''Cyclotosaurus'' is an extinct genus of temnospondyl within the family Mastodonsauridae. It was of great size for an

amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...

, had an elongated skull up to .

Etymology

The name means "round eared lizard" in Ancient Greek, derived from round openings or fenestrae in the cheeks, which are thought to contain structures of the middle ear.

History

German naturalist Eberhard Fraas erected the genus ''Cyclotosaurus'' in 1889, with ''C. robustus'' (previously ''Mastodonsaurus robustus'') as the type species. Several species are known, mainly from Germany and Poland in Central Europe, as well as East Greenland and Thailand. The relationships between species is unclear. ''"Labyrinthodon" pachygnathus'' Owen, 1842 and ''"L." leptognathus'' Owen, 1842 were transferred to ''Cyclotosaurus'', as ''C. pachygnathus'' and ''C. leptognathus'', by Paton (1974). However, Damiani (2001) assigned the two species to Mastodonsauroidea indeterminate and Stereospondyli indeterminate.

Palaeontology

The genus is known from the Ladinian in the Middle Triassic to the

Norian The Norian is a division of the Triassic Period. It has the rank of an age (geochronology) or stage (chronostratigraphy). It lasted from ~227 to million years ago. It was preceded by the Carnian and succeeded by the Rhaetian. Stratigraphic defi ...

in the Late Triassic, and represents the last of the Mastodonsaurids. Restoration of Cyclotosaurus by Szymon Górnicki

The oldest, questionable, species is ''Cyclotosaurus papilio'', known from a partial skull recovered from the Ladinian (Middle Triassic) age Upper Muschelkalk beds from Baden-Württemberg in Germany. ''Cyclotosaurus robustus'' is known from the Carnian ( Late Triassic)

Schilfsandstein Formation The Stuttgart Formation is a geologic formation in Germany. It preserves fossils dating back to the Carnian stage of the Triassic period.Stuttgart-Feuerbach Feuerbach is a borough (''Stadtbezirk'') of the city of Stuttgart. Its name is derived from the small river of the same name that flows from the neighboring district of Botnang through Feuerbach. Feuerbach is home to one of Germany's biggest indu ...

in Germany, while ''C. ebrachensis'' has been described from the

Blasensandstein Formation The Blasensandstein is a Carnian geologic member in Bavaria, Germany. It is part of the Hassberge Formation. Fossil theropod tracks have been reported from the formation.Weishampel et al., 2004, pp.517-607 See also * List of dinosaur-bearing roc ...

Ebrach Ebrach is a municipality with market rights in the Upper Franconian district of Bamberg (district), Bamberg and the seat of the ''Municipal association, Verwaltungsgemeinschaft'' (municipal association) of Ebrach. Geography Ebrach lies between Ba ...

. ''Cyclotosaurus intermedius'' has been described from lacustrine deposits dated to the late Carnian in

Krasiejów Krasiejów (german: Krascheow) is a village in the administrative district of Gmina Ozimek, within Opole County, Opole Voivodeship, in south-western Poland. It lies approximately east of Ozimek and east of the regional capital Opole. The villa ...

in southern Poland. It is so named as it has features intermediate between the more ancient ''C. robustus'' and more recent ''C. mordax''. Importantly, postcranial material of this species has been recovered, which is unusual this genus. ''Cyclotosaurus hemprichi'' is known from the

(Late Triassic) age Knollenmergel of Halberstadt, and ''Cyclotosaurus posthumus'' from the Stubensandstein (Norian) in Pfaffenhofen. A partial skull very similar to ''C. posthumus'' has been recovered from the Norian (Late Triassic) Huai Hin Lat Formation near Chulabhorn Dam in Northeastern Thailand. In 2016 a new species, '' C. buechneri'', was described from the Late Triassic (middle Carnian)

Stuttgart Formation The Stuttgart Formation is a geologic formation in Germany. It preserves fossils dating back to the Carnian stage of the Triassic period.Bielefeld, the northernmost record in Germany. In 2017, ''Cyclotosaurus naraserluki'', a new endemic species from the Fleming Fjord Fm., East Greenland, was described as the closest ''Cyclotosaurus'' species to ''C. mordax'', also being the westernmost and northernmost known species of ''Cyclotosaurus''.Marzola, M., Mateus O., Shubin N. H., & Clemmensen L. B. (2017). Cyclotosaurus naraserluki, sp. nov., a new Late Triassic cyclotosaurid (Amphibia, Temnospondyli) from the Fleming Fjord Formation of the Jameson Land Basin (East Greenland). Journal of Vertebrate Paleontology. e1303501., 2017 In 2019 a ''Cyclotosaurus'' humerus was reported from a Rhaetian aged bone bed within Bonenburg clay pit in eastern North Rhine-Westphalia, Germany. This represents the only definitive non-

brachyopoid Brachyopoidea is a superfamily of temnospondyls that lived during the Mesozoic. It contains the families Brachyopidae and Chigutisauridae. The earliest records of brachyopids are from the Lower Triassic in Australia. The latest-surviving member ...

Rhaetian temnospondyl, and the last known record of Capitosauria.

Phylogeny

The phylogeny of Capitosauroidea according to Witzmann ''et al.'' (2016). The phylogeny of the genus ''Cyclotosaurus'' according to Witzmann et al. (2016). See also alternative phylogenies from 2017 with the description of ''C. naraserluki.''

Ecology

''Cyclotosaurus'' are thought to have been semi-aquatic carnivores, though feeding strategies likely differed between species.

References

{{Taxonbar, from=Q2465083 Triassic temnospondyls of Europe Fossil taxa described in 1889 Prehistoric amphibian genera Taxa named by Eberhard Fraas