Opinions from S. P. Welles 1943
- 'Alzadasaurus belongs to Elasmosauridae'
- 'Alzadasaurus riggsi belongs to Alzadasaurus'
- 'Aphrosaurus belongs to Elasmosauridae'
- 'Aphrosaurus furlongi belongs to Aphrosaurus'
- 'Brimosaurus is a nomen dubium'
- 'Brimosaurus grandis is a nomen dubium'
- 'Cimoliasaurus is a nomen dubium'
- 'Cimoliasaurus magnus is a nomen dubium'
- 'Discosaurus carinatus is an objective synonym of Elasmosaurus platyurus'
- 'Elasmosauridae belongs to Plesiosauroidea'
- 'Elasmosaurus belongs to Elasmosauridae'
- 'Elasmosaurus marshii is recombined as Thalassonomosaurus marshii'
- 'Elasmosaurus nobilis is recombined as Thalassonomosaurus nobilis' according to Williston 1906
- 'Elasmosaurus nobilis is recombined as Thalassonomosaurus nobilis'
- 'Elasmosaurus platyurus belongs to Elasmosaurus'
- 'Elasmosaurus serpentinus is recombined as Hydralmosaurus serpentinus'
- 'Elasmosaurus sternbergi is a nomen dubium'
- 'Fresnosaurus belongs to Elasmosauridae'
- 'Hydralmosaurus belongs to Elasmosauridae'
- 'Hydrotherosaurus belongs to Elasmosauridae'
- 'Hydrotherosaurus alexandrae belongs to Hydrotherosaurus'
- 'Leurospondylus belongs to Elasmosauridae'
- 'Morenosaurus belongs to Elasmosauridae'
- 'Morenosaurus stocki belongs to Morenosaurus'
- 'Plesiosauridae belongs to Plesiosauroidea'
- 'Plesiosauroidea belongs to Plesiosauria'
- 'Pliosauridae belongs to Pliosauroidea'
- 'Pliosauroidea belongs to Plesiosauria'
- 'Polycotylidae belongs to Pliosauroidea'
- 'Polycotylus ischiadicus is recombined as Thalassiosaurus ischiadicus'
- 'Styxosaurus belongs to Elasmosauridae'
- 'Thalassiosaurus belongs to Elasmosauridae'
- 'Thalassomedon belongs to Elasmosauridae'
- 'Thalassomedon hanningtoni belongs to Thalassomedon'
- 'Thalassonomosaurus belongs to Elasmosauridae'