Jing-Tao, You Hai-Lu, Li Da-Qing, and Kong De-Lai. The type species is Taohelong jinchengensis. The generic name means "dragon (long) of the river (he) Tao". The specific name refers to the provenance at Jincheng.The describers established some diagnostic traits. The neural channel of the tail vertebra has a cross-section like an inverted trapezium. In top view the profile of the outer rim of the ilium is like a mirrored "S". The osteoderms of the sacral shield are irregular in both shape and size.Taohelong was placed in the Nodosauridae, more precisely in the Polacanthinae. Yang et al. performed a phylogenetic analysis and found Taohelong to be the sister taxon to Polacanthus foxii, making it the first polacanthine to be described from Asia.Tatisaurus
Tatisaurus is a genus of ornithischian dinosaur from the Early Jurassic from the Lower Lufeng Formation in Yunnan Province in China. Little is known as the remains are fragmentary.Timeline of ankylosaur research
This timeline of ankylosaur research is a chronological listing of events in the history of paleontology focused on the ankylosaurs, quadrupedal herbivorous dinosaurs who were protected by a covering bony plates and spikes and sometimes by a clubbed tail. Although formally trained scientists did not begin documenting ankylosaur fossils until the early 19th century, Native Americans had a long history of contact with these remains, which were generally interpreted through a mythological lens. The Delaware people have stories about smoking the bones of ancient monsters in a magic ritual to have wishes granted and ankylosaur fossils are among the local fossils that may have been used like this. The Native Americans of the modern southwestern United States tell stories about an armored monster named Yeitso that may have been influenced by local ankylosaur fossils. Likewise, ankylosaur remains are among the dinosaur bones found along the Red Deer River of Alberta, Canada where the Piegan people believe that the Grandfather of the Buffalo once lived.The first scientifically documented ankylosaur remains were recovered from Early Cretaceous rocks in England and named Hylaeosaurus armatus by Gideon Mantell in 1833. However, the Ankylosauria itself would not be named until Henry Fairfield Osborn did so in 1923 nearly a hundred years later. Prior to this, the ankylosaurs had been considered members of the Stegosauria, which included all armored dinosaurs when Othniel Charles Marsh named the group in 1877. It was not until 1927 that Alfred Sherwood Romer implemented the modern use of the name Stegosauria as specifically pertaining to the plate-backed and spike-tailed dinosaurs of the Jurassic that form the ankylosaurs' nearest relatives. The next major revision to ankylosaur taxonomy would not come until Walter Coombs divided the group into the two main families paleontologists still recognize today; the nodosaurids and ankylosaurids. Since then, many new ankylosaur genera and species have been discovered from all over the world and continue to come to light. Many fossil ankylosaur trackways have also been recognized.William Fox (palaeontologist)
William D. Fox (9 August 1813 – 1881) was an English clergyman and palaeontologist who worked on the Isle of Wight and made some significant discoveries of dinosaur fossils.
The Reverend William D. Fox was born in Cumberland. He moved to the Isle of Wight in 1862 to take up the post of curate at the Parish church of St Mary the Virgin in Brixton (now known as Brighstone). He resigned his post in 1867 but continued to live in the area to carry on his collecting. In 1875, he became curate of nearby Kingston, near Shorwell.Although lacking formal scientific training Fox was remarkably astute and discussed his findings with eminent palaeontologists of the day including John Hulke (1830-1895) and Sir Richard Owen. Fox had easy access to Brighstone Bay from his home, Myrtle Cottage in Brighstone, and so spent many an hour collecting fossils, much to the detriment of his pastoral work; in fact, it was said of him at the time, by the wife of the vicar, that it was "always bones first and the parish next". He is also quoted as having written in a letter to Owen "I cannot leave this place while I have any money left to live on, I take such deep [sic] in hunting for old dragons".In 1882 Fox's collection of more than 500 specimens was acquired by the Natural History Museum after his death.Fox is credited with the finding of several species, most described by his friend Owen, and named by him after their finder. These include Polacanthus foxii, Hypsilophodon foxii, Eucamerotus foxi, Iguanodon foxii, Calamosaurus foxii (formerly Calamospondylus) and Aristosuchus.