Procyclotosaurus

{{Short description|Extinct genus of temnospondyls}} {{Automatic taxobox | taxon = Procyclotosaurus | fossil_range = [[Ladinian]],<br />~{{fossil range|241.464|237}}{{period fossil range|Triassic|241.464|237}} | authority = Watson, 1958 | subdivision_ranks = [[Species]] | subdivision = * {{extinct}}'''''P. stantonensis''''' <small>(Woodward, 1904 [originally ''[[Capitosaurus]] stantonensis'') ([[type species|type]])</small> }}

'''''Procyclotosaurus''''' is an extinct [[genus]] of [[Stenotosauridae|stenotosaurid]] [[capitosauria]]n [[temnospondyl]]. The [[type species]] is ''P. stantonensis''. In 1904, [[English people|English]] [[paleontologist]] [[Arthur Smith Woodward]] described it as a species of ''[[Capitosaurus]]'', ''C. stantonensis'', based on a partial skull known as NHMUK PV R 3174. In 1958, the species was assigned to the new genus. It is known from the Lower [[Keuper]], a European stratigraphic unit that was deposited during the [[Ladinian|late Middle Triassic]].<ref>Witzmann, Florian & Sachs, Sven & Nyhuis, Christian. (2016). A new species of Cyclotosaurus (Stereospondyli, Capitosauria) from the Late Triassic of Bielefeld, NW Germany, and the intrarelationships of the genus. Fossil Record. 19. 83-100. 10.5194/fr-19-83-2016. </ref> Fossils have been found from [[Staffordshire]], [[England]].

==Description== ''Procyclotosaurus'' was a relatively small temnospondyl. Unlike most other capitosaurs, which have wide and flat skulls, ''Procyclotosaurus'' has a deep, wedge-shaped skull. The [[otic notch]], a notch at the back of the skull, is closed. The tabular horn above the otic notch is narrow and touches the [[squamosal]] bone below the notch.<ref name=WDMS62>{{cite journal |last=Watson |first=D.M.S. |year=1962 |title=The evolution of the labyrinthodonts |journal=[[Philosophical Transactions of the Royal Society B]] |volume=245 |issue=723 |pages=219–265 |doi=10.1098/rstb.1962.0010|doi-access=free }}</ref> The upper surface of the skull is concave, making it appear dish-shaped. Like other capitosaurs, ''Procyclotosaurus'' resembles [[crocodilian]]s in that it has [[Orbit (anatomy)|orbits]] (eye sockets) and [[nares]] (nostrils) that are directed upward and slightly elevated.<ref name=PRL74>{{cite journal |last=Paton |first=R.L. |year=1974 |title=Capitosauroid labyrinthodonts from the Trias of England |journal=Palaeontology |volume=17 |issue=2 |pages=253–289 |url=http://palaeontology.palass-pubs.org/pdf/Vol%2017/Pages%20253-289.pdf |access-date=2011-01-02 |archive-url=https://web.archive.org/web/20110824004049/http://palaeontology.palass-pubs.org/pdf/Vol%2017/Pages%20253-289.pdf |archive-date=2011-08-24 |url-status=usurped }}</ref>

==History and classification== ''Procyclotosaurus stantonensis'' was first classified as a species of ''Capitosaurus'' and was placed in the family Capitosauridae (now known as [[Mastodonsauridae]]). It was later reassigned as a species of ''[[Cyclotosaurus]]'', another mastodonsaurid genus. In 1958, paleontologist D.M.S. Watson placed the species in its own genus, ''Procyclotosaurus'', distinguishing it from both ''Capitosaurus'' and ''Cyclotosaurus'' on the basis of its deep skull. Watson also found the short suture between the exoccipital and pterygoid bones to be characteristic of the genus. He also noted that ''Procyclotosaurus'' has a crista obliqua, or oblique ridge, on the pterygoid bone at the back of the skull. This ridge is a primitive feature among temnospondyls that is not seen in more [[Synapomorphy|derived]] mastodonsaurids.<ref name=WDMS58>{{cite journal |last=Watson |first=D.M.S |year=1958 |title=A new labyrinthodont (''Paracyclotosaurus'') from the Upper Trias of New South Wales |journal=Bulletin of the British Museum of Natural History |volume=3 |pages=233–264}}</ref>

The holotype of ''Procyclotosaurus'', NHMUK PV R 3174, is thought to be a young adult. The sutures between the bones of the skull are clearly visible and have not fully closed. The skull is pitted and some of the pits have elongated into troughs, a sign of age. However, these troughs are not as prominent as they would be in an older individual. Paleontologist Roberta L. Paton considered the deep skull and close-set eyes of ''Procyclotosaurus'' to be indicative of a young ''Cyclotosaurus'' individual rather than a distinct genus. Therefore, in 1974, Paton reassigned ''Procyclotosaurus stantonensis'' to ''Cyclotosaurus''. Paton also considered ''C. stantonensis'' to be synonymous with the species ''C. leptognathus'', named by English paleontologist [[Richard Owen]], and referred NHMUK PV R 3174 to ''C. leptognathus''.<ref name=PRL74/>

==References== {{Reflist}}

[[Category:Capitosauria]] [[Category:Triassic temnospondyls of Europe]]