| Camelotia | |
|---|---|
 | |
| Holotype femur ofCamelotia borealis (NHMUK R2870) | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Family: | †Melanorosauridae |
| Genus: | †Camelotia Galton, 1985 |
| Species: | †C. borealis |
| Binomial name | |
| †Camelotia borealis | |
Camelotia (meaning "fromCamelot") is a large-bodiedsauropodomorph from the latestTriassic (Rhaetian) of southwestEngland. It is best known from a partial postcranial skeleton found in theWestbury Formation and named by Peter M. Galton in 1985. Subsequent work has generally placedCamelotia as a relativelyderived sauropodomorph close to the origin ofSauropoda, although its exact position among early non-sauropod sauropodomorphs remains debated. It is sometimes placed inMelanorosauridae as a close relative ofMelanorosaurus. With a body length and mass estimated at 8–10 metres (26–33 ft) and 3.8 tonnes (8,400 lb), respectively, it is one of the largest sauropodomorphs known from the Triassic.
The first discovery of a large dinosaur in theTriassic of England was in1894 in the parish ofWedmore, where quarrying to the south-east of the village exposed multiple large fragments brought to the attention ofWilliam Ayshford Sanford by his brother-in-law Sydenham Henry Augustus Hervey. Sanford and Hervey collected multiple bones themselves, and from the cottages of the quarry workmen, and Sanford cleaned and prepared them to compare with other dinosaurs. Taking the bones, including partial limbs and other elements, to theNatural History Museum, London for comparison, he would they bore enough resemblance to those ofMegalosaurus to conclude that a very large megalosaur was present in theMendip Hills during the Triassic. However, despite their clear difference from other known taxa, Sanford declined to name them and instead gave them to the NHMUK to be studied by palaeontologistHarry Govier Seeley.[2]
Seeley published his description of the numerous specimens in1898. From the collection included two teeth, multiple bones of thehindlimb and foot,dorsal andcaudal vertebrae, and ribs. The condition of the bones was imperfect, with them found crushed and scattered by a combination of transport before burial and geologic changes since burial. The first tooth, which he incorrectly noted as found within the jaw, he namedAvalonia sanfordi, while the second tooth, the one actually found within a partial jaw that immediately crumbled into mud when exposed, he namedPicrodon herveyi.[3][4] ToAvalonia he also assigned thefemur and other parts of the hindlimb, while the dorsal vertebrae were referred to either the largerAvalonia or smallerPicrodon based on their size. Seeley consideredAvalonia a closer relative ofZanclodon andPicrodon a closer relative ofMegalosaurus, though both were still related megalosaurs.[3] As the genus nameAvalonia was preoccupied by atrilobite named in 1889, the dinosaur was renamedAvalonianus byOskar Kuhn in1961.[5]
Avalonianus was considered a synonym ofGresslyosaurus by German palaeontologistFriedrich von Huene in 1908 and again in 1932, and then retained as a separate member of theprosauropod familyMelanorosauridae by British palaeontologistAlan J. Charig and colleagues in 1965. Though a melanorosaurid identity ofAvalonianus was supported by further studies, it was also consideredundiagnostic by some as the tooth it was founded upon cannot be distinguished from other taxa. The association of carnivorous teeth like those ofAvalonianus with postcranial skeletons of prosauropods was disputed by British palaeontologistPeter M. Galton, who instead considered the teeth to be signs of predation, rather than prosauropods being carnivorous. As a result, in1985 he removed the postcranial material ofAvalonianus andPicrodon to the new taxonCamelotia borealis, leaving only the carnivorous teeth in the former genera. Theholotype ofCamelotia was indicated to be a series of specimens in the NHMUK Galton believed to belong to a single individual; four dorsal vertebrae, five caudal vertebrae, rib andchevron fragments, apubis, anischium, a femur, a partialtibia, and twophalanges from the foot under the specimen numbers NHMUK R2870-2874 and R2876-2878. Thegeneric name chosen was derived fromCamelot, the legendary seat ofKing Arthur that was probably inSomerset, while thespecific name was from theLatin for "north", asCamelotia borealis was the only melanorosaurid from the northern hemisphere known at the time.[1]
All the dinosaur remains from Wedmore came from a single small quarry in the vale ofGlastonbury, referred to "Rhaetic" beds that correlate with only a portion of theRhaetian stage of the Late Triassic. To avoid this confusion, the "Rhaetic beds" were given the formal name of thePenarth Group in 1980 by Warrington and colleagues, consisting of a youngerLilstock Formation and an olderWestbury Formation. The Wedmore Stone from whichCamelotia is known is a locallimestone near the base of the Westbury Formation in the region of Wedmore. While it was extensively worked in shallow quarries, the Wedmore Stone is only around 1 m (3.3 ft) thick, and so by 1911 even traces of the former quarries were difficult to locate.[4] Other dinosaur remains have also been found in the Rhaetic Bone Beds of the Westbury Formation ofAust Cliff, and while they are not diagnostic it is possible that they belong toCamelotia based on size.[6][7]
Although incompletely known,Camelotia was a robust, large-bodied sauropodomorph. The femur is ~1 metre (3 ft 3 in) long (in the holotype), indicating an animal roughly on the order of 8–10 metres (26–33 ft) in length based on comparative scaling to closely related basal sauropodomorphs.[4] Its body mass has been estimated at 3.8 tonnes (8,400 lb).[8] The dentition known from associated material in the same beds is of serrated, leaf-shaped crowns typical of herbivorous sauropodomorphs.[4] Limb and girdle proportions in early near-sauropods suggest increasing forelimb robustness and a trend toward habitual quadrupedality by the earliest Jurassic, butCamelotia itself remains too incomplete for a confident locomotor reconstruction.[9][8] However, phylogenetic analysis suggests thatCamelotia is nested within advanced sauropodomorphs close to Sauropoda that had adopted quadrupedality.[8]
Camelotia has historically been allied to "prosauropods" (now recognized as a paraphyletic grade). Most recent treatments place it close to Melanorosauridae or as a basal sauropodiform taxon just outside Sauropoda; some analyses consider it potentially a basal sauropod.[4][9] Because the holotype is fragmentary, its precise placement depends on character sampling across early sauropodomorph matrices, and remains provisional pending new material or re-study.[8] Some phylogenies have recovered it as part of the familyMelanorosauridae as a close relative ofMelanorosaurus from the Late Triassic of South Africa, though other phylogenies have found them to be unrelated.[10][8][11] The cladogram below shows the relationships ofCamelotia and other members ofAnchisauria relative to true sauropods as found by André Fonseca and colleagues.[12]
Probable large sauropodomorph trackways exposed on the shoreline nearPenarth, South Wales assigned to theichnogenusEosauropus may have been produced byCamelotia, but this uncertain.[13]
Other dinosaurs known from thePenarth Group (of which the Westbury Formation is part) include the large theropodNewtonsaurus cambrensis. Theropod teeth associated with the holotypeCamelotia skeleton which were historically assigned toAvalonianus, were suggested by Galton in 1998 to represent the same species asNewtonsaurus cambrensis.[4] Dinosaurs known from Late Triassic fissure fill deposits in the South Wales-South West England region include the sauropodomorphsPantydraco,Thecodontosaurus, and the coelophysoid theropodPendraig, as well as other vertebrates such asprocolophonid,rhynchocephalian, andcrocodylomorph reptiles, and earlymammaliamorphs (mammal-linecynodonts) liketritylodontids andmorganucodonts,[14][15] but it is disputed whether these fissure fills are Rhaetian in age or contain considerably older fossils dating to theCarnian-Norian.[16][15]
