Aristonectes

Aristonectes (meaning 'best swimmer') is an extinct genus of plesiosaur from the Late Cretaceous Paso del Sapo Formation of what is now Argentina, the Quiriquina Formation of Chile and the Lopez de Bertodano Formation of Antarctica. The type species is Aristonectes parvidens, first named by Cabrera in 1941.

Aristonectes
Temporal range: Maastrichtian
~
Reconstruction of Aristonectes parvidens with Diplomoceras
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: †Sauropterygia
Order: †Plesiosauria
Family: †Elasmosauridae
Subfamily: †Aristonectinae
Genus: †Aristonectes
Cabrera 1941
Species
  • A. parvidens Cabrera 1941 (type)
  • A. quiriquinensis Otero et al. 2014

Description
Scale compared to human of Aristonectes quiriquinensis

Aristonectes quiriquinensis was a large plesiosaur, with the holotype measuring over 10 metres (33 ft) long and weighing 4 metric tons (4.4 short tons).[1][2] A rough estimate based on the specimen from the Lopez de Bertodano Formation (identified as cf. Aristonectes sp.) indicates that Aristonectes was one of the largest plesiosaurs ever to exist, with an estimated body length of 11–11.9 metres (36–39 ft) and an estimated body mass of 10.7–13.5 metric tons (11.8–14.9 short tons).[3][lower-alpha 1]

Classification
Life reconstruction of Aristonectes quiriquinensis

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. 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.[4] Subsequent study, however, revalidated Morturneria based on non-ontogenetic differences from Aristonectes.[5]

Aristonectes was placed within its own family, Aristonectidae, along with Tatenectes, Kaiwhekea, and Kimmerosaurus, by O'Keefe and Street (2009), as sister family of the polycotylid cryptoclidoids. However, subsequent studies (Otero et al., 2014)[6][7] returned Aristonectes to Elasmosauridae, recovering the genus as a derived elasmosaurid and therefore relegating Aristonectidae to a subfamily of Elasmosauridae, as Aristonectinae.

See also

Notes
  1. The body mass estimate per O'Gorman and his colleagues is based on their assumption that Cryptoclidus and Aristonectes had similar body proportions.[3]

References
  1. Rodrigo A. Otero; Sergio Soto-Acuña; Frank R. O'keefe (2018). "Osteology of Aristonectes quiriquinensis (Elasmosauridae, Aristonectinae)". Journal of Vertebrate Paleontology. 38 (1). e1408638. doi:10.1080/02724634.2017.1408638. S2CID 90977078.
  2. Paul, Gregory S. (2022). The Princeton Field Guide to Mesozoic Sea Reptiles. Princeton University Press. p. 119. ISBN 9780691193809.
  3. O'Gorman, J.P.; Santillana, S.; Otero, R.; Reguero, M. (2019-10-01). "A giant elasmosaurid (Sauropterygia; Plesiosauria) from Antarctica: New information on elasmosaurid body size diversity and aristonectine evolutionary scenarios". Cretaceous Research. 102: 37–58. doi:10.1016/j.cretres.2019.05.004. ISSN 0195-6671. S2CID 181725020.
  4. Gasparini, Z., Bardet, N., Martin, J.E. and Fernandez, M.S. (2003) "The elasmosaurid plesiosaur Aristonectes Cabreta from the Latest Cretaceous of South America and Antarctica". Journal of Vertebrate Paleontology 23(1): 104-115.
  5. O'Keefe, F., Otero, R., Soto-Acuña, S., O'gorman, J., Godfrey, S., Chatterjee, S. 2017. Cranial anatomy of Morturneria seymourensis from Antarctica, and the evolution of filter feeding in plesiosaurs of the Austral Late Cretaceous. Journal of Vertebrate Paleontology. doi: 10.1080/02724634.2017.1347570
  6. Otero, R. A., Soto-Acuña, S. and Rubilar-Rogers, D. 2012. A postcranial skeleton of an elasmosaurid plesiosaur from the Maastrichtian of central Chile, with comments on the affinities of Late Cretaceous plesiosauroids from the Weddellian Biogeographic Province. Cretaceous Research, 37: 89–99.
  7. Otero et al. (2014), Aristonectes quiriquinensis, sp. nov., a new highly derived elasmosaurid from the upper Maastrichtian of central Chile
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