I would take any list of the largest sauropods with a grain of salt. Body mass estimates are extremely difficult to pin down, especially in a clade notorious for incomplete skeletons. Note also that different methods of estimating body mass can yield dramatically different mass estimates, as has happened in the case of Dreadnoughtus schrani. Volumetric estimates give it a body mass of roughly 20-40 tonnes, whereas scaling based on the size of its humerus and femur gives a much higher 60 tonnes. Comparing mass estimates found by these differing strategies is unwise, and I don't think Wikipedia has distinguished between strategies.
Alamosaurus also deserves to go on the list, as material from an indivudual in the same size class as Puertasaurus is known (Fowler and Sullivan 2011, APP 56: 685-690)
The giant Oklahoma Apatosaurus has not, to my knowledge, been assigned to A. ajax.
I'm not sure how good the data for Mamenchisaurus sinocanadorum is, either, as I don't know what data Greg Paul based his estimate on precisely.
I would like to ask, if the wikipedia table of largest/heaviest sauropods is currently valid and up-to-date (it doesn´t seem so)? Could it look like this perhaps? Thank you, Tom
1. Argentinosaurus huinculensis - 70 - 96 tonnes
2. Puertasaurus reuili - about the same
3. Unnamed Patagonian titanosaur - around 77 tonnes
4. "Antarctosaurus" giganteus - 40 - 80 tonnes
5. Notocolossus gonzalezparejasi - 45 - 75 tonnes
6. Apatosaurus ajax - 40 - 75 tonnes
7. Futalognkosaurus dukei - 50 - 70 tonnes
8. Mamenchisaurus sinocanadorum - 50 - 65 tonnes
9. Sauroposeidon proteles - 50 - 60 tonnes
10. Dreadnoughtus schrani - 40 - 60 tonnes