''Opallionectes andamookaensis'' (meaning "the opal swimmer from Andamooka") is the name given to a 5 m (16 ft) long

cryptoclidia Plesiosauroidea (; Ancient Greek, Greek: 'near, close to' and 'lizard') is an extinct clade of carnivore, carnivorous Marine (ocean), marine Reptilia, reptiles. They have the snake-like longest neck to body ratio of any reptile. Plesiosauroid ...

plesiosaur The Plesiosauria or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...

, which is thought to have lived during the early

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

period (Lower middle

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

), 115 million years ago, in shallow seas covering what is now

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

Description

An opalized partial skeleton (including vertebrae, ribs, limb elements, teeth, and associated

gastroliths A gastrolith, also called a stomach stone or gizzard stone, is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. In oth ...

) of the animal has been discovered in an

opal Opal is a hydrated amorphous form of silicon dioxide, silica (SiO2·''n''H2O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to the amorphous (chemical) physical structure, it is classified as a ...

mine in the Bulldog Shale at Andamooka in

South Australia South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...

and described by Kear in 2006.Kear, 2006 It had fine needle like sharp teeth similar to those of

nothosaur Nothosaurs (superfamily Nothosauroidea) were Triassic marine sauropterygian reptiles. They averaged about in length, with a long body and tail. The feet were paddle-like, and are known to have been webbed in life, to help power the animal when sw ...

s and were probably used to trap small prey such as fish and squids. It is considered a sort of missing link between the much older plesiosaurs, living 165 million years ago, and the ones near the end of the Cretaceous, 66 million years ago, between which there had been a gap in the fossil record. Analyses of the sedimentary structures, fossils, isotope data and climatic modeling show that ''Opallionectes'' lived in a region characterized by seasonally cold (possibly freezing) conditions, suggesting that it had developed some adaptation to live in cold water, such as seasonal migration or elevated metabolism.

References

Bibliography

* Cryptoclididae Early Cretaceous plesiosaurs Enigmatic plesiosaur taxa Early Cretaceous reptiles of Australia Plesiosaurs of Oceania Aptian life Opals Fossils of Australia Fossil taxa described in 2006 Sauropterygian genera {{plesiosaur-stub

Description

See also

References

Bibliography