''Subcyclotosaurus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

prehistoric mastodonsaurid

temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order (biology), order of small to giant tetrapods—often considered Labyrinthodontia, primitive amphi ...

amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...

. It is known from a single partial skull from the

Hawkesbury Sandstone Sydney sandstone is the common name for Sydney Basin Hawkesbury Sandstone, one variety of which is historically known as Yellowblock, and also as "yellow gold" a sedimentary rock named after the Hawkesbury River north of Sydney, where this ...

formation in Australia.

Discovery and naming

The remains of the type specimen ''Subcyclotosaurus brookvalensis'' were discovered in the

formation, Australia, which is in an

Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Triassic Ep ...

lacustrine shale deposit. The genus and specific name was assigned by Watson in 1958.

Description

The type specimen (AM F47499) is a partial skull roof, with fragments lost on the right side. The dorsal surface of the skull resembles a small Cyclotosaur skull from the Brookvale clays of the

Material was copied from this source, which is available under a Creative Commons License. The specimen is from the mould of a skull broken so that the right border is lost, and is very slightly distorted by pressure so that the orbits are no longer symmetrical. The proportions of the skull resemble those of most others of ''

Cyclotosaurus ''Cyclotosaurus'' is an extinct genus of temnospondyl within the family Mastodonsauridae. It was of great size for an amphibian, had an elongated skull up to . Etymology The name means "round eared lizard" in Ancient Greek, derived from round ...

'', the preorbital length being 66% of the total mid-line length. The extremes amongst ''

'' being 61% in the small ''

ebrachensis'', and 71% in ''

Parotosuchus ''Parotosuchus'' is an extinct genus of capitosaurian temnospondyl amphibians within the family Mastodonsauridae. Fossils are known from the Early Triassic of Europe, Africa, Australia, and Antarctica. It was about long and likely lived in aqua ...

helgolandicus''. The skull is characterized by the small tabular without any trace of a "horn", but with a round lappet that approaches the squamosal flange lateral to the tympanic membrane, failing to meet it by about its own width. The occiput between the otic notches is proportionately wide, a reflection of the small size of the skull. The skull is otherwise of normal ''Parotosuchus'' structure, but has a small internasal vacuity between the dorsal processes of the premaxillae. Lateral lines are often shown as continuous grooves with well-defined borders. A deep groove on the maxilla begins immediately behind and lateral to the nostril and passes straight back to the lachrymal, on which bone it turns outward and forward and ends abruptly. Another groove appears to begin on the maxilla, immediately lateral to that described above. It passes back just above the insertion of the teeth for the full length of the bone. The supraorbital groove begins abruptly on the dorsal surface of the premaxilla, immediately passes on to the nasal, and extends back on that bone close to its suture with the lachrymal. It then comes on to the prefrontal, passing on to the frontal where that bone enters the orbital border. Then as a well-defined groove it surrounds the hinder part of the orbit, turns vertically on to the jugal, and then backward to cross the point where jugal, quadratojugal and squamosal meet, continuing over the squamosal to pass back on to the body. There is a canal crossing the supratemporal.

Discovery and naming

Description

References

See also