Cyclotosaurus

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. 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 in the Late Triassic, and represents the last of the mastodonsaurids.

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 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. Cyclotosaurus hemprichi is known from the Norian (Late Triassic) age Knollenmergel of Halberstadt, and Cyclotosaurus posthumus from the Stubensandstein (Norian) in Pfaffenhofen. 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. 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 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

References

1. Schoch, Rainer. (2008). "The Capitosauria (Amphibia): characters, phylogeny, and stratigraphy". Palaeodiversity.
2. Jenkins, F. A. Jr.. (1994). "Late Triassic continental vertebrates and depositional environments of the Fleming Fjord Formation, Jameson Land, East Greenland". Meddelelser om Grønland, Geoscience.
3. (1981). "''Cyclotosaurus'' cf. ''Posthumus'' Fraas (Capitosauridae, Stereospondyli) from the Huai Hin Lat Formation (Upper Triassic), Northeastern Thailand". Geobios.
4. PATON, R. L. 1974. Capitosauroid labyrinthodonts from the Trias of England. Palaeontology, 17, 253–289, pls 35–36.
5. Damiani, Ross J.. (2001). "A systematic revision and phylogenetic analysis of Triassic mastodonsauroids (Temnospondyli: Stereospondyli)". Zoological Journal of the Linnean Society.
6. (2005). "The temnospondyl amphibian ''Cyclotosaurus'' from the Upper Triassic of Poland". Palaeontology.
7. (2016). "A new species of Cyclotosaurus (Stereospondyli, Capitosauria) from the Late Triassic of Bielefeld, NW Germany, and the intrarelationships of the genus". Fossil Record.
8. 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
9. (June 2019). "A large temnospondyl humerus from the Rhaetian (Late Triassic) of Bonenburg (Westphalia, Germany) and its implications for temnospondyl extinction". Journal of Iberian Geology.