Clevosaurus (meaning "Gloucester lizard") is an extinct genus of reptile from the Triassic and the Jurassic periods. Species of Clevosaurus were widespread across Pangaea, and have been found on all continents except Australia and Antarctica.
History of discovery
The first species of
Clevosaurus to be described was
C. hudsoni, which was described by William Elgin Swinton in 1939 from a fissure fill deposit in Cromhall Quarry (Magnesian Conglomerate Formation) in the county of
Gloucestershire, England, with the name of the county lending its name to the genus.
[W. E. Swinton. (1939). A new Triassic rhynchocephalian from Gloucestershire. Annals and Magazine of Natural History: Zoology, Botany, and Geology 4:591-594]
Another notable specimen was discovered in 1953 in Cromhall Quarry alongside the holotype of Cryptovaranoides.
Description
Species of
Clevosaurus varied in body size, with
Clevosaurus sectumsemper having an estimated total length of , while
C. hudsoni had a total length of around
. The skull length could range from as little as in
C. sectumsemper and up to in
C. hudsoni.
The reptilian encephalisation quotient (REQ) of
C. brasiliensis is much lower than that of the modern tuatara, whose REQ is 0.84–1.16.
The teeth of European
Clevosaurus tended to be mesio-distally elongated, blade-like, and occluded precisely with the opposite pair of teeth, leaving conspicuous diagonal wear facets and acting as a self-sharpening cutting surface.
However, the teeth of
C. brasiliensis have a very different morphology with no diagonal wear facets, the teeth of the dentary are all conical excluding the posterior-most tooth which can be up to three-times bigger than any of the other teeth, they also have a unique form of implantation, where the base of the teeth sit deeply within the jaw bones, which is not known of in any other rhynchocephalian.
Paleobiology
of
Clevosaurus were likely insectivorous. Biomechanical modelling suggests that they had high enough tooth pressures and strong enough bite force to crush
chitin, indicating that they had the ability to feed on thick-shelled beetles as well as possibly small vertebrates.
Taxonomy
At least 9 species of
Clevosaurus are considered valid:
-
† Clevosaurus bairdi Sues et al. 1994 McCoy Brook Formation, Canada, Early Jurassic (Hettangian)
-
† Clevosaurus brasiliensis Bonaparte and Sues 2006
-
† Clevosaurus cambrica Keeble et al. 2018
-
† Clevosaurus convallis Saila 2005
-
† Clevosaurus hadroprodon Hsiou et al. 2019
-
† Clevosaurus hudsoni Swinton 1939 Cromhall Quarry fissure fill, England, Rhaetian
-
† Clevosaurus minor Fraser 1988 Cromhall Quarry fissure fill, England, Rhaetian
-
† Clevosaurus sectumsemper Klein et al. 2015
-
† Clevosaurus nicholasi Bhat et al. 2023
The three species known from the
Sinemurian aged
Lufeng Formation of China (
C. mcgilli, C.wangi and
C. petilus) are now considered indeterminate within the genus.
[Jones MEH. 2006 The Early Jurassic clevosaurs from China (Diapsida: Lepidosauria). New Mex. Museum Nat. Hist. Sci. Bull. 37, 548–562.] Indeterminate remains are also known from the
Stormberg Group (either
Elliot Formation or Clarens Formation) of South Africa, dating to the Hettangian.
Indeterminate clevosaur remains, possibly representing
Clevosaurus, are also known from the Norian aged Fleming Fjord Group of
Jameson Land, east Greenland.
Below is a cladogram of the relationships within Clevosauridae based on the phylogenetic analysis of Hsiou et al. (2015):
"Clevosaurus" latidens was recovered outside of Clevosauridae, as the sister taxon of Opisthodontia.[ It was subsequently assigned to a new genus, Fraserosphenodon, in 2018.]
Clevosaurus is considered to be a member of the group Eusphenodontia by the groups definition, due to it possessing characters not shared with more primitive sphenodontians. By definition, it is excluded from Neosphenodontia.
Position of Clevosaurus within Rhynchocephalia, after DeMar et al. 2022.
Additional reading
-
Paleofile
-
Gill PG, Säilä LK, Corfe IJ, Challands TJ, Williams M, Clemens WA (2006). The fauna and palaeoenvironment of St. Brides Island: Evidence from the lower Jurassic fissure fills of South Wales. In Barrett PM, Evans SE (eds.). Ninth international symposium on Mesozoic terrestrial ecosystems and biota. pp 48−51. London: Natural History Museum.
-
Jones MEH (2006) The Early Jurassic clevosaurs from China (Diapsida: Lepidosauria). Natl Mus Nat Hist Sci Bull, 37:548–562.
-
Jones MEH (2009). Dentary tooth shape in Sphenodon and its fossil relatives (Diapsida: Lepidosauria: Rhynchocephalia). In Koppe T, Meyer G, Alt KW, (eds). Interdisciplinary Dental Morphology, Frontiers of Oral Biology (vol 13). Greifswald, Germany; Karger. 9–15.
