Eocyclotosaurus (Greek ‘èoos’ = dawn, ‘kyklos’ = circle, 'ous' = ear ) is an extinct genus of mastodonsauroid temnospondyl from the Middle Triassic (Anisian). The name Eocyclotosaurus means "dawn round-eared lizard".[1] It is characterized as a capitosauroid with a long and slender snout, closed otic fenestra, and small orbits.[2] It measured over one metre and had a 22 cm skull.
| Eocyclotosaurus Temporal range: Middle Triassic
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Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Order: | †Temnospondyli |
| Suborder: | †Stereospondyli |
| Clade: | †Capitosauria |
| Family: | †Heylerosauridae |
| Genus: | †Eocyclotosaurus Ortlam, 1970 |
| Type species | |
| †E. woschmidti Ortlam, 1970
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| Other species | |
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It lived between 247 and 242 million years ago in both North America, Germany, France and the British Isles during the early Triassic.[3][4]
Discovery and naming
editThe genus Eocyclotosaurus was named by Dieter Ortlam in 1970.[4] The type species is Eocyclotosaurus woschmidti, the specific name honouring Wolfgang Schmidt.
Description
editCompered to Cyclotosaurus, Eocyclotosaurus has a similar morphology in postorbital division of the skull. However, in Eocyclotosaurus the depth of the occiput is greater.[4]
Skull
editThe species is narrow-headed.[5] Orbits were smaller in Eocyclotosaurus and related forms compared to other taxa such as Mastodonsaurus who had up to three times the size of smaller eyed taxa.[6] Posteromedial expansion is absent in Eocyclotosaurus, due to anterior snout region being narrower.[1] Premaxillary teeth are transversely elongated. The jaw is heavily reticulated and has a ridge and groove ornamentation of the angular.[7]
Unambiguous autapomorhies
editThe tabular horn is situated on the side and toward the back of the body / laterally directed and suturing with the squamosal posteriorly.[8] The paraspenoid cultriform process is expanded at the base and constricted at midlength.[8] The upper jaw condyle does not join with the quadratojugal. The vomerine plate lies anterior to the interpterygoid vacuities and is elongate.[8] The parasphenoid cultriform process is deep and thin ventrally.[8] The parasphenoid cultriform process is underplated by posterior extension of the vomer.[8]
Phylogeny
editThe phylogenetic position of the genus Eocyclotosaurus within the capitosaur taxa according to Witzmann et al. (2016)[9]
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Paleobiology
editThe skull of Eocyclotosaurus was more suited for capturing small prey compared to Cyclotosaurus who was tested to have more capabilities to hunt larger prey.[10] Feeding mechanism and diet: It has been analyzed to capture small prey using a side striking behavior.[10][11] General scenarios for eating heavier for temnospondyls are inferred based on their atomical evidence. Prey would be captured in their teeth, manipulated into swallowing position by their tongue, and swallowed with the assistance of their tongue.[10] The reduction of the cross section of its skull and the elongation of its nasal bones was an adaptation to reduce drag during lateral movement of the head, increasing the efficiency of aquatic feeding.[8]
Paleoecology
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Its habitat was aquatic. Discovered in the 1980s, Northeastern New Mexico has the most abundant bonebed of Eocyclotosaurus.[9]
Stratigraphic and geographic range
editBy the early Anison, most major crown clades were present: heylerosaurids (Eocyclotosaurus), mastodonsaurids, stenotosaurids.[1] The origin of the genus Eocyclotosaurus was at the Spanthaian and Anisian boundary, separate from Cyclotosaurus in the late Ladiunian.[11] Separate evolution suggest separate stratigraphy.[11]
Images
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References
edit- ^ a b c Schoch, Rainer R. (2019-05-24). "Osteology of the temnospondyl Trematosaurus brauni Burmeister, 1849 from the Middle Buntsandstein of Bernburg, Germany". Palaeodiversity. 12 (1): 41. doi:10.18476/pale.v12.a4. ISSN 1867-6294.
- ^ LUCAS, SPENCER G.; SCHOCH, RAINER R. (2007-01-02). "Triassic temnospondyl biostratigraphy, biochronology and correlation of the German Buntsandstein and North American Moenkopi Formation". Lethaia. 35 (2): 97–106. doi:10.1111/j.1502-3931.2002.tb00071.x. ISSN 0024-1164.
- ^ Rinehart, L. F. "Eocyclotosaurus appetolatus, a middle triassic amphibian: Osteology, life history, and paleobiology". New Mexico Museum of Natural History & Science Bulletin. 70: 1–118.
- ^ a b c "PBDB". paleobiodb.org. Retrieved 2023-03-06.
- ^ Schoch, Rainer R. (2011-07-01). "How diverse is the temnospondyl fauna in the Lower Triassic of southern Germany?". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 261 (1): 49–60. doi:10.1127/0077-7749/2011/0147. ISSN 0077-7749.
- ^ Marcé-Nogué, Jordi; Fortuny, Josep; De Esteban-Trivigno, Soledad; Sánchez, Montserrat; Gil, Lluís; Galobart, Àngel (2015-06-24). "3D Computational Mechanics Elucidate the Evolutionary Implications of Orbit Position and Size Diversity of Early Amphibians". PLOS ONE. 10 (6): e0131320. Bibcode:2015PLoSO..1031320M. doi:10.1371/journal.pone.0131320. ISSN 1932-6203. PMC 4479603. PMID 26107295.
- ^ Rinehart, L. F.; Lucas, S. G. (2012-04-27). "Function of dermal bone texture in Middle Triassic Temnospondyl amphibians from New Mexico". Proceedings Volume: "Evaluating How Continental Sedimentary Basins Fill: Development and Preservation of Sedimentary Successions", New Mexico Geological Society, 2012 Annual Spring Meeting. Socorro, NM: New Mexico Geological Society. doi:10.56577/sm-2012.197.
- ^ a b c d e f Steyer, J. Sébastien; Boulay, Marc; Lorrain, Sylvia (September 2010). "3D external restorations of stegocephalian skulls using ZBrush: The renaissance of fossil amphibians". Comptes Rendus Palevol. 9 (6–7): 463–470. doi:10.1016/j.crpv.2010.07.007. ISSN 1631-0683.
- ^ a b Witzmann, Florian; Sachs, Sven; Nyhuis, Christian J. (2016-03-23). "A new species of Cyclotosaurus (Stereospondyli, Capitosauria) from the Late Triassic of Bielefeld, NW Germany, and the intrarelationships of the genus". Fossil Record. 19 (2): 83–100. doi:10.5194/fr-19-83-2016. ISSN 2193-0074.
- ^ a b c Fortuny, Josep; Marcé-Nogué, Jordi; Gil, Lluis; Galobart, Àngel (2012-05-09). "Skull Mechanics and the Evolutionary Patterns of the Otic Notch Closure in Capitosaurs (Amphibia: Temnospondyli)". The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology. 295 (7): 1134–1146. doi:10.1002/ar.22486. ISSN 1932-8486. PMID 22573567.
- ^ a b c Schoch, Rainer R. (October 2000). "The Origin And Intrarelationships Of Triassic Capitosaurid Amphibians". Palaeontology. 43 (4): 705–727. doi:10.1111/1475-4983.00146.