''Clevosaurus'' (meaning "Gloucester lizard") is an extinct genus of
rhynchocephalia
Rhynchocephalia (; ) is an order of lizard-like reptiles that includes only one living species, the tuatara (''Sphenodon punctatus'') of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a diverse g ...
n reptile from the
Late Triassic
The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...
and the
Early Jurassic
The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
periods. Species of ''Clevosaurus'' were widespread across
Pangaea
Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million y ...
, and have been found on all continents except Australia and Antarctica.
Five species of ''Clevosaurus'' have been found in ancient fissure fill deposits in south-west England and Wales, alongside other sphenodontians, early mammals and dinosaurs. In regards to its Pangaean distribution, ''C. hadroprodon'' is the oldest record of a sphenodontian from Gondwana,
though its affinity to ''Clevosaurus'' has been questioned.
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
Gloucestershire ( abbreviated Glos) is a county in South West England. The county comprises part of the Cotswold Hills, part of the flat fertile valley of the River Severn and the entire Forest of Dean.
The county town is the city of Gl ...
, England, with the name of the county lending its name to the genus.
Description
![Clevosaurus brasiliensis](https://upload.wikimedia.org/wikipedia/commons/6/69/Clevosaurus_brasiliensis.jpg)
''Clevosaurus'' was a medium-sized sphenodontian that was estimated to reach full length of ~25 cm (''Clevosaurus hudsoni''). The skull length could range from as little as 14 mm in ''C. sectumsemper'' and up to 40 mm in ''C. hudsoni''. Notable for their greatly reduced number of teeth (3-6 per jaw quadrant), broad skulls and shortened snouts. The teeth of european clevosaurs 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
![Clevosaurus restoration](https://upload.wikimedia.org/wikipedia/commons/9/91/Clevosaurus_restoration.jpg)
Species of ''Clevosaurus'' were likely insectivorous. Biomechanical modelling suggests that they had high enough tooth pressures and strong enough bite force to crush
chitin
Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...
, indicating that they had the ability to feed on thick-shelled beetles as well as possibly small vertebrates.
List of species
* †''Clevosaurus bairdi'' Sues et al. 1994
McCoy Brook Formation
The McCoy Brook Formation is a geological formation dating to roughly between 200 and 190 million years ago and covering the Hettangian to Sinemurian stages. The McCoy Brook Formation is found in outcrops around the Bay of Fundy, Nova Scotia.
...
, Canada,
Hettangian
* †''Clevosaurus brasiliensis'' Bonaparte and Sues 2006
Caturrita Formation
The Caturrita Formation is a rock formation found in Rio Grande do Sul, Brazil. Its sediments were deposited in the Paraná Basin. The formation is from the Upper Triassic and forms part of the Santa Maria Supersequence in the upper section of th ...
, Brazil,
Norian
The Norian is a division of the Triassic Period. It has the rank of an age (geochronology) or stage (chronostratigraphy). It lasted from ~227 to million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.
Stratigraphic defi ...
* †''Clevosaurus cambrica'' Keeble et al. 2018
Pant-y-ffynnon Quarry
Pant-y-Ffynnon Quarry is a stone quarry in the Vale of Glamorgan, Wales, around 3 kilometers east of Cowbridge. It contains fissure fill deposits dating to the Late Triassic ( Rhaetian), hosted within karsts of Carboniferous aged limestone, pri ...
fissure fill, Wales,
Rhaetian
The Rhaetian is the latest age of the Triassic Period (in geochronology) or the uppermost stage of the Triassic System (in chronostratigraphy). It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest age ...
* †''Clevosaurus convallis'' Saila 2005 St. Bride's Island fissure fill, Wales, Hettangian
* †''Clevosaurus hadroprodon'' Hsiou et al. 2019
Santa Maria Formation
The Santa Maria Formation is a sedimentary rock formation found in Rio Grande do Sul, Brazil. It is primarily Carnian in age (Late Triassic), and is notable for its fossils of cynodonts, "rauisuchian" pseudosuchians, and early dinosaurs and oth ...
, Brazil,
Carnian
The Carnian (less commonly, Karnian) is the lowermost stage of the Upper Triassic Series (or earliest age of the Late Triassic Epoch). It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followed by t ...
* †''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 Woodleaze Quarry fissure fill, England, Rhaetian
The three species known from the
Sinemurian
In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is ...
aged
Lufeng Formation
The Lufeng Formation (formerly Lower Lufeng Series) is a Lower Jurassic sedimentary rock formation found in Yunnan, China. It has two units: the lower Dull Purplish Beds/Shawan Member are of Hettangian age, and Dark Red Beds/Zhangjia'ao Member ar ...
of China (''C. mcgilli, C.wangi'' and ''C. petilus'') are now considered indeterminate within the genus. Indeterminate remains are also known from the
Stormberg Group (either
Elliot
Elliot (also spelled Eliot, Elliotte, Elliott, Eliott and Elyot) is a personal name which can serve as either a surname or a given name. Although the given name has historically been given to males, females have increasingly been given the name ...
or
Clarens Formation
The Clarens Formation is a geological formation found in several localities in Lesotho and in the Free State, KwaZulu-Natal, and Eastern Cape provinces in South Africa. It is the uppermost of the three formations found in the Stormberg Group of ...
) of South Africa, dating to the Hettangian.
Phylogeny
Below is a
cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...
of the relationships within Clevosauridae based on the
phylogenetic analysis
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
of Hsiou et al. (2015):
''"Clevosaurus" latidens'' was recovered outside of Clevosauridae, as the
sister taxon
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and t ...
of
Opisthodontia.
[ It was subsequently assigned to a new genus, '' Fraserosphenodon'', in 2018.]
References
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.
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Taxa named by William Elgin Swinton
Prehistoric reptile genera
Paleontology in Nova Scotia