Eocyclotosaurus
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| Eocyclotosaurus Temporal range: Middle Triassic | |
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Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Tetrapoda |
| Order: | †Temnospondyli |
| Suborder: | †Stereospondyli |
| Clade: | †Capitosauria |
| Family: | †Heylerosauridae |
| Genus: | †Eocyclotosaurus Ortlam, 1970 |
| Type species | |
| †E. woschmidti Ortlam, 1970 | |
| Other species | |
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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.
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]
The genus Eocyclotosaurus was named by Dieter Ortlam in 1970.[4] The type species is Eocyclotosaurus woschmidti, the specific name honouring Wolfgang Schmidt.
Description
Compered 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
The 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
The tabular horn is situated on the side and toward the back of the body / laterally directed and suturing with the squamosal posteriorly.[8] The parasphenoid 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
The phylogenetic position of the genus Eocyclotosaurus within the capitosaur taxa according to Witzmann et al. (2016)[9]
