Cyclotosaurus

Cyclotosaurus
Temporal range: Late Triassic
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: †Temnospondyli
Superfamily: Capitosauroidea
Family: Mastodonsauridae
Genus: Cyclotosaurus
Fraas, 1889
Species
  • C. robustus (Quenstedt, 1850) (type)
  • C. posthumus Fraas, 1913
  • C. papilio Wepfer, 1923
  • C. ebrachensis Kuhn, 1932
  • C. hemprichi Kuhn, 1942

Cyclotosaurus is an extinct genus of temnospondyl within the family Mastodonsauridae. It was of great size for an amphibian, reaching 3–4.3 m (9–14 ft) in length with an elongated 70 cm (28 in) skull.[1][2]

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.[3]

History

Cyclotosaurus mordax skull

German naturalist Eberhard Fraas erected the genus Cyclotosaurus in 1889, with C. robustus (previously Mastodonsaurus robustus) as the type species.[4] Several species are known, mainly from Germany and Poland in Central Europe, as well as East Greenland and Thailand.[5][6] The relationships between species is unclear.[7] The English zoologist Richard Owen described a species "Labyrinthodon pachygnathus" (Cyclotosaurus pachygnathus) of uncertain affinity in 1842.[8]

Palaeontology

Cyclotosaurus intermedius model

The genus is known from the Ladinian in the Middle Triassic to the Norian in the Late Triassic, and represents the last of the Mastodonsaurids.[4]

The oldest species is Cyclotosaurus papilio, known from a partial skull recovered from the Ladinian (Middle Triassic) age Upper Muschelkalk beds from Baden-Württemberg in Germany.[4] Cyclotosaurus robustus is known from the Carnian (Late Triassic) Schilfsandstein Formation in Stuttgart-Feuerbach in Germany, while C. ebrachensis has been described from the Blasensandstein Formation in Ebrach.[9] Cyclotosaurus intermedius has been described from lacustrine deposits dated to the late Carnian in Krasiejów 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.[7] Cyclotosaurus carinidens is known from the Norian (Late Triassic) age Knollenmergel of Halberstadt, and Cyclotosaurus posthumus from the Stubensandstein Formation (Norian) in Pfaffenhofen.[9] 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.[6]

Ecology

Cyclotosaurus are thought to have been semi-aquatic carnivores, though feeding strategies likely differed between species.[7]

References

  1. ↑ Hans-Dieter Sues, Nicholas C. Frase (2010). Triassic Life on Land: The Great Transition. Columbia University Press. p. 87. ISBN 023113522X.
  2. ↑ Temnospondyli
  3. ↑ Schoch, Rainer (2008). "The Capitosauria (Amphibia): characters, phylogeny, and stratigraphy". Palaeodiversity 1: 189–226.
  4. ↑ 4.0 4.1 4.2 Damiani, Ross J. (2001). "A systematic revision and phylogenetic analysis of Triassic mastodonsauroids (Temnospondyli: Stereospondyli)". Zoological Journal of the Linnean Society 133 (4): 379–482. doi:10.1111/j.1096-3642.2001.tb00635.x.
  5. ↑ Jenkins, F. A. Jr.; Shubin, N. H.; Amaral, W. W.; Gatesy, S. M.; Schaff, C. R.; Clemmensen, L. B.; Downs, W. R.; Davidson, A. R.; Bonde, N.; Osbaeck, F. (1994). "Late Triassic continental vertebrates and depositional environments of the Fleming Fjord Formation, Jameson Land, East Greenland". Meddelelser om Grønland, Geoscience 32: 1–25.
  6. ↑ 6.0 6.1 Ingavat, Rucha; Janvier, Phillippe (1981). "Cyclotosaurus cf. Posthumus Fraas (Capitosauridae, Stereospondyli) from the Huai Hin Lat Formation (Upper Triassic), Northeastern Thailand". Geobios 14 (6): 711–25. doi:10.1016/S0016-6995(81)80149-0.
  7. ↑ 7.0 7.1 7.2 Sulej, T.; Majer, D. (2005). "The temnospondyl amphibian Cyclotosaurus from the Upper Triassic of Poland". Palaeontology 48: 157–70. doi:10.1111/j.1475-4983.2004.00430.x.
  8. ↑ Fraser, Nicholas C; Sues, Hans-Dieter (1997). In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods. Cambridge University Press. p. 143.
  9. ↑ 9.0 9.1 Nicholas C. Fraser, Hans-Dieter Sues (1997). In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods. Cambridge University Press. p. 8. ISBN 0521458994.