aristonectinae

{{Short description|Extinct clade of reptiles}}

{{merge|Aristonectidae|target=Elasmosauridae|discuss=Talk:Aristonectidae#Redirect?|date=January 2025}}

{{Automatic taxobox

| fossil_range = Campanian-Maastrichtian
~{{fossil range|72|66}}

| image = Aristonectes_parvidens.png

| image_upright = 1.15

| image_caption = Life restoration of Aristonectes parvidens

| taxon = Aristonectinae

| authority = Otero et al., 2012

| subdivision_ranks = Genera

| subdivision =

• {{extinct}}Alexandronectes
• {{extinct}}Aristonectes
• {{extinct}}Kaiwhekea
• {{extinct}}Morturneria
• {{extinct}}Wunyelfia

}}

Aristonectinae is a subfamily of plesiosaurs in the family Elasmosauridae. It includes the Late Cretaceous plesiosaurs Aristonectes and Kaiwhekea, traditionally grouped with the Late Jurassic Tatenectes and Kimmerosaurus in the family Aristonectidae. They are distinguished by the fact that they have a very enlarged skull compared to the width of the body, a moderately short neck and more than 25 teeth in the maxilla.{{cite journal|author1=Rodrigo A. Otero|author2=Sergio Soto-Acuña|author3=David Rubilar-Rogers|title=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|journal=Cretaceous Research|year=2012|volume=37|pages=89–99|doi=10.1016/j.cretres.2012.03.010|s2cid=129841690|bibcode=2012CrRes..37...89O|url=https://www.researchgate.net/publication/233402744}}

An alternative hypothesis suggested by F. Robin O'Keefe and Hallie Street in 2009 is that aristonectines instead belong to a family—Aristonectidae—which is unrelated to elasmosaurids and is instead the sister group to Polycotylidae within the larger clade "Cryptocleidoidea".{{cite journal |doi=10.1671/039.029.0118 |title=Osteology of the cryptocleidoid plesiosaur Tatenectes laramiensis , with comments on the taxonomic status of the Cimoliasauridae |date=2009 |last1=O'Keefe |first1=F. Robin |last2=Street |first2=Hallie P. |journal=Journal of Vertebrate Paleontology |volume=29 |issue=1 |pages=48–57 |bibcode=2009JVPal..29...48O }}