''Aristonectes'' (meaning 'best swimmer') is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of plesiosaur from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

Paso del Sapo Formation The Paso del Sapo Formation is a Maastrichtian geologic formation of the Cañadón Asfalto Basin in Argentina. The siltstones of the formation were deposited in a lacustrine environment. Plesiosaur remains are among the fossils that have been re ...

of what is now

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, t ...

, the Quiriquina Formation of

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...

and the Lopez de Bertodano Formation of

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest co ...

. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

is ''Aristonectes parvidens'', first named by Cabrera in 1941.

Description

Analysis of a specimen from the Lopez de Bertodano Formation indicates that ''Aristonectes'' was one of the largest plesiosaurs ever to exist, with an estimated body length of and body mass of per Paul and per O'Gorman and his colleagues.

Classification

''Aristonectes'' was classified variously since its original 1941 description, but a 2003 review of plesiosaurs from Patagonia conducted by Gasparini ''et al.'' (2003) found that ''Aristonectes'' was most closely related to elasmosaurid plesiosaurs like ''

Elasmosaurus ''Elasmosaurus'' (;) is a genus of plesiosaur that lived in North America during the Campanian stage of the Late Cretaceous period, about 80.5million years ago. The first specimen was discovered in 1867 near Fort Wallace, Kansas, US, and was se ...

''. The authors also considered '' Morturneria'' a junior synonym of ''Aristonectes'' because the former's holotype has unfused neural arches of the vertebrae indicative of juvenile status. Subsequent study, however, revalidated ''Morturneria'' based on non-ontogenetic differences from ''Aristonectes''. ''Aristonectes'' was placed within its own family, Aristonectidae, along with '' Tatenectes'', '' Kaiwhekea'', and ''

Kimmerosaurus ''Kimmerosaurus'' ("lizard from Kimmeridge") is an extinct genus of plesiosaur from the family Cryptoclididae. ''Kimmerosaurus'' is most closely related to ''Tatenectes''. Discovery There are very few fossil remains of ''Kimmerosaurus'' known. ...

'', by O'Keefe and Street (2009), as sister family of the polycotylid cryptoclidoids. However, subsequent studies (Otero ''et al.'', 2014)Otero ''et al.'' (2014), ''Aristonectes quiriquinensis'', sp. nov., a new highly derived elasmosaurid from the upper Maastrichtian of central Chile
/ref> returned ''Aristonectes'' to Elasmosauridae, recovering the genus as a derived elasmosaurid and therefore relegating Aristonectidae to a subfamily of Elasmosauridae, as Aristonectinae.

Notes

References

External links

Taxonomic history of ''Aristonectes''
{{Taxonbar, from=Q2154474 Late Cretaceous plesiosaurs Maastrichtian life Late Cretaceous reptiles of South America Plesiosaurs of South America Cretaceous Argentina Fossils of Argentina Cañadón Asfalto Basin Cretaceous Chile Fossils of Chile Cretaceous Antarctica Fossils of Antarctica Fossil taxa described in 1941 Sauropterygian genera

Description

Classification

See also

Notes

References

External links