Opallionectes
Encyclopedia
Opallionectes andamookaensis (meaning "the opal swimmer from Andamooka") is the name given to a 5 m (16 ft) long plesiosaur
, which is thought to have lived during the early Cretaceous
period (Lower middle Aptian
), 115 million years ago, in shallow seas covering what is now Australia
.
An opalized partial skeleton (including vertebrae, ribs, limb elements, teeth, and associated gastroliths) of the animal has been discovered in an opal
mine at Andamooka in South Australia and described by Kear in 2006. It had fine needle like sharp teeth similar to those of nothosaur
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, 65 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.
Plesiosaur
Plesiosauroidea is an extinct clade of carnivorous plesiosaur marine reptiles. Plesiosauroids, are known from the Jurassic and Cretaceous Periods...
, which is thought to have lived during the early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
period (Lower middle Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
), 115 million years ago, in shallow seas covering what is now Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
.
An opalized partial skeleton (including vertebrae, ribs, limb elements, teeth, and associated gastroliths) of the animal has been discovered in an opal
Opal
Opal is an amorphous form of silica related to quartz, a mineraloid form, not a mineral. 3% to 21% of the total weight is water, but the content is usually between 6% to 10%. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most...
mine at Andamooka in South Australia and described by Kear in 2006. It had fine needle like sharp teeth similar to those of nothosaur
Nothosaur
Nothosaurs were Triassic marine sauropterygian reptiles that may have lived like seals of today, catching food in water but coming ashore on rocks and beaches. 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...
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, 65 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.